Archive | Testing and Tech

The euphoria about gravel bikes is hitting a snag: Many riders feel that their gravel bikes are slower than their road bikes. For example, James Huang, the technical expert from CyclingTips.com, posted:

“I’ve been spending too much time on gravel and mountain bikes lately. Good to be reminded what real speed actually feels like.” Continue Reading →

With wide tires, you can tune the ride of your bike to the terrain and to your personal preferences. This gives you options that simply did not exist in the past.
Gone are the days when we inflated our narrow tires to the maximum pressure and rode on rock-hard rubber. Even with narrow tires, you can lower the pressure a bit to get a (slightly) more comfortable ride. Of course, there is only so much you can do – the feel of the bike won’t really change. There is simply too little air, and you’ll get pinch flats if you reduce the pressure enough to make a real difference. The only way to transform the feel of a racing bike is to get different tires – that’s why professional racers have always run hand-made tubulars with supple casings (well, at least since the 1930s).
With wide tires, supple casings also make a huge difference. In addition, you can choose your tire pressure over a wide range: The 54 mm-wide Rene Herse Rat Trap Pass tires that Hahn is running in the photo above work great at pressures between 20 and 55 psi. That means you can cut the pressure to almost a third of the maximum, if you want. (For comparison, this is like running narrow 120 psi racing tires at 45 psi. Don’t try this with 25 mm tires!)

With wide tires, you can tune the feel of your bike by adjusting the tire pressure. The same tire will feel completely different depending on how hard you inflate it. This is something that you really start to notice with tires that are wider than 40 mm.

At 55 psi, my Firefly with its Rat Trap Pass tires feels firm and buzzy like a road bike on narrow tires. There is no noticeable flex in the tires, no matter how hard you corner, or how fast you sprint. You’ll feel every detail of the road surface almost unfiltered. The extra air does take off some of the harshness, and the extra rubber gives you more grip, but the feel is similar to a bike with narrow, high-pressure tires.

Why doesn’t the 54 mm Rat Trap Pass feel wallowy like a 25 mm tire at 55 psi? If you think of the tire as an air spring – a piston in a cylinder – then pressure is only one factor. The other is the diameter of the air cylinder. To compress a 54 mm tire takes more force than to compress a 25 mm tire, even if both are inflated to the same pressure.
Even with wide tires, you can get the feel of narrow tires, if you inflate them to (relatively) high pressure. But you also have options to tune your bike by letting out some air.

At first, not much is happening – 55 psi is far more than most riders will ever want to use in these tires. At 30 psi, you still get the firm feel of a ‘road bike,’ but more shock absorption and even better traction. This is the pressure I ride on very smooth roads.

At 25 psi, the tire has a lot more compliance. Now it really feels like an ultra-wide tire. It still corners great, but you can go over bumpy roads and really feel the suspension. This is the pressure I use on most paved roads.

On rough gravel, I let out even more air. At 20 psi, the tire really floats over the gravel. This is how I imagine a rally car with ultra-expensive shock absorbers feels: ‘breathing with the surface,’ gently going up and down over bigger undulations, but insulating you from the smaller bumps and vibrations. It’s an amazing feeling, and, without the bike bucking under you, you can put down power at all times. It’s fun to ride at ‘road’ speeds on rough gravel.
And even at this low pressure, there is enough air to prevent the tires from bottoming out. Even with tubes, I don’t get pinch flats – unless the terrain is really rough and rocky and speeds are ultra-fast.

When you’re descending at very high speeds on very rough terrain, you’ll have to increase the tire pressure a bit to avoid bottoming out too often. Even if you run your tires tubeless, you risk cutting your tires and damaging your rims if you bottom out too often and too hard.

When you return to pavement, 20 psi isn’t enough. The tire starts to squirm and run wide in corners. When you rise out of the saddle, it feels wallowy as it compresses under the thrust of your pedal strokes. And if you really push the limit, the tire can collapse in mid-corner.
Back on pavement, I inflate the tires back to 25-30 psi. If my ride includes both pavement and gravel sectors in quick succession, I often just keep the pressure around 25 psi, so I don’t have to mess with it.

Tire pressure is not just about shock absorption – it also affects the power transfer of your bike. A frame that is too stiff for the rider’s power output and pedaling style is harder to pedal – a little compliance smoothes out the power strokes and allows the rider to put out more power. We call this ‘planing,’ but it’s hardly a revolutionary idea.
Usually, that compliance comes from the frame. That is why high-end, superlight bikes perform so well, even on flat roads where the weight doesn’t matter. The lighter frames use less material, which makes them more flexible. Conversely, ultra-stiff bikes can feel ‘dead’ and hard to pedal to many riders.
With wide tires, that compliance can come from the tires, too. When we tested the Jones (above), we found it to perform wonderfully with its tires at ‘gravel pressure.’ When we aired up the tires for a fast road ride, the bike suddenly felt sluggish. This is the opposite of what conventional wisdom might tell you, but when we lowered the tire pressure again, the wonderful performance of the Jones was back. This has nothing to do with rolling resistance – it’s all about how much power we could put out thanks to the added compliance in the system. The Jones ‘planed’ best with its tires at relatively low pressure. This means that you can use tire pressure to adjust how much ‘give’ you have in your bike’s power transmission. I’ve found this a useful tool to get the most out of many Bicycle Quarterly test bikes.
Speaking of rolling resistance – don’t tires roll slower when you let out air? At least with supple tires, tire pressure makes no discernible difference, not even on smooth roads. As long as you have enough pressure that the bike is rideable, your tires roll as fast as they do at higher pressures. And on rough roads, lower pressures will be faster, both because the suspension losses are reduced and because you can put out more power.

Tuning your tires is fun. It optimizes your bike for your preferences and for the terrain you ride. Of course, tire pressure first and foremost depends on your weight – the numbers in this post assume a bike-and-rider weight of about 80 kg (175 lb).

Tire pressure also depends greatly on the casing of your tires. The values in this post are for Rene Herse Extralight tires. With Standard or Endurance casings, you can run about 10% less pressure. With a stiffer casing, you run even less air, all the way to airless tires that run at zero pressure. As your tires get stiffer, you lose the ability to tune your ride, because air pressure plays a smaller role in supporting the bike-and-rider’s weight. The beauty of supple tires is that air pressure is the main component that holds up the weight of bike and rider. This makes it easy to tune your tires.
Rather than inflate your tires to a set number, experiment with tire pressures to see how this changes the feel of your bike. Also remember that the gauges on pumps aren’t always accurate – use them only to replicate a setting that you’ve found useful in the past, rather than try to inflate your tires to an exact pressure. Once you’ve found values that work, you can quickly change the feel of your bike based on where you’ll ride and how you want your bike to feel. This makes cycling even more fun!
Further information:

• Why high pressure doesn’t makes your tires faster.
• Why supple casings run at higher pressures and still are more comfortable.
• Information about Rene Herse tires

It’s hard to believe that the first Oregon Outback, that incredible 363-mile gravel race, was just five years ago. It’s almost like we live in a different world now, so much has changed…

Back then, the idea of running a race that traversed the entire state of Oregon from south to north – on gravel roads! – seemed completely outrageous. So seemed the idea of riding the entire distance non-stop. And the idea of riding a road bike on these gravel roads. More than one rider told me at the start that they were astonished to see me on my Rene Herse for this grueling event. I am sure Ira Ryan, on his Breadwinner B-Road, heard similar comments.

A joyful crew rolled out of Klamath Falls on Memorial Day weekend in 2014. Most were on mountain bikes equipped with bikepacking gear. Nobody knew what to expect. Would it take two days or a whole week to reach the Columbia River at the other end of the state? There were few options for bailout; there was no support – this was a real adventure.

It did not take long for the race positions to shake out. By the time we reached Switchback Hill (above), there were three riders at the front. Ira Ryan was the favorite, having won the Trans Iowa race in his home state. He was riding on 35 mm tires – which was considered wide! Another strong racer was on a mountain bike. He had opted for narrower 700C tires. I was on the widest rubber, with our just-released 650B x 42 Babyshoe Pass Extralights.

I couldn’t match the speed of the other two, not helped by a broken hand that was still in a brace… With almost 300 miles to go, I settled into my own pace.

As the day wore on and the ground got softer, I could see Ira’s tracks swerving wildly from side to side. There was only one set of recent tracks, so I knew that the second rider had abandoned by now… Even on my 42 mm tires, I was struggling. And yet, on the (even softer) edge of the road, I could see the tracks of two mountain bikers who had come through here a few days earlier. Their wide tires had enabled them to ride in a straight line…
A few hours later, I reached one of the three towns on the route, where I met Ira Ryan’s camera crew. I learned that he was just 15 minutes ahead. Even though I had struggled on the loose surface, I had made up a lot of time – probably because my tires were wider.

The solitude of the long day on the road gave me time to think. I remembered how the Paris-Dakar Rally had fascinated me as a teenager. I could see parallels to the Oregon Outback: In the early Dakars, competitors used 4×4 trucks, which seemed the best vehicles to traverse the deserts of northern Africa. Then Porsche developed a four-wheel-drive version of their 911 sports car and won the Dakar in their first attempt (above).
Here in the Oregon Outback, it was obvious that the wide tires of mountain bikes provided an advantage on very loose gravel. Yet it was also clear that the mountain bikes themselves were holding back their riders on what really were roads after all. For the Dakar, Porsche had allied four-wheel drive with sports-car performance. Could we do the same and combine the wide tires of a mountain bike with the performance of a road bike?

By the time I climbed Antelope Hill, I had a plan: We’d take our all-road bikes beyond the 42 mm-wide tires that we’d been riding until then. I was certain that ultra-wide road tires would transform our bikes’ performance on gravel and other loose surfaces.

The last miles of the race went by in a blur. When I saw that Ira had written “Go Jan!” into the gravel, I knew I was on the home stretch. (Thank you, Ira, for encouraging me!)

After losing much time in the middle of the night – I back-tracked for more than an hour to make sure that I was on course – there was no hope of catching Ira. (He was faster anyhow!) My goal now was to finish in 30 hours. I redoubled my efforts and let the bike fly on the descent to the Columbia River.

I made my goal – and took the photo above after realizing that there was nobody at the finish. But I also wondered how much faster (and more fun) the ride would have been on wider tires.

Back in Seattle, I went to work on making road bikes with ultra-wide tires. My only concern was that nobody had ever ridden supple road tires that wide. Would they even be rideable? Or would the wheels bounce down the road like basketballs? Before we invested in tire molds, we needed to test this. So I asked the engineers at Panaracer in Japan (who makes our tires) to make prototype tires with our Extralight casing, using a mountain bike tire mold. A few weeks later, eight completely hand-made tires arrived. Now we had super-supple knobbies, but we wanted road tires.
The next step was to send the prototype tires to Peter Weigle, the famous framebuilder and constructeur. Years ago, he built a machine to shave the tread off tires, before we offered wide high-performance tires with just the right amount of tread. Peter shaved off the knobs to turn our prototype tires into slicks (above). The result were probably the most expensive bicycle tires ever made, but now we finally had 54 mm-wide, supple, slick tires that we could test.

Alex Wetmore had a 26″ bike that fit tires this wide, his Travel Gifford. We borrowed it and installed the new tires. If you look carefully, you can still see where the knobs were on the prototype tire above. It’s hard to describe our excitement: We were about to try something completely new.

Then we started testing the new tires. On gravel, the 54 mm-wide tires were amazing. The bike just cruised over stuff that would have meant serious ‘underbiking’ on 42 mm tires. It was fun!

What surprised us even more was the new tires’ performance on pavement. The grip was just incredible, both because there was so much rubber on the road and because the soft, supple tires no longer skipped over bumps. On this difficult descent in Leschi, you usually have to be cautious and brake for the bumpy turns. With the new tires, we pedaled as hard as we could, yet we weren’t able to reach the limits of grip. Did I say the testing was fun?

Knowing that the ultra-wide road tires worked as well as we had hoped, we ordered molds for two new tires: the Rat Trap Pass 26″ x 2.3″ and the Switchback Hill 650B x 48 (above). Both were revolutionary at the time, by far the widest high-performance road tires anybody had made in more than half a century. (Some very early pneumatic tires had been quite wide, too.)

There were no road bikes yet for such wide tires, so we worked with Firefly to make us a custom titanium road bike designed around the 26″ Rat Trap Pass tires. We took it to 13,000 ft (4000 m) on the Paso de Cortes in Mexico (above), where it performed even better than we had hoped. (Testing the new tires was definitely fun!)

26″ wheels make sense for tires this wide, but the 650B wheel size had more traction at this point – that is why we introduced tires for both wheel sizes. The next step was obvious: Bike makers needed an inexpensive OEM tire before they could commit to making bikes for tires this wide. As a small company specializing in high-performance components, this wasn’t something we were equipped to do.
Fortunately, others were taking note of our pioneering work. In 2016, WTB launched its Byway tires. Now there were ultra-wide 650B road tires at OEM price points. Bike manufacturers were quick to act, and before long, almost every bike maker designed bikes around this tire size. Today, the size introduced with our Switchback Hill tires has become a new industry standard.

It’s hard to believe that all this started just 5 years ago, with the first Oregon Outback, that incredible 363-mile gravel race.

• Watch Ira’s movie of the Oregon Outback.
• Riding back from the Outback to Seattle via the Cascade Mountains.
• More information about Rene Herse tires.

Winter riding is fun. The crisp air, the clear skies and the beautiful views. Getting out and breathing fresh air. There are many reasons to enjoy it.
Winter riding requires preparation. The most obvious is clothing – which we’ll leave for another post. Today, let’s talk about what makes a good winter tire.

Cold temperatures make rubber less grippy. There is no way around this. In theory, it should be possible to formulate rubber compounds specially for optimum grip in cold conditions. In practice, many ‘Winter Compound’ bicycle tires offer less grip in cold conditions, rather than more.
With all tires, you need to consider the reduced grip when it’s cold. Especially on familiar routes, it can come as a surprise when the grip suddenly bleeds away, at speeds that are well within the limits when the temperatures are warmer.

Having ridden many tires in cold conditions, I can say with confidence that the rubber compound of our Compass tires is among the most grippy you’ll find anywhere, cold or warm, wet or dry.

The chevron tread of Compass road tires helps to improve traction by interlocking with the road surface – which works regardless of the temperature. Even so, take it easy during cold days!

What about snow? Snow is surprisingly grippy. How much tread you need depends on the temperature: Cold snow requires only a chevron tread, like that of our road tires, to hook up. (You’ll see an imprint of the tire tread on the snow surface.) But when the temperatures are around freezing, the slushy snow is slippery, and you really need knobs to get good grip. (The knobs don’t hurt when it’s colder, either.)
Should a snow tire be wide – to float over the snowpack? Or narrow – to cut through the snow and try to find grip on the ground underneath?

Rally cars use narrow tires in snow. They are heavy and powerful, which allows their tires to dig down to a firm surface underneath the snow.

Snow cats use the opposite approach: Their wide tracks allow them to travel on top of deep snow without sinking in.

For bicycles, wide tires seem to be a better choice. Compressing the snow takes energy, and the less you sink in, the easier you roll. And cyclists don’t have enough weight and power to dig through the snow into the firm ground below.
What about ice? Under most conditions, only studded tires grip on ice. They punch holes into the ice that allows them to interlock with the surface. However, studded tires aren’t much fun to ride on dry roads. I suspect that a supple tire with studs wouldn’t work well – you probably need a stiff tire to push the studs into the (hard) ice.
There is one other issue: When it snows, many communities spread fine aggregate on the roads for better traction. Often, that aggregate contains freshly crushed rocks that can be very sharp and cause flat tires. In our area, we’ve found that the crushed rock will puncture worn tires – probably both because they are thinner and because aged rubber is easier to cut. Running relatively new tires has eliminated that concern for us.

If you live in a place that sees snow, but also dry roads, our dual-purpose knobbies are hard to beat as all-round winter tires. They roll as fast on dry roads as most racing tires. They corner as well as most road tires (above). And yet on mud and snow, they offer the grip of the best knobbies. Available in 700C x 38 and 650B x 42 mm, they are a great choice for rides where you may encounter all kinds of conditions.
Click here for more information about our tires.

At Compass, we see little point in replicating what you already can buy from others. When we made our first knobby tires, we wanted true dual-purpose tires. Could the new knobbies match the on-pavement of good road tires, yet grip as well in mud as true cyclocross tires. Impossible? You’ll never find out unless you try…

After a few seasons of cyclocross, there is no doubt that the Compass Steilacoom (700C x 38 mm) and Pumpkin Ridge (650B x 42 mm) offer plenty of grip and shed mud well – as you’d expect from their widely spaced knobs.
How about their on-pavement performance? I’ll let others speak on that. Matt Surch, the well-known Canadian gravel racer, wrote: “I don’t understand how the tread rolls so fast and quiet… these are wild!”

When BQ tester Mark tried them, he wrote: “Once the wind drowned out the tire roar at high speed, I was thinking about how unremarkable the Steilacoom tires had rolled on the paved descent. I had pretty much forgotten that I was riding on knobbies.” Yet he was glad to have them when a road closure detoured us via a muddy trail (above).

And now Mike Stead tested a set of Steilacooms for www.road.cc. Among other adventures, he set two Strava records on these tires. One was for a gravel descent. His comment: “I wasn’t even pushing that hard. […] The Steilacooms make you a better, faster descender than you deserve to be.”
The second KOM surprised not just him, but us as well: He set a new record for a flat-out 60-second sprint – on pavement. He wrote: “Averaging 45 kph, the Steilacooms made an awesome high-pitched noise as I fanged along the straight. Just to prove it wasn’t a fluke, I went back the next week and recorded exactly the same time to the second.”
Mike’s time on the Steilacooms was two seconds faster than the previous KOM record, which he had set on our Barlow Pass tires. Does that mean our knobbies are faster than our road tires? Not necessarily – there are too many variables – but it shows that they certainly aren’t much slower. And that is remarkable, considering that our road tires are among the fastest in the world.

In a future post, I’ll explain how we created a knobby that doesn’t ride like a knobby… until you hit mud or snow, when it behaves exactly like a knobby. But don’t take our word for it – read Mike Stead’s review.

In the 15 years of Bicycle Quarterly, one of our discoveries has been that testing bicycle performance isn’t easy, and that taking shortcuts often has led to erroneous conclusions.
Carefully designed tests that replicate what happens when real cyclists ride on real roads have allowed Bicycle Quarterly to debunk several myths. Certainly, the biggest change in our understanding of bicycles has been about tires.
Tires, more than anything else, change the performance, feel and comfort of your bike. We now know that fast tires can increase your on-the-road speed by 10% or more. But how do we know which tires are fast?

Lab testing is the most common way to test tire performance, usually on a steel drum (above). In the past, these steel drums were smooth. Now the testers have added some texture to simulate the roughness of the road surface. Unfortunately, that doesn’t address the fundamental flaws of drum testing:
1. The curved drum pushes deep into the tire

Since the drum is convex, it pushes deep into the tire, unlike a real road, which is flat. The more supple the tire, the deeper the drum pushes. This makes the tire flex more, which absorbs more energy. That is why a stiff tire performs well on the drum, and a supple tire does not. We know that the opposite is the case on real roads.

Increasing the tire pressure also makes the tire harder, and so the drum won’t push as far into the tire. That is one reason why drum tests show higher pressures rolling much faster (above). According to this data, increasing your tire pressure from 60 to 120 psi (4.1 to 8.3 bar) reduces the resistance by 30%!

Bicycle Quarterly‘s real-road testing (above) has shown that the opposite is true, especially for supple tires: They roll slower at 100-120 psi than at lower pressures. (Higher power = slower.)

This problem with drum tests has been recognized for a long time. There is a way around this problem, but it’s very expensive: Make the drum so large that it’s barely convex. One of the best drum testing rigs is in Japan, and from what I’ve heard, it measures about 7 feet in diameter. That means it’ll push into the tire much less, and thus it won’t make stiff tires seem faster than they really are.
On the other end of the spectrum, you have efforts to measure tire performance on small-diameter rollers,  like those used for training. That will always be futile: Anybody who has ridden on rollers knows how high the resistance is, because the rollers push so deep into the tires. And if you want to increase the resistance further, you just let some air out of the tires…
Not surprisingly, tests on small-diameter rollers show the ultra-supple Compass ‘Extralight’ casing rolling not much faster than the ‘Standard’ version. On real roads, the performance difference between the two is quite noticeable.

TOUR magazine in Germany has designed a test rig that eliminates the problems associated with the convex drums: Two wheels carry weights that are off-center, so they rock the wheels like a pendulum. This test rig rolls back and forth on a flat surface. You could even use it to test on real roads. The longer the test rig rocks from side to side, the lower the tires’ rolling resistance.

This test showed the Compass Bon Jon Pass as the fourth-fastest tire they’ve ever tested. (‘Rollwiderstand’ means ‘rolling resistance;’ the dark bars are for ‘rough asphalt;’ the light ones for ‘smooth asphalt;’ to convert the pressure from bar to psi, multiply by 14.5)
It’s interesting to compare the same tires – Compass Bon Jon Pass 700C x 35 mm tires (standard casing) vs. Continental 4000 S II in two tests:

• www.bicyclerollingresistance.com tested on a steel drum:
  • Compass (6 bar / 90 psi): 15.8 W
  • Continental (7 bar / 100 psi): 12.9 W
  • Conti has 18% lower rolling resistance.
• TOUR magazine used their rocking test rig:
  • Compass: 17 W
  • Continental: 17.5 W
  • Conti has 3% higher rolling resistance.
  • Compass is fourth-fastest of all tires TOUR tested (graphic above).

It’s clear that the drum test disadvantages a supple tire – the stiffer Conti performs much better. Adding to the confusion, www.bicyclerollingresistance.com gets lower resistance values than TOUR – it should be the other way around with the drum pushing into the tire.
There is another odd thing: TOUR shows the wider Compass tire in 4th place on the smooth road surface, but in 5th place on the rough surface, where it gets beaten by the narrower Conti rolling at higher pressure. That isn’t how it works in the real world, where the advantages of wider tires and lower pressures are greatest on rougher roads. That brings us to the second problem of these lab tests:
2. No rider on the bike

Without a rider, you have no significant suspension losses. Suspension losses are the energy that is absorbed when vibrations cause friction between the tissues of the rider’s body. Without a rider, there is nowhere to absorb the energy – steel weights don’t behave like human tissue.
Without suspension losses:

• vibrations wouldn’t slow you down.
• wider tires would be slower than narrow ones.
• higher tire pressure would make your bike faster.

On the road, with a rider on board, all these statements are false – because suspension losses absorb energy, and reducing suspension losses is key to making a bike go faster. Understanding suspension losses has revolutionized our understanding of tire performance. It’s the underpinning of the ‘wide tire revolution.’

The lab tests described above are like a return to the last century, when we all ‘knew’ that narrow tires rolled faster because they could run at higher pressures. So we ran 19 mm tires (above) and inflated them rock-hard for optimum performance. That was long ago – when did you last see a short-reach racing brake with so much tire clearance?
Today, even professional racers run 25 mm tire at 80 psi. They have found that this is faster, no matter what the steel drum tests say. Racers have concluded: When tests don’t replicate the real world, they aren’t of much use.
At least TOUR‘s test rig gives us some indication about the energy absorption in the casing. It neglects one half of the equation – the suspension losses – but it’s useful if we understand its limitations. On the other hand, tests on small-diameter drums are just misleading – because if you design a tire to perform well in these drum tests, it’ll have a stiff casing and ultra-high pressures. And that means it won’t perform well on real roads.
A better lab test?

Is there a way to design a realistic lab test for tire performance? After all, Bicycle Quarterly‘s test procedures – testing only on totally calm days; when temperatures are constant; with a rider who has trained to keep the same position for lap after lap – are fine if you are doing scientific research. But they are not feasible for commercial applications, where you need to be able to just mount a tire on a wheel, take it to the lab, and get an immediate reading of its performance – without having to wait until the weather is right, the wind has died down, and the temperature is constant.
At Bicycle Quarterly, we’ve been thinking about this. Current drum tests load the tire with metal weights that don’t absorb much energy as they vibrate. Is there another material that behaves similar to a human body? ‘Ballistic gelatin’ is used to simulate gunshot wounds in human tissue. It closely simulates the density and viscosity of human tissue. Using a material like that to weigh down the wheel might simulate the suspension losses.
Suspension losses vary with speed (higher/lower vibration frequency), so TOUR‘s rocking rig probably would not work – it simply moves too slowly to replicate suspension losses at normal cycling speeds.
That brings us back to the steel drums. You’d have to make the drum huge to reduce the problems with the convex surface. The drum surface itself would have to be a true replica of actual pavement, not just a diamond tread. You’d probably want to map a bunch of road surfaces with a laser and then use EDM (electrical discharge machining) to engrave an ‘average’ road surface into the steel drum surface. You could make interchangeable plates covering the drum with several road surfaces that feature different roughnesses. And why not a gravel road, too?
Validation

To validate your test rig, you’d take a fast, a middling and a slow tire, and test them on the road, just like Bicycle Quarterly has done. If your drum test results match those on the real road, then you can be confident that they replicate real-world conditions.
Back to Real-Road Testing

As you can see, making a useful test rig is a huge undertaking, which is probably why nobody has done it yet. For now, tire companies continue to develop their tires with the help of simple steel drum tests. That may be the reason why they don’t offer their supple high-performance models in truly wide versions: The steel drum tests indicate that you lose performance quickly as you run tires at lower pressures. And since supple, wide tires cannot support high pressures, steel drum tests suggest that wider tires should strong and not supple.
At Bicycle Quarterly, we’ll continue to test tires on real roads. To get good results, we can’t just put a power meter on a bike and go for a ride, then change the tires and repeat. We must keep the conditions the same for all tests. First, this means testing in a controlled setting, like a track. Second, we must control the variables tightly: test only on days with no wind and constant temperature, test each tire multiple times, and do a rigorous statistical analysis of the results.
The statistics are important, because there always will be some ‘noise’ – even in a lab test, because the tire warms up the longer you run it on the machines. The statistical analysis shows where you are recording real differences between tires and where you just see ‘noise.’
After more than a decade of testing tires under real-world conditions, we can say with certainty:

• Supple casings, more than anything else, determine the performance of your tires.
• Wider tires roll as fast as narrow ones on smooth surfaces, and faster on rough ones.
• Higher tire pressures don’t make the bike faster.

There is little doubt about these findings any longer – they’ve become widely accepted, even though the lab tests still haven’t caught up to the new science. But for us as riders, what matters is how well our tires perform on real roads, not on a steel drum.
Further reading:

• Bicycle Quarterly‘s tire tests are available as a 4-Pack of Back Issues.
• Compass tires were developed using the results of Bicycle Quarterly‘s tire tests.

From time to time, a customer will ask us: “How are Rene Herse and Compass tires different from Panaracers?” It’s no secret that Panaracer makes our tires – we benefit from the research and technology of one of the best tire makers in the world. Panaracer’s engineers know more about casings and tread rubber than almost anybody, and they translate our ideas into tires that outperform all others in their intended environments.
That also means that it may not be immediately obvious how our tires are different from Panaracer’s own tires, like the Gravelking – or even Panaracer’s budget model, the Pasela. At first sight, with tan sidewalls and black tread rubber, they can look very similar. They are even made in the same factory!

Recently, we had the opportunity to spend some time with Mark Okada from Panaracer Japan (right) and Jeff Zell from Panaracer USA (left). When I mentioned the Pasela, Mark just laughed: “They are completely different tires that have almost nothing in common.” 
I guess it’s the same as asking whether a Bugatti Veyron supercar has the same engine as a base-model Volkswagen Golf, since both engines are made in the same German factory…
What about the Gravelkings, which are available with a tread pattern similar to that of Compass road tires – evidence that the technology transfer between Compass and Panaracer goes in both directions. Jeff said that Panaracer gets the same question, and this is their reply:
“The Gravelkings and the Compass tires are two different types of tires. The reason that Compass tires are so successful is that Jan and Compass have a clear vision for what they want in a tire, and Panaracer has the technology to deliver that. The materials and the construction of the Compass tires vary from the Panaracer line, because of the performance that Compass wants to deliver to the customer. The components that go into the Compass tires, and the processes to make them, cost more, hence the price difference. Both are high-quality tires, but the ride and performance are different. If you’re looking for the most supple tire that incorporates all cutting-edge tire technology, you’ll choose Compass. If you’re willing to sacrifice the ultimate ride quality Compass is known for, to get a little more puncture and sidewall protection, then Panaracer has you covered there.”

Which tire is best for you really depends on your riding style and terrain. Natsuko rides her 30 mm-wide Compass Elk Pass Extralights on really rough gravel with little trouble (above), but if you are somebody who tends to get a lot of flats or destroys tires with rock cuts, we’d recommend the Gravelkings. As the name implies, they are designed for riding on rough gravel, which also means that they can be a bit overbuilt for riding on the road.
The Compass tires (above) are designed for riding on the road, but they also work well – and offer superior performance – on gravel, provided the rider lets the bike move around and doesn’t force it into rocks that could cut the sidewalls. It helps if you ride wide tires. Not only are they faster on rough surfaces, but their lower pressures also make the sidewalls less susceptible to cuts: the tire just deforms when hitting a rock.
Around here, we ride Compass tires – even on our Urban Bikes – because they offer world-class performance while being strong and durable enough for everyday use.
Click here for more information about Compass tires.

Long-time Bicycle Quarterly reader Matt Surch (above) put his name on the map when he won last year’s Steaming Nostril gravel race on Compass Bon Jon Pass tires. We checked back in with him to see how the tires performed in the year since then, and to hear about his road racing on Compass Cayuse Pass tires.
JH: With another season of riding and racing on the Bon Jon Pass tires, how do you feel about them?
Matt Surch: Frankly, the Bon Jons have been exactly what I’ve been hoping for in a gravel tire. This comes down to two key aspects: 1) volume – 35 mm is perfect for so much of the riding I do off paved roads. 2) tubeless – I love this format for its road feel and flat resistance. One of the things I’m really enjoying with the Bon Jons is that they are perfect for the rides where I head out the door without much more of a plan than to ride fun stuff. That tends to mean taking paved roads up to Gatineau Park, then piecing together spans of trail, some of which are very old dirt roads, in novel ways. I just go where I feel like going, try branches I don’t know, discover things. While the 32s are a bit small for rides like this, and the 38s bigger than required, the Bon Jons are the Goldilocks option: just right.
The Bon Jon has become my go-to for gravel, and I have them mounted on wheels that are on my cyclocross/gravel bike all summer. I have a pair of 32mm extralight Stampede Passes on another steel all-road bike for paved rides that I don’t need my aero road bike for.

Tell us about some memorable rides or races on these tires.
Sure, I have a couple that come to mind, from perhaps opposite ends of the spectrum. The first was our big annual local criterium in Ottawa’s Little Italy neighborhood, the Preston Street Criterium. This was the 44th edition of the race, which draws the best crit racers from Toronto and Montreal, in addition to our locals. I can still remember the first time I visited the crit, about 15 years ago, with my friend and longtime Compass tire evangelist, Rodd Heino. I barely touched my road bike then, and didn’t even consider racing.
I only took up racing criteriums in 2015, in fact, after waiting until I was sure I could ride at the front of the local training races as much as I needed in order to stay safe and learn the ropes. So last year, on Father’s Day, I raced the Preston St. Crit for the second time in the ‘Pro’ race. As I’d been doing all season, I was on the 26mm Compass Cayuse Pass Extralight tires on my Cervelo S5 aero road bike, mounted onto 55 mm-deep carbon Woven Precision Handbuilts wheels. This is a pretty aerodynamic set-up, and I’ve been very happy with this combination.
The race was pretty incredible. I missed the breakaway of 4 guys that went out about 30 minutes into the race, and decided to bridge up to them. One rider came with me, and we worked really hard together over the longest 8 minutes of my life to connect. The whole time friends and family were cheering me on so hard from the sidelines. I actually feel emotional as I write this….
We rode the rest of the race as a group of 6, ultimately lapping the field. Into the final turn I felt good and was positioned third, behind the two best sprinters. In an instant, I was sliding across the pavement. I’d slid out, not focusing enough on my cornering technique as we hit the final turn faster than any other lap. I lost a lot of skin and literally burned through my much-loved Giro SLX shoe, but my bones and bike were fine. My family found me, and they and a few guys from The Cyclery, one of Ottawa’s best bike shops, took care of me. I jumped back on my bike to salvage 5th, which was a bit of a consolation (I made a bit of money to help pay for repairs to my kit), but was just really happy to have delivered a peak performance that was only marred by one mistake. And having my family and everyone there supporting me was really special.

The other day that stands out was rather different. Iain Radford (fellow Compass devotee) and I decided to organize a gentleman’s race over an awesome road/off-road route at the beginning of July. Some of the most fun we’ve ever had on bikes has been when riding this format – teams of 4-6 riders team time trialling a big, hard route, unmarked, unofficiated – so we wanted to put one on. Our Ride of the Damned event is run in a team format, too, but it’s not a race. This time, we wanted to race.
We sketched out a route for a recon ride at the end of June and hit it up as a group of 4 on a rainy Sunday. I was on the 38 mm Compass Barlow Passes, Extralight (above), with Challenge latex tubes. I ended up with a tiny puncure on a rock, which I put down to the tubes being stretched so thin. The feel of the route wasn’t quite right, there was too much pointy rock on some of the sections of trail we used, which really interfered with the flow of the ride. We opted to tweak it, removing the pointy rock bits, and landed on a 117 km route that alternated between pavement, trail, and dirt road sectors.
On the morning of the event, El Camino, we had ten 4-man teams pre-registered, and we all headed off at roughly one minute intervals. My team was well balanced, and we leveraged our strengths well, riding mellow on the climbs, and absolutely drilling it everywhere else. It was a really hard effort on the bike, but so much fun! I’d opted to run the Bon Jons in tubeless format instead of the larger 38s with tubes, and this worked perfectly. Iain punctured, which saw us passed by a number of teams, then we chased them back down. It was exciting! At the end of the day we secured the fastest time, 3:51, beating our goal of 4 hours.
But the fun didn’t end there. We had everyone bring BBQ stuff, and got the grill at the park going for a great party after the ride. It was really simple logistically, and tons of fun hanging out after the ride as teams streamed in. Of all the racing I’ve done, this format is the most fun, I love it. Rather than a team working for one rider, everyone contributes to the whole team’s result. It requires a lot of strategy, it’s a bit of an art, like team trialing on the road, but more technical!

You run the tires tubeless. Any tips on how to set them up? What rims do you use?
Yes, I run the Bon Jons tubeless. I’ve had them on 55 mm-deep carbon Woven Precision Handbuilt wheels (above), which use a different tubeless bead design, so there has been a bit of a learning curve. The wheels are designed with a fairly deep centre channel for easy of tire mounting, with a tubeless bead shelf that has a lip on the inside, along the channel, for the tire bead to climb over when inflated. Early on, I realized that I needed a bit more tubeless tape than required for sealing the rim. I was having some trouble airing the tires up, which can be caused by a weak compressor or obstruction in the valves. I added another layer of tape (Gorilla tape, in fact) to see if that’d do the trick. It did, the tires mounted immediately when I beefed up the channel this way. So this is my #1 tip: if you don’t have a snug fit at the channel, add tape and try again.
The other tips are standard:

• Use a bit of water on the bead when mounting, it really helps. I don’t bother with soapy water, but just grab a bottle and drop some onto the tire.
• Remove the valve core of your tubeless valve when mounting the tire. I use the air-gun nozzle on my air compressor, sticking it into the valve. This allows more air to pass through.
• Don’t put sealant into the tire until you’ve mounted it. Trust me on this, you don’t want that stuff spraying all over you, it stains! Air up the tire, get the beads locked in, then use an injector to put sealant into the tire. I use one scoop of Stan’s regular formula sealant.
• You really need to shake the tires all over the place, especially on their sides, to get complete sealing. I’ll do that, then rest the wheel on its side for an hour or more, then flip it. This works well. Sometimes you actually need to ride a tire a bit to get it to seal. This isn’t a Compass-specific thing.
• If you don’t have an air compressor or access to one, yes, you can use CO2 to air up your tubeless tires. Obviously, this is wasteful and more costly than using a compressor. But it will work for a tire with a tight enough bead. DO NOT inflate with CO2 with sealant in your tire; the sealant will solidify into a ball. If you use CO2, let it all out after locking the beads, then replace with air.
• If you use a carbon rim, don’t overtighten your valves. If you do, you can deform the brake track, which you’ll feel under braking. Silca makes a nice valve set with a fairing that helps reduce the possibility of creating this deformation.
• If you don’t ride wheels you’ve set up tubeless often, your sealant will dry up sooner than if you ride it regularly. If you only use one scoop of sealant, odds are it’ll be mostly dry when you’re riding. You’ll want to make sure you keep some liquid sloshing round in the tires. Always bring at least one spare tube, two for more risky rides.
• Tubeless sealant really only seals small holes, like those from glass, thorns, wire. Medium-sized (a few mm long) can sometimes be sealed with the help of some cotton or similar fabric. Cut some small strips from scrap fabric at home (I’ve recently tried a cloth number plate/dossard) and pack them into your flat kit. If you puncture, try poking that fabric into your tire to create a dam for your sealant to seal around/soak into. This is best done while the tire is still fairly well inflared. I’d have this work, as have others, it’s worth a shot.
• You’ll need to air the tires up pretty high to get the beads to seat – this is normal. Bring the pressure back down to where you like it after seating the bead.
• Experiment with your air pressure. For very light tires like the extralight Compass Bon Jon, the sidewall is so compliant you’ll need a bit more pressure – with tubes or not – than you might imagine. Start on the firm side, then gradually drop your pressure during a ride until you find the best balance of ride feel you are looking for.
• Experiment, this is how you’ll get the most from your tires, and remember, tires cut more easily when their pressure is high.

Are you still on your first set of tires? Or if you replaced them, how many kilometers/miles did you get out of them?
I’m on my second set of Bon Jons now, but after 3000km my first pair are still rolling on my old bike. I mounted a fresh pair of the tan-walls on my new Brodie Romax (above) in the spring, and they’ve been perfect ever since.
Any durability concerns?
No, I have had no durabillity concerns whatsoever, I’ve been really pleasantly surprised. I find climbing is the toughest on tires for wear, and most of the climbing I do on this bike is on unpaved roads, which is why I think I’m getting quite good wear out of them. Because the tread wraps around the tire well, I don’t have any sidewall damage, which is somewhat incredible considering some of the trails I’ve ridden!
What tire pressure do you run? And how much do you weigh?
I weight about 172 lbs in the spring… up to about 177 lbs during the season. I used to run 50 psi rear, 47 front on the Bon Jons, but now I tend to run closer to 40. I spent a week in South Carolina riding big climbs and fast descents, and settled on about 55 psi in the 32 mm tires, which felt fantastic in the turns…

Our tires have a tread pattern that is optimized for road use. How do you find their grip on dry gravel?
Yeah, good question, I think this is something a lot of people are wondering about. I learned years ago at the Deerfield Dirt Road Randonnée that tread doesn’t do much for you on gravel. I rode 28 mm Grand Bois tires the first year there, then the 32s. Same tread, more volume with the 32s. On the descents, I didn’t have grip issues with either, but the loose climbs were always where the challenge lay. It was clear that more volume, more tread on the surface, was key. So I kept going up in size as I was able to get bigger tires on bikes, and confirmed that volume is all that matters for gravel. When the substrate is not locked in place, knobs have no effect. It’s like snowshoeing: all about surface area.
The tricky part comes when we need to deal with routes that have a mix of surfaces: pavement, gravel/dirt road, and trails. Trails, when gravelly, are fine with no tread. But knobs become useful if they have something to cut into. Slick patches of mud are an example. The standard Compass tread is scary on these, one has to ride completely upright. A bit of tread can cut through a bit of mud and dig into dry dirt below. On snow and grass, a little tread goes a long way too. At the Steaming Nostril race last year, we had some grass on the course, and I really had to use a lot of energy to keep moving with just the “Road” tread. But it was worth it! On the snow side – I know some are thinking, ‘What the….’ – the 2015 Rasputitsa Gravel Road race had an extended packed snow/ice sector that we absolutely HAD to use a file tread tire for. That was a shame, as the rest of the course would have been faster on the Compass tread.
On the El Camino route we capped things off with a very steep gravel trail climb, which kicks up to 23% in grade. With the Bon Jons I made it up, despite having no knobs on the tire. It was more a matter of smooth power transmission than tire grip.
When we face exposed rock, especially wet, we also tend to want some tread. A file tread tends to work well for this, as they have so many little edges.
I’ve recently spend some time on the 650B Switchback Hill 48s and 42 mm Babyshoe Passes, since my new cyclocross / gravel bike has disc brakes; I can run different wheel diameters. Both these tires climb really well on loose surfaces, due to their volume. That volume can also make them a little skittish on corners with pebbles over hardpack, which allow narrowed tires to cut to the firm surface more readily. That’s not a matter of tread, but width. I’m very much looking forward to trying the new Pumpkin Ridge 42mm 650Bs on mixed terrain, which will definitely work well in mud.

During the road racing season, you’ve been riding our Cayuse Pass 700C x 26 mm tires. How have those tires worked for you?
I’ve been riding the 26 mm Cayuse Pass tires on my Cervelo S5 aero road bike for almost two seasons now, and they have been somewhat transformative. Previously, I used Hutchinson’s tubeless tires on the bike, which were wooden, but reliable. In 2015, I used Continental GP4000s and Michelin Pro Race 4s. I punctured all but one of these tires badly enough to write them off. They were all 23 mm tires on my 19 mm (internal width) Woven wheels. While the Contis test very fast for aerodynamics and rolling resistance on rims like mine, in practice, I found them ill-suited.
The problem is that their tread – and this is true for the Michelins too – does no wrap around the casing enough to protect the tire’s casing. The tires handled well, somehow, but I had all kinds of flats on the shoulder of the tires. Because they were 23 mm tires (their 25s were too big for my frame/fork), they were somewhat squared off on my rims, and I had to run 100psi to avoid pinch flats. But this created too much casing tension, which makes it easier to cut the tire! In the spring, I was delighted to discover that the 26 mm Cayuse Pass fit my bike, so I’ve been on them all season. I experimented with pressure, working down from 95 psi to 80, where I’ve stayed. Wow, what a difference! I’ve got more grip, lower rolling resistance, and my bike feels so much more comfortable than it used to. I thought it would always suck on long rides, especially on typical roads with cracks, but I’ve found myself grabbing the bike so much more often, because it feels good. I’ve had only one flat on these tires in about 5,600 kms, a pinch on a pothole in the dark. I’ve still had no flats on the Bon Jons.
So, on top of being far more reliable than what I used to use on my road bike, I’ve found the Cayuse Passes roll really fast, and any aerodynamic hit I’ve taken as a result of them being a little wide for my rims and taking up more space within my frame and fork are outweighed by their fast rolling, grip, and reliability. I’m stoked to be on these tires, and don’t plan to change. I used to wish for a tubeless version of these tires, but now I am happy to stick with latex tubes. It’s hard to argue with no punctures in two years.
I wish I had a power meter, because I’d love to compare the Bon Jons on my CX bike against the Cayuse Pass. They feel slower on smooth paved roads, but I want quantification of the difference, ideall on the same bike. When it comes to our highest speed and intensity races, the crits and road races, I still feel I need to favour my system’s aerodynamics, and the 26s are the max I can fit in my Cervelo. But what if that bike was designed to be optimal with 28 mm, 30 mm, or 32 mm tires? Would it be as fast? I wish I could find out…
You’ve been trying the knobby Compass Steilcoom tires lately. How did that go?
I wanted to use the Steilacooms at the Steaming Nostril this year – our region was getting epic rain, and we experienced swampy conditions. But first I had to build my confidence in their pavement performance. I’d seen your post about them, so I was cautiously tentative. Results were good! I found that the faster I went, the better they rolled, as they sort of plane above 25-30 km/h, and really hum along around 40-45. We had some fast corners to deal with, one totally sand-covered, and I had zero issues. The profile really is great for cornering on the road. Ultimately, I was able to ride where I wanted to be and pull as long as I wanted to pull the whole time, and it was a total succes. I won’t make a habit of riding them for smooth stuff like this, but I am stoked that they are able to perform well on pavement, gravel and in mud.
You placed 2nd in this year’s Steaming Nostril. How did the Steilacoom tires perform in the actual race?
The Steilacooms performed really well in April at the Steamin Nostril. I had to make a tough call, between them and Bon Jons for race day. The region had seen a lot of rain leading into the race, and I was expecting the crux section to be waterlogged and slippery. Knowing that was where I’d want to break away from the front group and try to go on solo for the remaining 10k or sp to the finish, I opted for the Steilacooms. Ultimately, the section was quite dry, and I didn’t wind up needing the knobs. I managed to break away and went for it solo, but was fading into the wind as Sjaan Gerth pursued me, ultimately overtaking and holding me off for the victory. The Bon Jons would have been the faster tire on the day, but it was a game-time decision, and sometimes you just have to roll the dice and see. The Steilacooms were incredibly good in a few cyclocross races I did in 2016, and I remain really fond of them. I might just have to shave some down over the winter…
If we made a tire that isn’t in the program yet, what would you like to see from Compass in the future?
My dream tire, if I could pick just one, would be based on the Bon Jon casing (tubeless, same size), and add a file (diamond) tread. That would allow me to use the Compass tire for most of the gravel rides and races. The Continental CX Speed tread is probably the closest to ideal I can think of. There would still be some events that required more volume and tread, but a file tread would cover the bigger existing gap. It would also be a more sure-footed feeling tire for those less comfortable with a bit of sliding out there on unpaved surfaces!
We’ll consider that. Thank you very much, Matt, and good luck with the other races this season!
Further reading:

• Matt’s blog: http://teknecycling.com
• More information about Compass tires.

Photo credits:
All photos by Matt Surch, except:
1. Preston Street Criterium 2016
6. Rasputitsa Gravel Road Race 2016
7. Grégoire Crevier, Canadian Criterium Championships 2016

We’ve experienced a profound revolution in road bikes in recent years: It used to be that to go fast, you rode narrow tires and pumped them up to the maximum pressure. If you wanted more comfort, you used wider tires and (maybe) lower pressures, but you knew that you’d be slower.
Now we know that comfort and speed aren’t opposed, but inextricably linked: A bike that absorbs shocks better rolls faster. Narrow tires don’t have any speed advantage, and inflating your tires to the maximum often makes your bike slower.
But what does this means in practical terms, when it comes to choosing new tires for your bike? Do you need to get a new bike with clearances for ultra-wide tires? Or is there a way to benefit from the “tire revolution” on your existing bike?
The simple guidelines below are based on more than a decade of research into the performance of tires, and they’ve proven themselves on the road time and again.

Supple Casing
The most important part of the “tire revolution” is the supple casings. In the past, we thought that supple casings and wide tires didn’t go together well, because supple, wide tires have to be run at relatively low pressures. Now we know that lower pressures don’t make tires roll slower. And that makes a supple casing better in the two important areas of tire performance: A supple casing has less resistance as it flexes (hysteretic losses) and it transmits less vibrations from the road (suspension losses). It’s a win-win scenario.
Compared to the casing, all other factors – width, tread thickness, weight, etc. – are of minor importance. In Bicycle Quarterly‘s tire tests, the five fastest tires ranged in width from 24 to 36 mm, but they all had one thing in common: a supple casing. In practical terms, this means that a supple 25 mm-wide racing tire will be more comfortable and faster than a 42 mm touring tire with stiff sidewalls.
So don’t fret if your bike can only fit relatively narrow tires. Just get the best, most supple ones you can find, and enjoy most of the benefits of the “tire revolution”.

Width
When in doubt, use wider tires. At least up to 42 mm, wider simply is better. More grip, more comfort, same speed, fewer flats. What about the aerodynamics of wider tires? In our testing, both in the wind tunnel and on the test track, we found the effect too small to measure. And when you factor in the greater shock absorption (lower suspension losses) of the wider tires, it’s likely that any small increase in wind resistance is made up by the smoother rolling of the wider tires. On smooth roads, it comes out the same, on rough surfaces, wide tires are demonstrably faster.
Of course, you’ll have to work with the clearances of your bike. Don’t try to squeeze the largest possible tire in there with just a hair’s breadth of clearance. Your tire may “grow” with age or your wheel may go slightly out of true. I recommend a minimum of 3 mm clearance all around the tire. When in doubt which tire will fit, go with a slightly narrower one. If you find that you have more clearance than expected, get the bigger size the next time around.

Wheel Size
When you get a new bike, wheel size is an important consideration. Smaller and/or lighter wheels will be more nimble, larger and/or heavier wheels will be more stable. Ideally, your bike is both stable and nimble: It should stay faithfully on a chosen line, but it shouldn’t resist if you want to change its trajectory. How do you achieve that?
The forces of trail and wheel flop cancel each other, especially on a bike without a front load. That is why the wheel size plays such an important role – you can’t really compensate for a front wheel that is too large or too small.
The bike industry is only slowly waking up to this. Too many gravel bikes still come with the same 700C wheels that you find on racing bikes with much narrower tires. Smaller 650B wheels are a better choice for wide tires – from 40 to 50 mm –  and for even wider tires, I prefer 26″ wheels. That way, you can enjoy the nimble feel of a good road bike and the surefootedness of wide tires…
If you use ultralight carbon rims and superlight tires (like our Compass Extralights), you can go up one wheel size. The larger diameter compensates the light weight to keep the rotational inertia in the “optimum” range.

My “dream bikes” are equipped with either 650B x 42 mm tires (left) or 26″ x 54 mm, depending on whether they will see mostly paved or mostly gravel roads. But in practical terms, I am perfectly happy on a bike with 700C x 32 mm tires (right), provided the tires are supple performance models and not sluggish “touring” tires.

The importance of supple casings isn’t a new discovery. For almost a century, professional racers have ridden supple, handmade tires, no matter whether the fashion was for 30, 20 or now 25 mm-wide tires. In fact, tires are the only thing that hasn’t changed significantly on pro racing bikes during the last 70 years. You could put Fausto Coppi’s tires on Christopher Froome’s bike, and he’d never know the difference.
Outside the pro peloton, the importance of supple tires was largely forgotten as riders became more concerned about flat resistance than the joy of gliding along on a cushion of air. Only recently, supple clinchers have become available that offer the feel and performance of great racing tubulars, but in much wider widths.

Speaking of flats, that is the one drawback of staying with narrow tires. Since they run at higher pressures, they are more likely to puncture. And yet, in my experience, the fear of flats is often overstated. On the beautiful backroads that offer the best cycling experience, flats are relatively rare.
Debris accumulates where cars don’t go, hence you get so many flats when riding on the shoulders of busy highways. On backroads, you ride in the traffic lane (but with little traffic, you don’t bother anybody), so there isn’t much debris that could puncture your tires.

To summarize, you don’t need a new bike to enjoy the “tire revolution”. For your existing bike, choose tires with supple casings, and use the widest model your bike can fit with safe clearances. And when it’s time to get a new bike, consider getting a bike designed for wider tires and perhaps smaller wheels to get the performance of wide tires with the nimble handling that makes a good racing bike so much fun. It’s that simple!
More information:

• Blog post on determining how wide a tire your bike can fit.
• Information about Compass tires.

Photo credit: Goggles & Dust / Brett Horton Collection (classic racers).

It’s always interesting when bike industry people talk among each other, off-the-record. On the ride from the airport to Paul Camp a few weeks ago, one bike tester was still visibly shaken when he related: “My tubeless tire blew off the rim yesterday. I almost crashed.” Worried that this might have been one of our tires, I asked about the brand. He mentioned a big maker, known as a pioneer of  ‘Road Tubeless.’ The tester continued: “I had it inflated to 90 psi, well under the max. I was just riding along, when suddenly – bam!”
Tubeless tires are becoming popular these days. Using inner tubes inside your tire almost seems like a throwback to the 1950s. Cars have not used inner tubes in over half a century, and mountain bikes have gone tubeless, too. Many of us have been riding our Allroad bikes, with their wide tires, tubeless for years.
Finally, road bikes, with narrower tires, are going tubeless, too. But it hasn’t always been smooth sailing: There are more and more reports of tires blowing off the rims. What is going on? Why are tires with inner tubes safe at high pressures, but the same tires sometimes blow off the rim when mounted tubeless?

An inner tube doesn’t just hold air, it also reinforces the joint between the tire and the rim. Air pressure pushes the tube against the tire so that it no longer can move independently. For the tire to blow off, a very small section of the tube must stretch tremendously, so the tire can climb over the rim’s edge. As flexible as inner tubes are, they get to a point where they don’t stretch any farther – pull on a tube, and you’ll notice this. That makes it very hard for the tire to blow off the rim.
Without an inner tube, there is nothing reinforcing that joint. If the fit between rim and tire is even just the slightest bit loose, the tire can slide upward, and – bam! In fact, even with a perfect fit, there is a point at which a tire blows off the rim: Tire beads can stretch a little, and the higher you inflate the tire, the more force there is stretching the bead. That appears to be the root cause of the problem: Road tires typically are run at relatively high pressures.

Thinking about this, I realized that ‘Road Tubeless’ is a bit in uncharted waters: Usually, tubeless tires run at much lower pressures. Tires for cars and motorcycles are generally inflated to less than 45 psi. (The exception is airplane tires with up to 200 psi, but those are a very special design.)
All these tires also are much stiffer than bicycle tires, which helps them stay on the rim. A supple tire can move in just one small spot, which makes it much easier to climb over the rim’s edge. I was surprised at Paul Camp to hear about the tester’s experience with a tire that isn’t even known for its supple casing. But compared to car or motorcycle tires, even stiff bicycle tires are supple…

To test the limits of our tires with tubeless mounting, I installed a Compass Bon Jon Pass 700C x 35 mm tire on a wheel that we had measured carefully to make sure its diameter was exactly to spec. I inflated the tire to its maximum pressure of 90 psi (6.2 bar) – without problems. The pressure has already gone down to 85 psi by the time I took the photo – there was no sealant in the tire for reasons that will become apparent in the next paragraph.
I then inflated the tire further. 100 psi was fine. 105 psi, no problem. A few more pump strokes, about 108 psi, and – bam! The tire blew off the rim. I was wearing ear protection, and there was no sealant inside the tire, so no damage was done.
Of course, few people would inflate a 35 mm tire to 108 psi (7.6 bar). Even with tubes, the Bon Jon Pass is rated to a maximum of 90 psi (6.2 bar). And as long as everything is perfect, you can run them tubeless at this pressure, too. But in the real world, not everything is perfect. The diameter of different rims can vary considerably. We’ve found that the rims on many production bikes are a bit smaller than spec, because that makes it easier to mount the tires on the assembly line. Of course, this also results in a looser fit of the tires. If you build up the rim bed with extra rim tape – some mechanics even use thicker ‘Gorilla Tape’ – you can improve the fit of the tire on the rim.

Over the last year, I’ve been testing every model of tubeless-compatible tire in the Compass program. I’ve mounted them without tubes on a range of bikes, both Bicycle Quarterly test bikes and my own machines. I’ve experienced zero problems, but I also run them at pressures of 60 psi (4 bar) or lower. I remounted the Bon Jon Pass that blew off the rim and inflated it to 60 psi, put in some sealant, and took it for a couple of rides. As expected, it was fine. (However, we don’t recommend reusing tires that blew off the rim, as the bead can get damaged.)
Based on this experience, we recommend: Do not exceed 60 psi (4 bar) when running Compass tires tubeless. If you need higher pressures, please use tubes. Since the problems with running tubeless tires at high pressures are not limited to Compass tires, I’d recommend this for all tubeless tires – and especially for high-performance tires that are relatively supple.

However, you also don’t want to run too low a pressure with tubeless tires. If the tire flexes excessively, this will break down the casing until it starts to leak (above). With a narrow tire, you have a narrow window between “too high” and “too low” pressures. On a 35 mm tire, 60 psi (4 bar) still is plenty for most riders. (I usually ride my Bon Jons at about 35-40 psi.) But if we were to offer a 26 mm-wide tubeless-compatible tire, 60 psi isn’t enough even for a light rider. Yet going higher than 60 psi would risk blowing the tire off some rims.

With wider tires, you don’t have that problem. I run the 54 mm-wide Rat Trap Pass tires on my Firefly at 40 psi (2.8 bar) on smooth roads. At such a ‘high’ pressure (for tires this wide), the bike feels like a racing bike. On gravel, I can go down to 22 psi (1.5 bar) without risking damage to the casings. I run them tubeless now, after suffering two pinch flats during the Otaki 100 km Mountain Bike Race in Japan (above). As I found out, riding over really rough ground at very high speed will pinch-flat even 54 mm tires!
I feel that for riding on rough gravel, tubeless really is the way to go. Choose tires that are wide enough, run them at low pressure, and you shouldn’t have trouble. (Unless your rims are way out of spec.)
For road riding, the advantages of tubeless tires are less clear. Pinch flats are much less of an issue on the road, unless you still ride ultra-narrow tires. All the testing I’ve seen – including our own – indicates that the rolling resistance of tubeless tires is no lower, and perhaps even higher, than using thin, lightweight inner tubes. That isn’t surprising: You replace an ultra-supple inner tube with a liquid sloshing around inside your tire.
What about flats? One nice feature is that the sealant inside the tubeless tire automatically seals small punctures. You don’t have to go tubeless for that: Some riders use sealant inside their tubes. They report that it also seals small punctures in the tube – provided you use it from the start, when you mount a new tire. (With an old tire, during a puncture, the air may not escape through hole that is right above the puncture in the tube, but through a bigger hole from a previous puncture that is elsewhere in the tire. Then the sealant flows into the space between tire and tube, creating a mess without sealing the tube.)
Based on all of the above, we – as well as other tire makers like Pirelli – have concluded that at this time, running high-pressure tires tubeless isn’t worth the risks. Can these issues be resolved? It’s difficult to say. Perhaps ‘Road Tubeless’ is the way of the future, or perhaps it’ll be like radial tires for bicycles. Cars have used radials for decades, but for bicycles, they never caught on.
What needs to happen to make tubeless tires safe even at high pressures? Clearly, the interface between tire bead and rim must become more standardized, and manufacturing tolerances must become tighter. With a ‘perfect’ rim, it’s already fine to run our 35 mm tires tubeless at 90 psi, but how do we get all rims to be perfect?

For now, here is the take-home message for running tubeless tires:

• For tubeless, we recommend a maximum pressure of 60 psi (4 bar).
• If you are riding on gravel or rough stuff, tubeless eliminates pinch flats. And you’ll be running less than 60 psi anyhow.
• If you ride on the road and need more than 60 psi, use inner tubes. Not just with Compass tires, but with other brands as well.
• Even on smooth roads, Compass’ wide tires roll as fast as our narrow ones. Getting wider tires and running them at pressures below 60 psi is a good way to use tubeless on the road.
• When mounting a tire tubeless, first inflate it 20% higher than the pressure you’ll be riding. Let it sit for a while to make sure it will not blow off your rim. Then decrease the pressure before you ride the bike. That way, you know that you aren’t at the upper pressure limit for that particular tire/rim combination.

Tubeless technology holds great promise, but like everything, it should be applied where it makes sense and where it is safe. In a future post, we’ll talk about tips on how to set up Compass tires tubeless.
Photo credits: Nicola Joly (exploded tire), Cyclocross Magazine (damaged casing), Toru Kanazaki (Otaki 100 km Race)

“Don’t do this on knobby tires!” would be most cyclists’ advice when looking at the photo above. Everybody knows that cornering hard on pavement and knobby tires don’t go together.
And yet, the photo shows me on Compass Steilacoom knobby tires. And I didn’t take any undue risks. It was a cold winter day, and the pavement was still moist from a recent snowfall, so I didn’t push the limits, and the tires always had plenty of grip in reserve. (I apologize for the blurry photo – there wasn’t enough light for high-speed photography on this dark winter day.)
We took this photo during an all-paved ride around Mercer Island – a fast-paced route with many corners and subtle (and not-so-subtle) ups and downs. It’s a challenging course to ride fast. And it’s even more challenging when riding with my friend Ryan, who trains here several times a week and knows every inch of the road.
I rode a bike with Compass 700C x 38 mm Steilacoom knobbies (above), because I wanted to find out how well they perform as dual-purpose tires.

After a full season of cyclocross, we already know the Steilacooms work great on mud and loose surfaces… What about rides that are mostly on pavement, but include enough muddy trails that you’d want some knobs on your tires?
I had always been bothered by how terrible my cross bike felt on the few paved sections of the race course. Those sections rarely measured more than a few meters, but if there was a corner, I had to take it carefully. Annoying when I really wanted to go all-out. I figured that there had to be a better way. And when designing the Steilacooms, we thought hard about how to make a knobby perform well on pavement, too.

How do you make knobbies that perform well on pavement? We designed the tread pattern together with the engineers at Panaracer. They were excited to bring all their knowledge to the project, with no concern about “what people expect a knobby tire to look like.” Together, we spent a lot of time thinking about knob shapes and spacing, and how the tire transitions from one knob to the next.
The key difference to previous knobbies is that we didn’t look at each knob individually. We treated them as a system that interacts, not just as the tire is rolling forward, but also as it leans into a turn. We made sure that there always is the same amount of rubber on the road, not sudden changes as you transition from one row of knobs to… sometimes almost almost no rubber at all.
We also discussed knob sizes with Panaracer’s engineers. They have to be small enough to dig into the mud, but large enough that they don’t fold over during hard cornering. It’s not rocket science, but it requires visualizing what the tire will do as it rolls and corners.
On the Steilacoom, you don’t fall off one knob and then climb onto the next, so the tires roll more smoothly than most knobbies. And the knobs are big enough that they don’t squirm, which also helps with your speed and cornering.

I had high expectations for the Steilacooms, but even I was surprised how well they perform on pavement. On that ride around Mercer Island, I had no trouble keeping up with Ryan, even though he was riding his new titanium bike with smooth Compass Babyshoe Pass Extralight tires. The Steilacoom knobbies did not just perform well on the straights, I also didn’t lose any ground in the corners. Of course, this doesn’t prove that the Steilacooms roll quite as well as the Babyshoes, but if there is a difference, it is much smaller than I anticipated.
During our next “BQ Team” ride, I switched bikes with Mark. At first, he was reluctant. “Why would I ride knobbies on the road?” he asked. But then he, too, was surprised. He said: “When you hear the knobs sing on the pavement, you think the bike will be slow. But on the downhills, the wind drowns out the tire noise, and then you realize that they perform pretty much like a good 38 mm road tire would.” And this from the guy who had sworn off knobbies for good when he designed his 650B randonneur bike.
Now, we understand that many readers will be skeptical when a maker claims that their new tire revolutionized how well a knobby tire rolls. So we took a few photos… with a little tree to show that we didn’t just tilt the photo to make it look more dramatic. The Steilacoom really raises the bar beyond what even we thought possible.

The optimized arrangement of knobs is only part of the story. Just as important for the Steilacoom’s speed is the supple Compass casing. The result is a knobby tire that is faster than most slick road tires.
Are there drawbacks of the Steilacoom tread pattern? Of course, otherwise, we’d all ride knobbies from now on. First, once we test them on the track with a power meter, I fully expect that they will roll a little bit slower than our other tires. That is unavoidable, but the difference is too small to notice on the road. That is pretty remarkable.
The knobs also add weight to the tire. And the bigger you make the knobs, the heavier the tire gets. Thanks to our lightweight casings, the Steilacoom still isn’t a heavy tire, but it weighs about 30 g more than our Barlow Pass with smooth tread. This won’t slow you down much even when climbing mountain passes, but if you don’t need knobs, why carry the extra weight?
Like all knobbies, the Steilacooms tend to wander a bit while going straight. You are rolling from one knob to another, rather than on a continuous tread. Again, it’s not a huge deal, but if your ride doesn’t require knobbies, I would pick one of the other Compass tires with their road-optimized tread. And finally, there is more noise from the tires as they roll. But compared to other knobbies I have ridden, all these disadvantages are very subdued.

The Steilacoom’s excellent pavement performance opens up completely new rides. Imagine you are heading into the mountains and expect muddy sections along your course, but most of the ride will be paved. No problem with the Steilacooms. They will make short work of the mud, without holding you back on the paved portions of your ride. That makes the Steilacoom the ultimate multi-purpose tire.
Click here to find out more about the Steilacoom 700C x 38 mm tires.
Photo credits: Ryan Hamilton (Photo 1, 4), Heidi Franz (Photo 2), Duncan Smith (Photo 5), Hahn Rossman (Photo 6).

Compass has long championed the use of “road” tires on gravel. More and more gravel racers agree: When gravel is sliding on gravel, knobbies are of little use.
So then why does Compass offer a knobby tire, the Steilacoom 700C x 38 mm? Knobs are useful in mud. They dig into the surface, and since the mud is viscous (gooey), it provides something for the knobs to push against. That is why cyclocross bikes use knobby tires.

It’s important is to space the knobs widely, so the mud is ejected as the tire rotates. Otherwise, the tire just clogs up, and soon you are riding on slick tires again, except that their tread is made of mud instead of rubber. What you want is a muddy bike, but clean tires (above) – the tires pick up mud only briefly before it is flung off.

Snow is a different story again. Depending on your speed, it behaves differently. At high speeds, you glide through the snow almost as if you were skiing, and tread patterns make little difference. At low speeds, you compact the snow and create the surface on which you ride. Knobs dig into that surface and give you extra grip. Even a herringbone tread works OK. Slick tires or longitudinal ribs act like the runners of a sled – they just slide and offer very little traction.

What about ice? Ice is too hard for rubber tread to dig into. You need metal studs that bore into the ice to find traction. Sometimes, snow compacts to ice (above). I prefer to walk rather than risk a fall when I see ice on the road. (Unfortunately, I don’t know of a good method to see “black ice” before it’s too late.)

Back to mud, where knobbies make the biggest difference: Designing a good mud tire isn’t hard – space your knobs widely, and the tire will self-clean as it rotates. The downside is that it’ll be buzzy and slow on pavement. I love the FMB Super Mud tires (above) on my old ‘cross bike (our Steilacooms don’t fit!), but their secret isn’t in the tread pattern – the extra-supple casing makes them wonderfully fast and contributes to their great traction. The tread is incredibly buzzy on pavement. It’s good that most ‘cross courses include no more than a few meters on pavement.
The knob shape itself makes little difference. “It’s all about ‘design'” a Panaracer engineer confided.
Designing a knobby tire that rolls OK on pavement is not too hard, either. Space your knobs closely, and the tire will roll fine. But when it gets muddy, the tire will clog up, depriving you of the advantages of a knobby tire. You get only the disadvantages of knobbies, without many of the benefits.

Designing a tire that rolls well on pavement and grips well in mud is much harder. If you also want the tire to corner well without knobs folding over and suddenly losing traction, it seems almost impossible. And yet… with the engineers at Panaracer, we spent a lot of time analyzing and testing knob designs during the development of our Compass Steilacoom 700C x 38 mm knobbies. We found a few things that can greatly improve a knobby’s performance on pavement, without detracting from its ability in mud. More about that in a future post…
Click here for more information about Compass tires.
Photo credit: Wade Schultz (bottom photo)

We thoroughly test every Compass product before we release it. We also seek unbiased evaluations from experienced riders who weren’t involved in the development of the products. For the new Compass Steilacoom cyclocross tires, we gave them to a number of cyclocross and gravel racers. Two of them have reported back in detail, and we are happy that they like the new tires even more than we do. Matt Surch (above) is one of the fastest gravel racers in Ontario. Wade Schultz (below) is a Category 2 ‘cross racer from Seattle.

Both liked the performance on damp surfaces and mud – Matt commented: “The grip is fantastic, allowing extreme lean angles” – but that was to be expected on a tire with big, widely spaced knobs. What surprised them both was the excellent performance on pavement.

Wade: I expected these tires to be appropriately slow on smooth pavement, but was frankly surprised by how well they did. Their rolling resistance is lower than other pure mud CX tires (tight center knob spacing helps). I love the excellent transition from center to side-knobs. I did not experience any on/off traction vagary on corner lean initiation.
Matt: My Woven rims have a very good tubeless bead shelf and inner ridge that holds the bead in place. They mounted easily, and I went out for a cx rip. Wow! Seriously, I didn’t expect this tread to roll so well. Yes, it’s pretty close to linked in the centre, but with so much open space, I thought they’d feel slow on pavement. Nope. Instead, they just feel like they roll sort of crazy fast, like faster than they should.
This isn’t a complete surprise – much thought and development went into the spacing of the knobs. We didn’t want to space them so close that they’d clog up and no longer grip on mud, but we alternated them in a way that keeps the tire supported, rather than have it bump up and down as the knobs pass underneath.

The other question is what tire pressure is ideal for these tires? Matt tested the absolute minimum he could run:
Matt: I took pressure down to 27, which was low enough to fold the rear on off cambers and fold the front on some soft to hard transitions. This is the same sort of folding I’d expect from my tubulars, and I figure if I can get a tubeless tire to fold but not burp, I’m good. I lost no pressure at all after 40 minutes of trying to get them to burp. And this is minutes after mounting.
A minor note of caution: Running your tires at pressures this low gives you the ultimate in traction for cyclocross racing, but it can reduce the life expectancy of the tires, as the casings are under a lot of stress when they fold over.

Matt raced the tires in the first races of the season. He reported after the first one:
Matt: My experience through the 60 minutes of racing was overwhelmingly positive. I didn’t feel at 100% physically at the start, yet I had my best cx race I can remember, finishing closer to a few adversaries than ever before, for 4th overall in the Senior / Master 1 race.

It’s exciting that the tires work as well as we had hoped. A lot of thought went into that tread design – it’s much more than just a few widely spaced knobs – and we are glad that the tires offer the on-pavement speed and smooth cornering that we wanted to achieve. Here are the final words from these two experienced racers:
Wade: Is my satisfaction with this tire linked more directly to the casing volume (vs traditional cx tubulars) or the tread design? [I suspect the answer is: Both.]
Matt: I am extremely happy with them. Congrats on making an awesome tire.
Further info:

• More information about the Compass Steilacoom cyclocross tires.
• Matt’s complete report of his experience with the Compass Steilacoom tires on his blog.

Photo credits: Andrea Emery (Photos 1, 4, 5); Heidi Franz (Photos 2, 6) Alain Villeneuve (Photo 3).

Congratulations to Andreas Behrens of LaFraise Cycles for completing the amazing Transcontinental Race. Riding unsupported for almost 2,400 miles (3900 km) over a course that traversed all of Europe, Andreas completed the non-stop race in 15 days and 12 hours.

The course traversed the highest mountain ranges of Europe – above the view from the Grimsel Pass to the Furka Pass in Switzerland. All in all, Andreas climbed more than 40,000 m (130,000 ft).

Andreas builds bikes himself. The one he rode in the Transcontinental Race was equipped with Compass Loup Loup Pass Extralight 650B x 38 mm tires. After the finish, he sent us photos of his tires:

Even after 4000 km, the front tire still has plenty of life left.

The rear tire is a bit more worn. The wear is almost entirely in the center of the tread – an indication that Andreas is running slightly higher tire pressures than we’d recommend. He might be more comfortable and even faster if he let out a tiny bit of air.

When he dipped his wheels into the Dardanelles at the finish in Turkey, he hadn’t suffered a single flat tire!
Andreas isn’t a sponsored rider – he bought the tires with his own money. I asked him why he chose Compass tires. His response:
“I have a few bikes with wider tires, between 32 and 42 mm. From experience, I knew that on these bikes, I wasn’t any slower than other riders on their racing bikes. In the past, the tires from Panaracer and Grand Bois always felt a bit stiff. When I visited JP  at 2-11 Cycles [Compass’ French importer], I had the opportunity to test the Compass tires. I liked the ride very much and decided to use the 38 mm version on my bike for the Transcontinental Race.
“Of course, it also was a test to see whether the Compass tires would survive the race. I only recommend products to my customers that I use myself. My experience confirms your testing: the tires reduce vibrations and fatigue. Of course, it wasn’t only the tires: The steel frame, custom geometry, comfortable saddle and ergonomic handlebars helped me finish the race without soreness or injury. No saddle problems, no numb hands, even though I mostly rode without gloves. I credit the comfort of the bike.”

Riding from Belgium to Turkey, all the way across Europe, without any major aches and pains – that is truly inspirational. Congratulations!
Click here for information on Andreas’ bikes: LaFraise Cycles.
Photo credits: Andreas Behrens (LaFraise Cycles).

It’s no secret that we love cyclocross. It was only a matter of time until Compass Cycles would introduce a ‘cross tire. Like all our products, the new Steilacoom fills a need that currently isn’t being met: a supple, wide ‘cross clincher that is tubeless-ready and that approaches the ride and performance of my beloved FMB ‘Super Mud’ tubulars.
The Steilacoom is named after an iconic ‘cross course near Seattle. It’s where I won my first cyclocross race on a course that (back then) featured a daunting descent and a brutal run-up. What makes the new Compass tire special is its width: 38 mm is wider than most ‘cross tires.

Some will argue that the UCI limits ‘cross tires to 33 mm. True, but most of us don’t race in UCI-sanctioned categories. In the U.S., this rule appears to apply only to the national championships. If you are competing at that level, you probably already have a bunch of FMB or Dugast tubulars and expensive wheels to glue them onto. For the rest of us, the UCI rule is irrelevant, yet most ‘cross tires are limited to a maximum width of 33 mm. If you ride clinchers, this is less than optimal.
To provide the same traction and comfort, a clincher needs to be about 10-15% wider than an equivalent tubular. Scaling up a 33 mm tubular gets you a 38 mm clincher. This tire still fits into most current cyclocross frames – no need to go ‘monster-cross’ to fit the new Steilacoom tires.
The Steilacoom ‘cross tires are available with our Extralight casing that usually is used for handmade tubulars. It’s one of the best, fastest-rolling casings anywhere. For those on a budget or with a propensity to cut their tire sidewalls, we also offer them with the Standard casing that still offers superb performance. The Steilacoom tires are tubeless-compatible – that is, they are designed to be used with tubeless rims and sealant. Of course, you also can set them up with tubes.

What about the tread pattern? It’s based on more than 20 years of experience racing cyclocross. The 1996 newspaper article above shows me at the very first collegiate cyclocross nationals ever held in the U.S., with my Alan – the bike I still race today.

Back then, cyclocross tires were quite simple: The best ones used a tread pattern that consisted of round knobs. Key was to have them spaced widely enough so that they didn’t clog up with mud. Traction was great – I just wish they had been wider than the 25 mm or so that they measured. (It’s incredible that back then, we raced ‘cross on tires as wide as those that the pros use today on the smooth roads of the Tour de France!)
When I discussed tread patterns with the engineers from Panaracer, their opinion was succinct: “With knob shapes, it’s mostly about fashion.” I thought about that and realized that the old round knobs made a lot of sense: You don’t want the tread to clog up with mud, so the fewer edges you have, the harder it is for the mud to stick to the tire. A round knob has the smallest surface area for mud to stick.

Panaracer’s engineers cautioned that round knobs might slide through the mud too easily. A straight edge provides more traction. That is why our knobs are square, with rounded corners. That way, the knobs present straight edges for the forces of pedaling and braking (front/back), as well as cornering (right/left). It’s logical.
What matters more than the knob shape is their size and especially their pattern on the tire. We placed the knobs so that there are a few more in the center. The square knobs are harder to deform than thinner, irregular shaped ones. This reduces the squirm on hard surfaces. The knobs are placed so that the transition from the center tread to the shoulders is smooth and gradual. The slightly larger shoulder knobs resist squirm during hard cornering. That way, the tire rolls smoother and corners better on hard-packed dirt and pavement. The first rides by cyclocross racers have confirmed this: On pavement, the Steilacoom exhibits none of the sudden breakaway that you get with most other knobbies. Many riders will want to use these tires for mixed-surface rides where they expect significant mud.
What has been most surprising during our testing of the prototype Steilacooms is how well the new tires roll and corner on pavement. We always intended the tire as a dual-purpose tire that excels on all surfaces, paved or not, but we weren’t sure whether it was possible to create a knobby that excels on pavement, too. At the same time, they shed mud like my FMB ‘Super Muds,’ which is about the highest benchmark we can imagine. The ride is as great as you’d expect from our supple casings, and the knob pattern delivers on its promises.

I can’t wait to race on them. I have a (slightly) more modern Alan with clearance for tires this wide. Now I just have to build it up with a set of tubeless rims!
Click here for more information about the new Steilacoom tires.
Photo credits: Heidi Franz (top); Wade Schultz (second from bottom), Leander Vandefen (bottom).

Over the last few years, the idea that higher pressures don’t make your bike faster finally has become accepted. Many cyclists now run lower pressures to improve comfort and traction, without giving up anything in speed.

On gravel, lower pressures actually make you faster, since the bike bounces less. On soft gravel, like we encountered during our ride across the Paso de Cortés in Mexico (above), lower pressures (and wider tires) allow you to float on top of the surface, rather than sink in. Again, that makes you faster and more secure.

So lower pressure is better in many cases, but how low can you go?

Here is a detail from the photo of Hahn on the Paso de Cortés. You can see how long that contact patch is – there is a lot of tire on the ground, which spreads the rider’s weight over a larger surface area.

Yet the pressure is not too low. The tire still holds its shape: Seen from the side, the tire sidewalls form a nice circle. That is the reason why it still rolls as fast as it did at higher pressures: The flex in the tire is limited to a relatively small area.

Only when viewed from above, can you see the contact patch bulge outward – but even that should not be excessive.

What happens if your tire pressure is too low?

1. The tire can collapse when cornering. During our Mexican adventure, we pumped up our tires when we reached pavement, so we could tackle the fast and twisty descent with confidence (above). Even on gravel, a tire can collapse under the forces of cornering, if it’s not inflated high enough.
2. You can pinch-flat, if the tire bottoms out, and the tube gets crushed between rim and road surface.

3. The tire can get damaged. When the tire gets kneaded too much with each revolution, it’s not only slower. (Yes, lower pressures do get slower at some point.) It also puts very high stresses on individual threads of the casing, which then can break. The tire needs a certain pressure to hold its shape and distribute the stresses uniformly over all the threads in the casing.

In the photo above, you can see a cross-hatched pattern where the casing threads have broken. This tire was tested by a magazine, and they rode these 35 mm tires at extremly low presssures of just 35 psi (2.4 bar).

The tire probably is still fine to ride, but if you try to run it tubeless, air (and sealant) will seep out of the tiny holes caused by the broken threads. (The sealant colored the sidewall where it leaked.) If you see a single zigzagging line in the tire sidewall where one thread has broken, increase your air pressure slightly to prevent further damage.

What is the minimum pressure that is OK to ride?
This depends on many factors, including:

• Rider weight. Obviously, heavier riders need to run higher pressures to prevent the tires from collapsing.
• Surface grip: The more grip you have, the higher are the forces generated during cornering. To withstand those forces, your tire needs to be inflated harder.
• Tire construction: A stiff tire is held up by its sidewalls as much as by the air pressure inside. A supple tire’s sidewalls do little to support the bike’s weight, so you need higher pressure. Thanks to the supple sidewalls, this tire still is more comfortable and faster, even at the higher pressure.
• Riding style: A rider who has a round spin can run lower pressures. If your bike starts to bob up and down with each pedal stroke, your tire pressure is too low. Fast riders need to run slightly higher pressures, since they hit obstacles with more force. And riders who corner on the limit need higher pressures to prevent the tire sidewalls from collapsing.

I polled the riders on the Bicycle Quarterly team about the tire pressures they ride. I was surprised how consistent they are. Some riders are a bit heavier and use a bit more air, so we equalized the values for weight of 82 kg / 180 lb.

Or if you prefer metric values:

Of course, we’ll adjust these values if needed, for example, on rough gravel, we increase the pressure to prevent pinch flats… And remember that different pressure gauges can vary by up to 15%, so your 45 psi may be quite different from our 45 psi! Still, this provides a starting point for thinking about the right tire pressure.
For the majority of riders today, the advice “When in doubt, let out some air!” still holds true, but as we lower our tire pressures, we need to be aware that too little air also can cause problems.
Further reading:

• Tire Pressure Take-Home: A basic guide to tire pressure and how it affects your ride.

Photo credit: Cyclocross magazine (damaged casing)

“Buy the nicest, most supple tires you can afford; and buy them in the widest width that you can fit in your frame.”
That is Joshua Poertner’s summary of a panel discussion on Cyclingtips.com. Joshua used to be the president of Zipp, the makers of super-fast aero wheels, and he did a lot of research on how to make your bike faster.
The panel included Joshua, cycling journalist James Huang, and me, with Elden Nelson (who runs the blog “The Fat Cyclist”) moderating. The goal was to explain the science behind the current trend toward wider tires to an audience of racers and performance riders, who want to understand how to make their bikes faster.
In the podcast, we talk about why narrow tires feel faster, but aren’t. We discuss how lower pressures increase the internal resistance as the tire flexes, but decrease the suspension losses from the vibrations of the bike – the two effects cancel each other, hence your speed doesn’t change.
We also talk about the history of this research. I was amazed to find out that Zipp had been doing similar research to our own. They were trying to optimize tire pressures for the professional racers they sponsored. During their testing on rough surfaces like the cobbles of Paris-Roubaix, lowering tire pressure made their racers faster – until their wheels broke. The next step was to go to wider tires, so the wheels could survive… And then they found that even on smooth roads, lower pressures and wider tires were faster. They considered these findings “trade secrets”, and yet the other teams just had to read Bicycle Quarterly to get the same information. And eventually they did…
To me, Joshua’s conclusion really is remarkable: “Buy the most supple and widest tire you can fit in your frame.” His words could just as well have been mine. To have the guy who designed wheels for Zipp say this… It shows that the wide tire revolution has reached cycling’s mainstream.
Click here to listen to the entire podcast.

How does it work that wide tires are as fast as narrow ones? It is really simple:

Comfort = Speed

When your bike vibrates, energy is dissipated as friction. That energy must come from somewhere – it no longer is available to propel the bike forward, so your bike slows down. That is why your bike rolls faster on smooth pavement than on rough chipseal.

At Bicycle Quarterly, we started testing tires on real roads, with a real rider, in 2006. We found that higher tire pressures don’t make your bike faster. Back then, that was pretty revolutionary. Previous tests on smooth drums had shown that the harder you pumped up your tires, the faster you went. But smooth steel drums aren’t a good model for what happens on real roads, and the results were misleading.

Over the last couple of years, our findings have become generally accepted. Most tech writers now talk about vibrations that slow down your bike. The missing piece is: How do vibrations slow you down? The most common explanation is that your bike goes up and down as it vibrates. All that climbing adds up and costs a lot of energy.

It’s true that vibrations slow you down, but it’s a bit more complicated. Energy cannot disappear. The only way to ‘lose’ energy is to convert it to heat through friction. When you climb a mountain pass, you put in energy as you gain elevation. As you descend on the other side, you get some of it back – you can coast downhill without pedaling – but most of it is converted to heat by your wind resistance. During the descent, your bike accelerates until you reach ‘terminal velocity,’ where the energy input from the elevation loss equals the energy consumed by wind resistance.

That explains where the energy goes when you cross a mountain pass. It cannot explain what happens when your bike vibrates on flat roads.

We tested various equipment on rumble strips to get a maximum value for the energy that is lost to vibrations. We found that riding on this “very rough” road can take up to 290 Watt more power than riding on smooth pavement at the same speed. So it’s true, vibrations can absorb a huge amount of energy. It was almost impossible to keep the bike moving at our testing speed on the “very rough” road. (Of course, in real life, you don’t ride on rumble strips, but the point was to see how much energy could be lost just by changing the surface roughness, and keeping everything else the same.)

Since we were going at the same speed as on the smooth pavement, the our wind resistance was the same, and yet we had to push the pedals with 290 Watts more. So where did all the energy go?

A little bit went into heating the tire as it flexes, but pneumatic tires don’t absorb much energy even when they bounce. Think of a basketball. When you drop it, it bounces back almost as high as before. Very little energy is lost, even though it deflects as it hits the ground. As the basketball hits the ground, it compresses and becomes an air spring. Then it stops, before it starts accelerating upward again. The ‘spring’ in the ball returns most of the energy, and the ball bounces almost as high as it did with the last bounce.

Tires work the same way. When a tire hits a bump (left), it deforms (arrow). Energy is stored – the tire becomes a compressed spring. On the other side of the bump (right), the energy is released, pushing the tire off the bump. The net loss of energy is small.

If the energy isn’t lost in the tire, then where does it go?

The answer is simple: As the rider’s body vibrates, the tissues (muscles, tendons, skin, etc.) rub against each other. This can convert an enormous amount of energy into heat. How much? In a study of vibrating tank seats, the U.S. Army found that up to 2000 Watt were absorbed by a human body before the vibrations became too painful to endure. The discomfort was directly proportional to the energy loss.

2000 Watt! That is more than the power output of a pro racer. Clearly, a lot of energy can be lost due to these vibrations. The technical term for this is “suspension loss”. It also occurs in shock absorbers of cars – rally cars’ shock absorbers absorb so much energy that they get hot – so hot that they need dedicated cooling.

We also tested different types of equipment on the new, super-smooth pavement next to the rumble strips. We were surprised that even on very smooth pavement, reducing vibrations through supple tires – and even, to a lesser degree, a suspension fork – resulted in significant performance gains.

What this means for cyclists is simple: If your bike’s vibrations are uncomfortable, it’s because energy is converted into heat, inside your body. This energy is lost from the forward motion of the bike. As far as vibrations are concerned, being uncomfortable slows you down. Or seen the other way around, the more comfortable your bike is, the less power goes to suspension losses, and the more power is available to drive it forward:

Comfort = Speed

It really is that simple. And it’s revolutionized how we think about bikes: Wide, supple tires are faster because they vibrate less. Fork blades that absorb road shocks – even suspension forks – are faster, not just on rough roads, but even on relatively smooth roads, because they reduce vibrations. On real roads and at the speeds most of us ride (<25 mph), the best gravel and all-road bikes actually are faster than their racing bike cousins.

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This means that the biggest improvement in your bike’s performance comes from a set of wide, supple tires. “Supple” means that the casing is thin and easy to flex. This has two benefits:

1. Supple tires are easy to flex, so they transmit fewer vibrations (lower suspension losses). That is Reason 1 why they are faster.
2. Supple tires are easy to flex, so it takes less energy as they deform them as they rotate (lower hysteretic losses in the tire casing itself). Reason 2 why they are faster.

Wide tires also transmit fewer vibrations, which makes them faster than narrower ones.
Our testing shows that supple casings are more important than width. A supple 26 mm tire is much faster (and more comfortable) than a stiff 38 mm “touring” tire. Of course, ideally, you’ll get it all – a wide and supple tire.

This research led us to develop our Rene Herse tires. While quite a few makers offered supple racing tires in widths up to 25 mm, there weren’t (and still aren’t) many great high-performance tires in wider widths.

For our Extralight series, we use a casing that usually is reserved for high-end, hand-made racing tubulars. On top goes a layer of extra-grippy, yet long-wearing, rubber with our trademark tread pattern that interlocks with the road surface for extra grip. The result are our Rene Herse tires – available in widths from 26 mm to 55 mm.

Before releasing these tires in 2014, we tested them extensively on some of the roughest gravel roads to ensure they were durable enough for real-world riding. Since then, they’ve proven themselves in gravel races, but also on paved courses like Paris-Brest-Paris. They even took second place in the Washington State Road Racing Championships. The riders who use them are our best advertisers, recommending them to everybody who is willing to listen. We rarely advertise – instead, we focus on new research that will improve our products even further.

Further reading:

• Bicycle Quarterly‘s research on tire performance and suspension losses.

Photo credit (gravel racing): Chyla’s Race Photos.

What is the ‘correct’ tire pressure for your bike? The simple answer is: Whatever feels right to you. Confused? Here is how it works:
In the past, many riders inflated their tires to the maximum pressure rating. Now most cyclists now recognize that the optimum pressure often is much lower.

But what is the right tire pressure? At Bicycle Quarterly, we’ve done a lot of research into the rolling resistance of tires at various pressures, and on various road surfaces.

Frank Berto’s tire pressure chart (above), first published in Bicycle Quarterly many years ago, has received much attention. (Note that the weights are per wheel, not for the entire bike.)

Berto made the chart in the 1990s, when tires were much narrower. Hardly anybody today still rides on 20 mm tires, and even 23 mm are on their way out! At the other end, 37 mm no longer is huge, as many of us ride 42 mm tires on pavement, and even wider ones on gravel. How does it all translate into the modern world?

Much of it depends on the tires you run. Berto measured the tire drop (above; how much the tire deflects for a given load and pressure) for dozens of tires. He then averaged the values, and drew his chart for a tire drop of 15%.

The 15% as desirable tire drop was based on the recommendations of several tire manufacturers, but not on actual testing. So the chart shows how much you need to inflate an average 1990s tire to achieve a tire drop of 15% – nothing less and nothing more.

A few years ago, Berto sent me all his original data. Looking over his measurements, it’s clear that supple tires – back then pretty much only the Michelin Hi-Lite – deflect much more than stiff ones, at the same pressure. This means that specific tires can vary quite a bit from the averages shown in the chart.

To get the same tire drop with supple tires, you would need to run them at higher pressures. But is 15% tire drop really what you want with supple tires?

The answer is “No.” The 15% tire drop is an arbitrary value. However, even if it’s only by coincidence, the values in Berto’s chart actually work quite well for Rene Herse tires. They’ll result in more than 15% tire drop, but that is OK: Comfort and speed are optimized. And that is what really matters.

The biggest surprise of all our testing (above) was this: For supple tires, pressure makes little difference in performance. We tested three Vittoria tires (Rubino, CX clincher, CX tubular; all 25 mm wide) and found that the supple CX models roll as fast at 70 psi as they do at 130 psi. (For the rest of the world, that is 5 bar and 9 bar.)

The reason is simple: Higher pressure decreases the energy required to flex the tire. Less energy is lost due to internal deformation (hysteresis). But higher pressure increases the losses due to the vibrations of bike and rider. More energy goes to suspension losses. The two effects cancel each other. Whether you pump up your supple tires super-hard or ride them squishy-soft, they have the same resistance.

On the other hand, truly stiff tires feel sluggish at 15% tire drop. The stiff tire is much harder to flex, so it’s useful to minimize that flex by increasing the pressure. For stiff tires, the suspension losses do not vary as much with pressure – they’re always high – since the stiff casing transmits a lot of vibration at any pressure.

Recently, Velo-News confirmed our results: The performance of a hand-made tire with cotton casing did not change at different tire pressures. And a stiffer tire rolled slower at lower pressures than at higher ones. (It’s nice to see that our results, after having been highly controversial for years, now are becoming generally accepted.)

It can be hard to believe this, because higher pressure feels faster. Here is why: When you go faster, your bike hits more road irregularities per second: The road buzz increases in frequency. Most cyclists know: higher speed = higher frequency.

Higher tire pressure cheats you into thinking that you are going faster, because it also increases the frequency of the vibrations: higher pressure = higher frequency.

It’s natural to assume that this means: higher pressure = higher frequency = higher speed, but that is incorrect. Instead, you are looking at two different mechanisms that both increase the frequency of the road buzz.

Even after years of riding supple, wide tires, this ‘placebo’ effect sometimes plays tricks on me. A supple tire absorbs vibrations better, so it can feel slower – until you look at your speedometer.

What does it all mean? Here is the take-home summary:

• Stiff casings always will be slow. They are even slower at lower pressures.
• Supple casings are fast, and pressure doesn’t matter.
• On smooth roads, tire pressure is a matter of personal preference (at least with supple tires). High and low pressures offer the same performance.
• On rough roads, lower pressures are faster. So if you want to optimize your speed on all roads, including rough ones, go with a relatively low, but safe, pressure.
• Your tire pressure needs to be high enough to avoid pinch flats. If you get pinch flats, increase your tire pressure, or better, choose wider tires. Pinch flats are rare with wide tires.
• On pavement, your pressure needs to be high enough that the tire does not collapse during hard cornering.
• The minimum safe pressure is higher for more supple casings. Stiff casings hold up the bike more, and thus require less air pressure.
• On gravel, you can run lower pressures than on pavement. On loose surfaces, the tires don’t collapse as easily, because the cornering forces are much lower.
• Don’t run your tires so low that the casing cords start to break. That happens only at very low pressures, but if you start seeing multiple lines across the casing where cords have broken, inflate the tires a bit more.
• Berto’s chart still is a good starting point. Inflate your tires to the pressures it recommends, then experiment by adding or letting out some air.
• See what feels best to you. That is the optimum tire pressure for you. Don’t worry about tire pressure any further! At least on paved roads, you won’t go faster or slower if you change your tire pressure.

Even simpler, here is a summary in two sentences:

• Ride the tire pressure that feels good to you.
• When in doubt, let out some air.

It’s really that simple!

Further reading:

• Minimum tire pressure: How low can you go?
• What makes a tire supple? (It’s not TPI alone.)
• Bicycle Quarterly magazine

As a child, I used to think of Japan as a densely populated place full of skyscrapers and freeways. Of course, those big cities exist, but much of Japan is very rural. So when I travel from Tokyo to visit the Panaracer factory, I get to experience that transition from city to countryside.

My trip starts with one of the incredible Shinkansen trains. These trains now travel at up to 320 km/h (200 mph). Their shapes are designed to reduce turbulence when two of these projectiles meet at full speed in a tunnel. (Imagine the pressure wave!)

On the way, the train speeds by Mount Fuji, and I am reminded why the Japanese revere this volcano so much. It really is stunning.

In less than 2 hours, I am in Osaka, more than 500 km (310 miles) from Tokyo. But my trip is far from over. I now switch to the standard narrow-gauge Japanese railways, and board the “Kounotori Super Express” (above).

By American standards, it’s a fast train, and the trip through gorges and tunnels is spectacular. After 1.5 hours, I have crossed an entire mountain range, but my trip isn’t over yet.

I now change to a local train, the kind that is used by schoolchildren and people going shopping in the next town. This train finally takes me to the small town where the Panaracer factory is located. From the station, it’s just as brief walk to the place where our Compass tires are made.

What inspired our tires is also what the workers see when they look out of the factory gate: mountains.

It’s always a privilege to meet Panaracer’s engineers (above). We present them with our ideas, they give us their feedback, and we discuss how we can further improve our tires. We discuss rubber compounds, casing materials, tread patterns, and other things that make our tires perform as well as they do.

Several Panaracer engineers are avid riders themselves. All are as passionate about bicycle tires as we are, and I enjoy working with them immensely. And best of all, I get to enjoy the tires’ performance in the mountains that have inspired them.

Recently, I posted about slick tires and why they tend to offer poor traction, especially in the wet. Almost predictably, some Internet “experts” declared that it was all wrong. One of the more polite comments was: “Wow, lots of misinformation in this article.”
I guess it’s normal: If your research is breaking new ground, the results aren’t what people think they know. But the unexpected isn’t always wrong.
What the “experts” really are saying is: “This isn’t what most people believe right now. It may take a few years until it becomes widely accepted.”

The same thing happened when we first published Bicycle Quarterly’s real-road tire tests a little over eight years ago. Back then, the idea that higher tire pressures do not increase speed bordered on heresy.
The idea that tires roll faster the harder you pump them up seemed so evident that there wasn’t even a need to discuss this. Every tire company expert agreed with this. End of story. Or so it seemed.

We were just as surprised by our results as everybody else. But after double- and triple-checking the results by running more tests, we concluded that the results were real.
Bicycle Quarterly has two people with Ph.D.’s on our editorial team, so we know how to design experiments, test hypotheses, and do statistical analyses to ensure that we are measuring real differences between tires and not just variations in the testing conditions. (The last point is very important, yet it’s often omitted in cycling research.)
How to explain these new findings? We realized that the “accepted wisdom” overlooked an important factor: Suspension losses caused by the vibrations of bike and rider consume significant energy. With higher tire pressure, suspension losses go up, and they cancel out any reduction in rolling resistance that comes from less internal deformation of the tire.
Previous testing had been done on smooth drums, were suspension losses don’t occur. That is why the experts missed a crucial part of the equation, and their conclusions did not match the real-road testing.

Test results are fine and well, but the results must confirmed on the road. Apart from BQ staff and readers, professional racers were the first to adopt our idea of running wider tires at lower pressures. On the cobbles of Paris-Roubaix, you now find many pros running 30 mm-wide tubulars at 70 psi. The days when racers used suspension forks and narrow tires pumped to high pressures (above) are long past.
And even on the smooth roads of the Tour de France, the pros run 25 mm-wide tires, which is a huge step up from the 21.5 mm tires that were standard when I last raced on the road 15 years ago. In fact, I am envious that today’s racers have 35% more air volume in their tires than I did!

And finally, even the “experts” have come around. It was gratifying to read a decent explanation of suspension losses in Lennard Zinn’s recent Velo tire test:
“If you were riding on smooth glass, higher pressure would be better. On rough surfaces, however, a tire at lower pressure is better able to absorb bumps, rather than deflecting the entire bike and rider upward.[…] The less energy is sent upward with each bump, the less energy it takes to keep the bike rolling.” 
Even though most Internet experts now accept our tire pressure research, they aren’t any more open to new ideas than they were eight years ago. I read that tire tread is purely cosmetic, because tires don’t hydroplane. (True, but tire tread isn’t there to displace water.)  That slick tires stick better, because they put more rubber on the road. Various tire experts were quoted.
Could it be that the experts once again are overlooking something? Back in 2007, they didn’t realize that suspension losses were important.
Perhaps now the idea that the bicycle tire tread can interlock with road surface irregularities is still a little “out there” – even though it’s long been known and accepted by many tire experts. (I first read about it in a 1980s paper authored by a Michelin tire engineer.) Perhaps we have to wait another eight years until the idea is generally accepted…

In the mean time, we’ll continue to do what we always do: ride our bikes. And we already know that the new Compass tires offer excellent traction, both on dry and wet roads. Everybody who has ridden them seems to agree. To me, that is all that matters. Because when it comes down to it, I’d rather be riding than discussing bikes online.

In our last post, readers noticed the image above and asked about cornering. How am I able to lean the bike so far?
Wider bicycle tires corner better than narrower ones. This may run counter to what many cyclists believe, but it’s easy to explain. The reason is the lower pressure at which you can run wider tires without risking pinch-flats. This has two effects:
1. Wider tires run at lower pressures and thus have a larger contact patch. This simply puts more rubber on the road and increases cornering grip. While simple physical theory suggests that friction should be independent of tire width – narrower tires are pushed onto the road with more pressure – in practice, wider tires provide more interlocking surfaces between road and tire, and thus provide more grip. If you don’t believe this – after all racing bikes use relatively narrow tires – look at racecars or racing motorcycles.
2. Wider tires absorb bumps better. This keeps the wheels on the road and provides more consistent adhesion. A narrow, high-pressure tire skips over the surface, which limits its grip. Even the smoothest asphalt is surprisingly rough. That is why race cars and racing motorbikes have suspension, and why they run their tires at 35-40 psi. If you inflate your tires to 90 psi or more, you are giving up a lot of cornering adhesion. (For the same reason, tires with stiff sidewalls don’t corner as well, because they don’t absorb the vibrations and bumps like tires with supple sidewalls.)

So much for the theory – how does it translate into the real world? A few years ago, we tested two titanium racing bikes against a 650B randonneur bike. We raced two bikes side-by-side up a steep hill (above), then turned around and rode back down the twisty descent.
I have talked about the uphill part of this test elsewhere, but the downhill part was equally surprising: In the corners, the racing bike with its 25 mm tires could not keep up with the randonneur bike on its 42 mm tires. The riders changed bikes, but it was always the randonneur bike that went down the hill faster. There were two corners, one extra-smooth with new pavement, the other bumpy. The wider tires were better in both corners. Not surprisingly, the advantage was magnified in the bumpy corner. And since the randonneur bike exited the corner faster, it also went faster on the straight that followed.
How did it feel riding the racing bike? I was one of the riders, and I consider myself a good descender, so I wasn’t happy when second tester Mark distanced me while he was on the randonneur bike. While I was riding the racing bike, I had to try hard to keep up. The first, smooth corner felt a bit unsettled, but then I really frightened myself in the second corner. I picked a good line that avoided the bumps, but my front wheel started skipping across the surface. I had to open the radius of my corner and went about a foot into the oncoming lane at the corner exit. In the same spot, the randonneur bike’s wide front tire simply keyed into the surface and rounded the corner without drama. (Both bikes were equipped with Compass tires, so the tread compound was the same.)

Of course, you can’t just slap wider tires onto any bike and expect it to corner like a machine custom-designed to optimize the handling. Here are some of the issues:

• A wider tire’s larger contact patch stabilizes the bike. (This is called pneumatic trail.) If your bike’s geometry isn’t designed for wide tires, then your bike can feel sluggish in its response to steering inputs when you increase the tire size.
  Solution: Decrease the geometric trail to account for the pneumatic trail of the tires.
• Wider tires tend to be a bit heavier, and thus have more rotational inertia. This makes the bike more reluctant to turn into a corner, or to change its line in mid-corner.
  Solution: Reduce the wheel size as the tire gets wider, to keep the rotational inertia within the range that gives the best handling.
• Wide tires run at low pressures, but too low pressures can allow the tire sidewall to collapse under the cornering forces, which is not good at all.
  Solution: Make sure your tires are inflated enough to prevent sidewall collapse even under hard cornering. Especially supple tires don’t have much sidewall stiffness, and need a little more air pressure to hold them up.

Beyond that, technique can help. On bikes that are too stable because their tires are wider than is optimal, you may need to actively countersteer (that is, push the handlebars to the outside of the curve) to get the bike to lean. On optimized bikes, you do that, too, but you never notice it because the amount of countersteer is totally intuitive.
Overall, there is little doubt that wider tires corner better, all things being equal.
Further reading:

• Balancing and Cornering on a Bicycle: Bicycle Quarterly 34 (Winter 2010)
• Countersteering: Bicycle Quarterly 50 (Winter 2014)
• Tire Tread — What Does it Do? Bicycle Quarterly 43 (Spring 2013)
• Wheel Size and Bicycle Handling: Bicycle Quarterly 31 (Spring 2010)
• Gyroscopic Forces and Optimum Wheel Sizes:Bicycle Quarterly 31 (Spring 2010)

Our very first Enduro Allroad prototype tires started out as knobbies with supple casings – then we had the knobs shaved off by Peter Weigle. We wanted to test the concept of a very wide, supple tire before committing to expensive tire molds. We were happy to report that the tires performed even better than expected! So we decided to proceed.
Last week, the project reached another milestone: We received prototypes made from the actual production molds. So while these are made as a very small batch and required even more hand-work than the final tires, they are basically the tires that you will be able to buy and ride in a few months.

The first samples we received were the 26″ x 54 mm tire. (For some reason the tire mold was changed to 58 mm after we approved the text!) This batch uses the “standard” (supple) casing. When we put one of the tires on the scale, it weighed 454 grams – quite light for a tire this wide.

Mounted on a 23 mm-wide rim, the tire measured a little over 49 mm. In the two days since, the tire has “grown” by 2 mm. The “Extralight” tires tend to stretch even more, so when used with wider rims, they’ll probably be close to the anticipated 54 mm.

Then we received a second box… This time, it contained the 650B x 48 mm tires – made with the extra-supple “Extralight” casing. Out came the scale again, and we measured 413 grams – remarkable for such a big, puffy tire.

Mounted on a 23 mm-wide rim, this tire measured just over 48 mm right away, and like the 26″ tire, it has grown 2 mm in the days since we mounted it. That means that this tire is slightly wider than planned. Its width is just a millimeter or two narrower than the 26″ tire.

Of course, measurements don’t tell us much about the tires: What we really want to know is how they ride. Fortunately, our friend Alex Wetmore has two bikes with similar front-end geometries (both have 40 mm trail). One is his “normal” bike, set up for 650B tires (above). The other is his “Travel Gifford”, which runs 26″ tires (photo at the top of the post). These two bikes are perfect candidates to compare the new tires.
Aired up to about 28 psi, I took to the streets and trails in Seattle’s Ravenna neighborhood. On the broken pavement of the residential streets, I wondered why we don’t ride these tires all the time. Even the 42 mm Babyshoe Pass tires of my Urban Bike, which I had ridden to Alex’ house, were surpassed for comfort and secure handling by these even bigger tires.
Riding the two bikes back-to-back, the differences due to the different wheel sizes were very noticeable. The 26″ bike felt very nimble and agile. It was easy to pick a line, but the handlebars required a light touch to maintain that line. The 650B bike, with its larger wheels and greater rotational inertia, felt much more stable. It required more input to change its line, and catching a slide on gravel took a hair longer than it had on the 26″ bike. The 650B bike also had an (empty) front rack, which further stabilizes the steering. While the steering of the unloaded 26″ bike was a tad light, adding a rack and handlebar bag would make it more stable. Both bikes handled fine, they were just at the opposite ends of what I consider “fine handling”.
The real revelation came on gravel. Both bikes felt like good road bikes. The uphill traction was amazing. Sprinting out of the saddle was easy. Only the cornering speeds were lower than on pavement – when the gravel starts sliding under your wheels, no tire can maintain traction. These tires really are a revelation – they have changed how I think a bike can perform on gravel.
Production of the new tires is scheduled, and we hope to have them in stock by July or August. Click here for more information about Compass’ existing tire program.

Last year’s Oregon Outback was a great test for the ultimate gravel bike. The course consisted of 1/3 rough and soft gravel, 1/3 smooth gravel and 1/3 pavement. The situation is similar to our favorite local rides: We leave from our backdoor on pavement and ride up to the mountains, where we explore gravel passes far off the beaten path.
What is the ideal bike for this type of riding? We approached the subject by evaluating the real-world performance of different bikes, without regard to tradition and established practice. As we reported in more detail in the Spring 2015 Bicycle Quarterly, we found:

• Road bikes are faster than other categories (mountain bikes, fat bikes, etc.).
• The widest tires that can fit between the chainstays of a road bike measure about 52-54 mm. Any wider, and you have to use mountain bike cranks with wider tread/Q factor.
• Using 26″ rims keeps the outer diameter of the wheel similar to a 42 mm-wide 650B wheel. This makes it possible to use short chainstays, and it also maintains the nimble handling we enjoy in our bikes.
• Our testing has shown that the small differences in wheel size between 26″, 650B and 29″/700C don’t affect how well a tire rolls over moderately bumpy terrain.

With one question remaining:

• We’ve already seen that supple casings are faster and more comfortable, but what happens if we make a supple tire that is 50+ mm wide? Nobody had ridden supple tires that wide on the road, simply because no such tires have been available.

There was only one way to find out: Make some prototype tires! Thanks to our cooperative effort with Panaracer (who made a few sets of knobbies with the Compass Extralight casing) and Peter Weigle (who then shaved off the knobs), we were able to get prototype tires with the extra-supple casings, but in a 26″ x 2.3″ size (above). Then we went out to test them, using Alex Wetmore’s “Travel Gifford”, a road bike that is designed for wide 26″ tires (below).

What did we find out? Off-pavement, the wider tires are absolutely amazing. Perhaps that is not surprising, since the tires hold 70% more air than a 650B x 42 mm tire! On these 51 mm-wide prototype tires, the bike simply floats over rough gravel, yet the sensations are those of riding a road bike on pavement. With the low tire pressure and supple casing, traction is amazing. Sprinting up hills out of the saddle is easy, where bikes with narrower tires simply spin their rear wheel. Now I understand why many professional mountain bike racers ride on FMB or Dugast tubulars.

The biggest question for us was how the new tires would perform on the road. After all, tires are big air springs, and the more supple the casing, the less damping you get. Would the bike bounce down the road like a basketball?
We are glad to report that this isn’t the case. If the tire pressure is too high, the bike gets a little unsettled on undulating pavement. The window between “too high” and “too low” pressure is smaller than on narrower tires. In that sweet spot, the bike rides and corners like a road bike, except with much, much more grip on dry roads. The contact patch is huge, and more rubber on the road results in more traction. The lower tire pressure means the wheel doesn’t skip over surface irregularities, so it never loses traction. It’s amazing how far you can lean over on these tires without even getting close to the limits of tire adhesion. (That is why racecars have extremely wide tires.)
What about rolling resistance? We have not done any carefully controlled tests yet, but our on-the-road experience indicates that it’s no higher than narrower tires. Whoever rode the Enduro Allroad Bike during our testing easily kept up with the rest of the group.
So what are the drawbacks? Well, there are a few:

• You can use these tires on most mountain bike frames, but if you want to use “road” cranks with narrow tread (Q factor), your frame needs to be carefully designed and built to fit the ultra-wide tires.
• Fenders will not be able to wrap around the tire as they do on bikes with narrower tires, since you cannot make the fenders much wider than 60 mm while keeping a “road” chainline. (The chain would hit the fender in the smaller gears.) The solution probably is to use a 60 mm-wide fender with a shallow profile and mount it a little higher above the tire.
• As noted earlier, the tire pressure needs to be maintained more carefully.
• Since the tires are so soft, the bike tends to get deflected by longitudinal depressions in the pavement a little more than bikes with narrower tires.
• It appears that the bike is more likely to shimmy with tires that wide.

For bikes that see mostly pavement use, with only occasional forays onto gravel, 650B x 42 mm tires will remain my preferred option. But I know I’ll add an Enduro Allroad Bike to my stable for those rides where we spend significant time on gravel.

What about the name “Enduro Allroad Bike”? We wanted to emphasize that it’s a road bike, not a mountain bike. Yet it’s not limited by its narrow tires like a typical road bike. We already use “Allroad” for our 650B bikes. To emphasize the “go-anywhere” capabilities, we added “Enduro”. A road bike that can go on any road and beyond…
For those of us who would prefer to float over gravel rather than “grind” through it, the Enduro Allroad Bike is an exciting new development. Compass Bicycles will offer the Rat Trap Pass, a 26″ x 2.3″ (54 mm) tire specifically designed for this type of bike. Rawland is working on their Ravn, the first production Enduro Allroad Bike that is designed around this tire. MAP also is considering making a small production run of Enduro Allroad Bikes. Of course, custom builders can make them, too. And other companies will probably offer them as well, since they make so much sense and are so much fun to ride.
If you want to try supple, ultra-wide tires but still prefer to stick with 650B wheels that you may already have, Compass will offer the Switchback Hill, a 650B x 48 mm tire. There are many 650B bikes that can fit a tire that wide, and you’ll get 30% more air volume than a 42 mm tire offers. Both new tires will be available this summer.

Over the last decade-and-a-half, I’ve thought a lot about product development. Long before Bicycle Quarterly and Compass Bicycles, I was involved with several companies as a technical writer and translator. Part of my job was writing instructions, so I got to see product development up close.
From my experience, product development ideally has three components:

1. Skilled users who are sensitive enough to report what they experience.
2. Scientists who design tests to confirm those observations and isolate the factors involved.
3. Engineers who translate those findings into better products.

With Bicycle Quarterly, it didn’t take long until we got involved in No. 1. We rode many bikes over challenging courses, and we noticed differences in how they performed, how they handled, and how they felt.
From those observations, it was a small step to No. 2. After all, our editorial team is made up of scientists, so the question “Why do some bikes ride/perform/handle better than others?” came up quickly. We began testing tires, we tested our hypotheses about frame stiffness, and we rode different front-end geometries.
No. 3 was a logical next step – what good are scientific findings if they don’t lead to bicycles people can ride? So we started Compass Bicycles to translate the results of our research into better bicycle components.

Sometimes, steps 1 and 2 are reversed. That is how our tires came about. I hadn’t thought much about tires, until I saw a tire test in the German magazine TOUR. (By the way, the title in the photo above translates to “Roll Well”.)
Among other things, TOUR tested the tires’ rolling resistance. They found significant differences, but downplayed them by saying that the difference would “only” amount to 138 seconds in a 40 km time trial. That got me thinking: First of all, more than 2 minutes in a time trial is a huge difference. When I raced, 10 seconds over 10 km made the difference between first and fifth place. Could the faster tires have made me a consistent winner? More importantly, speeds are lower for the long rides we now enjoy, so rolling resistance is even more important.
Talking with Mark Vande Kamp (friend, riding companion and fellow Ph.D. on Bicycle Quarterly‘s editorial board), we decided to see whether we could replicate TOUR‘s results, but at lower speeds. We bought a set each of the fastest tire in the TOUR test, as well as a slower one. We scouted a location for a rolldown test, and one Saturday morning, we installed the test tires on our bikes and headed to the hill. I rolled downhill, first on one tire, then on the other (always using the same bike, of course). Mark timed me and found that the differences were quite large: about 10% faster with one tire than the other. We repeated the experiment, and the results were the same. Wow! Tires did make a larger difference than we thought. We knew we had to test this further.
We then went on a long ride and discussed what we wanted to test. Different tire models, obviously, but also different pressures. After all, we always were torn between inflating our tires to the maximum pressure to obtain the highest speed, and reducing the pressure a little to improve comfort. How much speed did we lose if we went for comfort? We also decided to test the same tires in different widths. And worn tires against new ones, to determine how much of a difference tread thickness makes. (Worn tires have a thinner tread, but otherwise are the same as new ones.)

The testing took a lot of time and effort, but the results were worth everything we put into it. We found out that the tires I had been using were among the slowest tires in our test. Simply replacing my tires allowed me to stay with previously faster riders during brevets. And when I rode alone, I consistently set personal bests, despite my training being the same as before.
As a positive side effect, the faster tires also were more comfortable. However, comfort was relative: The fastest tires in our test were only 24 mm wide – too narrow for true comfort on backroads.
Our research showed ways to improve these tires. We found that tire pressure did not have a significant effect on speed. This opened up a whole new way forward for tire design. Instead of trying to make wider tires withstand high pressures (which requires strong, stiff casings), wider tires should be made supple casings. Despite running at lower pressures, they’d be much faster.

At the time of our tire tests, we just had started to sell the first-generation Grand Bois tires (above). We were disappointed that they did not score well in our tests. We shared our results with Grand Bois and Panaracer, and they came up with an improved version that had a more supple casing. That was the first product that came directly out of Bicycle Quarterly‘s testing.
Over the next few years, the Grand Bois tire program expanded, and we were able to test our findings on the road. We found that even with 42 mm-wide tires, our bikes were no slower than bikes with narrower tires.

We felt that further improvements were possible by optimizing the tire tread for performance. The tread on the shoulders of the tire only contacts the road during hard cornering, so it doesn’t wear out. We could make this thinner, so the tires would be even more supple and faster. We tested many tread patterns to obtain an optimum of cornering traction both on dry and wet roads. The result were our Compass tires. Our customers rave about their comfort, speed, cornering grip…
Our tires are just one example of the symbiotic relationship between Bicycle Quarterly and Compass Bicycles. Without Bicycle Quarterly‘s research, we wouldn’t have known that the tires we were using were slow. And without Compass Bicycles, our research would have remained of little use to riders. We would have outlined “ideal” performance tires, but without anybody making them, that knowledge would not have improved our riding experience.

The main reason Compass components exist is so we can use them on our own bikes! And I truly believe that our riding experience has improved in many ways since we starting riding on wide, supple tires.
Click here to learn more about Compass tires.

A little while ago, I wrote about how new scientific research has allowed us to design wide, supple tires that offer the speed of narrow, high-end racing tires. The key finding is that above a certain threshold, increasing tire pressure no longer results in lower rolling resistance. While these new data have become widely accepted – witness professional racers adopting wider tires and lower pressures – it’s natural that new ideas are met with skepticism. In order to contribute to a better understanding of how tires work, I’d like to share more data from Bicycle Quarterly‘s testing.

The data above came from Bicycle Quarterly rolldown tests of various tires. The results indicate that above a certain threshold, for clinchers, tire performance increases only very slightly, if at all. It’s not surprising that the 38 mm-wide Mitsuboshi tire rolled faster at 35 psi than at 25 psi – it was hardly rideable at the lower pressure. But increasing pressure to 55 psi resulted in no speed increase.
We saw the same for the 27 mm-wide Rolly-Poly. Somewhere between 55 and 85 psi, higher pressure no longer resulted in significantly increased performance. Going from 85 to 105 psi resulted in only a minimal increase in speed. For the two tubular tires, the effect was reversed: Higher pressures actually reduced performance.

We’ve confirmed this finding numerous times. Above is another set of test runs (pressures are in bar/psi). For these 32 mm tires, increasing the pressure from 7o psi to 85 psi brought no significant change in performance. (The apparently slower speed at 85 psi is not statistically significant.) Please note that the values you see here are not corrected for temperature, so you can’t compare different tires. (The pressure runs were done consecutively, so temperature didn’t change from one pressure to the next.)

We discussed the measurements with power meters in the previous post (above). That data also has been confirmed multiple times, at different speeds.

Above is data from running ultra-high pressures, up to 200 psi. Performance did not change with increasing pressures. (Don’t do this at home, 14 bar/200 psi is not safe with these tires!) I could bore you with even more data, but I think this is pretty convincing, especially since we’ve confirmed numerous times that our tests are repeatable (testing the same setup multiple times yields the same results) and statistically significant (meaning we aren’t just looking at random noise in the data). That is important, because all too many studies are based on single test runs, which don’t meet basic scientific requirements. Now that we’ve conclusively debunked the old view of “higher pressure = more speed”, let’s look at some of the details in the data above.
Rough vs. Smooth Pavement
The rolldown tests were performed on relatively rough pavement. No holes or bumps, but the tar between the aggregate had washed away over decades of Seattle weather. Interestingly, high pressures generally did result in slightly higher speeds for some clincher tires. It’s not a lot, but it’s statistically significant.
The track tests were run on very smooth, newly laid asphalt pavement. There, we see the opposite. High pressures of 100-110 psi result in slightly lower speeds. How can we explain this? One hypothesis is that the tire deforms more on the rougher pavement to conform to the surface irregularities. At lower pressure, you create an imprint of the road surface in the tire as it rolls. At higher pressure, the tire bridges the gaps between the high points, and thus deforms less. On the smooth road, there aren’t any gaps to bridge, and so the high pressure loses its advantage.
Moderately high pressure = worst performance
On the smooth track, moderately-high pressure (100-110 psi) is worse than either lower or higher pressures. Why is that? Here is a possible explanation: As you increase the pressure, the suspension losses (vibrations) increase faster than the flexing of the tire (hysteresis) is reduced. So you lose performance as you increase pressure. At a certain point, the bike is vibrating as much as it can, but higher pressures still reduce the flexing of the tire. So from that point onward, higher pressures improve performance – until you end up back where you started at lower pressures.
Tubulars vs. Clinchers
What about the worse performance of tubulars at higher pressures? Tubulars derive much of their performance from their suppleness and low suspension losses. Increasing the pressure increases vibrations faster than it reduces the flexing of the tires. These explanations are just hypotheses – our best guesses to explain what we see. The data itself – higher pressures don’t lead to improved performance – is beyond doubt.

Take-Home Message
For most riders, the take-home message is simply this: As long as you inflate your tires enough that they are safe to ride, tire pressure doesn’t matter much. Find a pressure that feels good when cornering, and ride your tires at that pressure. When in doubt, let out some air – you’ll be more comfortable and have better cornering grip. (If you ride narrow tires, beware of pinch flats, though!)
If you worry about the last bit of performance, then you can try to use the data above to tease out that last 2%. On smooth roads, low tire pressures yield the best performance. On rough pavement that doesn’t have holes or bumps, increasing your pressure may make your tires a little bit faster. That may seem counter-intuitive, and of course, it also will be less comfortable. But if you are doing a short time trial on a country road, it may be worth considering. Ideally, you’d run a few experiments with a power meter to dial in your tire pressure for that particular road surface.
If you run tubular tires, you should definitely run them at relatively low pressures. This provides the best performance and the best comfort on all surfaces we’ve tested. As for me, I run my tires at relatively low pressures on all roads. My rides encompass a multitude of surfaces, and on truly bumpy roads, we’ve shown that lower pressures always are faster, because the bike bounces less. But that is a topic for another day…

• Further reading:
• What are suspension losses?
• The Performance of Tires: Bicycle Quarterly Vol. 11, No. 4.
• Roll-down tests of tire performance: Bicycle Quarterly Vol. 5, No. 1.
• More roll-down tests of tire performance: Bicycle Quarterly Vol. 5, No. 3.

Of all our research on tires, the most revolutionary finding is this: Tire pressure has almost no effect on a tire’s speed. We did not believe it at first, either, so we’ve tested it numerous times. It’s been confirmed numerous times, with different methodologies.
The real revolution is not how you use your pump… What has totally changed our riding are the wide, supple tires, which only work because of this new insight.

First, let’s look at the data. Here is one experiment: We ran three different 25 mm tires (a supple clincher, a supple tubular and a harsher-riding clincher) at pressures from 4.5 and 9 bar (65 and 130 psi). These tests were done on very smooth asphalt (above), a surface where high pressures should offer the greatest advantages. The graphs below show the power required to ride the bike (above) with the tires at a constant speed of 27.8 km/h, but with different tire pressures.

There is no relationship between tire pressure and performance in the tested range. (Lower and higher pressures are unsafe to ride.) The graph above shows some variation in power output (lower is better), but there is no trend. The CX tubular rolls fastest at 5.5 bar, the CX clincher is a little faster at 6 bar, while the Rubino is fastest at 9 bar, but almost as fast at 6.5 bar.
Take-home message: Don’t stress about tire pressure!

This finding has revolutionized our understanding of tires. In the past, we all thought that higher tire pressures made tires roll faster. And that presented a problem for wide tires: A wider tire puts greater loads on the casing than a narrow one. To compensate, you have two choices:

1. Beef up the casing, which makes the tire less supple and slower.
2. Lower the pressure, which we thought made the tire slower.

No matter which route you took, then-available science predicted that your wider tire would be slower. It was a catch-22, and for the best performance, you stuck with narrow tires, where you could have a supple casing and high pressure at the same time.
But after realizing that tire pressure doesn’t matter for performance, we were able to explore new possibilities. If lowering the pressure does not make tires slower, you can make supple, wide tires. You run them at lower pressures, and you don’t give up any performance on smooth roads. On rough roads, you gain speed, because the tire (and you) bounce less. And on all roads, you are more comfortable. Instead of a catch-22, you have a win-win-win situation.

It’s this research that has led professional racers to adopt wider tires. They are up to 25 mm now. (Wider ones won’t fit on their bikes!) For the rest of us, there is no reason not to go wider. I now ride 42 mm tires at 3 bar (43 psi), knowing that they roll as fast as a 25 mm tire at 6 bar (85 psi) – or 9 bar (130 psi), for that matter.

To get the most benefit out of these lower pressures, you need supple tires. A stiff sidewall takes more energy to flex, so the tire will be slower. And since the sidewall is stiffer, it also will be less comfortable. You could call it a “lose-lose” situation.
Professional racers have known this all along: As much as their equipment has changed over time, they’ve always ridden supple tires. They usually ride hand-made tubulars (above), but for the rest of us, supple, wide clincher tires now make it possible to enjoy the ride and speed of supple tires on any road.

• Further reading:
• More data and details on tire pressure.
• The Performance of Tires: Bicycle Quarterly Vol. 11, No. 4.
• Roll-down tests of tire performance: Bicycle Quarterly Vol. 5, No. 1.
• More roll-down tests of tire performance: Bicycle Quarterly Vol. 5, No. 3.

Improving your tires can make the biggest impact in the speed of your bike (apart from changing the motor!). The difference is especially pronounced for slower riders, whose wind resistance is less than that of faster riders.
Most cyclists know that supple tires make you faster on your bike. But so do ceramic bearings in your derailleur pulleys. The important question is: “How much faster?” For ceramic bearings, the difference is too small to notice on the road, because standard ball bearings already have close to zero resistance.
For supple tires, the difference is much greater. If you have a hard time staying with a group, changing your tires to a faster model may help you avoid getting dropped. And if you get close to the time limit in brevets, faster tires can provide you with a significant time cushion, so that a flat tire or a slight detour due to misreading the route sheet no longer results in a DNF.
Here is a comparison between three tires from Bicycle Quarterly‘s tire tests. These are all marketed as performance tires, and none of them have puncture-proof layers that would further slow them down.

• Vittoria Open CX Corsa 700C x 25 mm
• Grand Bois Cyprès (standard casing) 700C x 32 mm
• Rivendell Rolly-Poly 700C x 27 mm

Our first tests were rolldown tests on relatively rough pavement, like you typically find on American backroads. The speed was between 23 and 25 km/h (13.5 – 15.5 mph).
On this surface, the fastest tire rolls 13.5% faster than the slowest. That is a huge difference. Imagine going 15 mph with the slower tire, and on your next ride, after changing your tires, riding at 17 mph with the same effort. During a century ride, you’d be 45 minutes faster!

We also tested these (and many other) tires on a very smooth asphalt surface at constant speed with a Power Meter. The speed was higher (27.9 km/h; 17.3 mph), and the ultra-smooth surface reduced the vibrations. However, even under these “ideal” conditions, the rider on the slowest tire had to put out 13.5% more power to keep up with the rider on the fastest tire. That can make the difference between “hanging with a group” and getting dropped within a few miles.
If you calculate the speed difference for the same power output, it’s 5%. (Wind resistance going up exponentially with speed, so you need 13.5% more power to increase your speed by 5% to stay with the rider on the faster tires.)
As you can see, supple tires make the greatest difference on rougher surfaces, and at lower speeds. But even at high speeds, make the largest difference in the performance of your bike. For comparison, aero wheels make you about 1% faster. And when you are drafting, your wind resistance goes down, so rolling resistance becomes even more important. That is why the pros always have ridden supple tires.
Does this mean we all should ride Vittoria CX tires? Not exactly. The CX is optimized for ultimate performance, and it has a very thin tread. This means it will wear out quickly and suffer more punctures on the way. If you are racing or riding a timed event, these compromises may be worth making. For everyday use, it often makes sense to give up some speed to obtain twice as much service life and fewer punctures.
The Grand Bois Cyprès is designed as an all-round tire. It has a thicker tread that will last thousands of miles. It will get faster as it wears. The Grand Bois also has a sturdier casing that resists sidewall cuts better. As a result, it rolls a little slower. (Disclosure: Compass Bicycles sells Grand Bois tires.)
The Rivendell Rolly-Poly has an ultra-tough casing that provides peace of mind when you ride through debris and are afraid of cutting your tire’s sidewalls. This may be overkill for most riders. The more rigid casing slows the tire down significantly.

When we designed our Compass tires, we started with the Grand Bois tires, and then optimized the performance further, without making the tires into “event” tires that are not very suitable for everyday riding. We reduced the tread thickness on the shoulders of the tire, where it does not wear out, but kept it the same in the middle, where it wears.
For the Extralight models, we used a casing that is significantly more supple than the “standard” casing shown in the test results above. We haven’t measured the performance under controlled conditions yet, but our (and others’) on-the-road experience suggests that they are significantly faster than the standard models.
Tires really make a big difference. When I switched from tires with stiff sidewalls to supple ones, not only did I set many personal bests on long rides, but I also found that I could rest while drafting, whereas before, I was working hard just to hang on.
Take our Flèche team in the photo at the top: If one of us had significantly slower tires than the others, he would have to be much stronger just to keep up. We’d rather have the stronger rider take longer pulls at the front!

What if you don’t care about speed? Supple tires also are much more comfortable. And they just feel different, making cycling much more fun. To me, that is the most important difference, and why I ride them on all my bikes.
Further reading:

• Click here to find out more about Compass and Grand Bois tires.
• Bicycle Quarterly tire tests: Vol. 5, No. 2; Vol. 11, No. 3; Vol. 12, No. 3.

How wide a tire is too wide for optimum performance? Our research shows that wider tires don’t give up anything on smooth roads, and gain a significant advantage on rough roads. This has been shown for tires up to 31 mm wide.
It’s now a well-established fact that wider tires roll faster than narrow ones. Professional racers now use 25 mm tires, which are 20% wider than the tires that most racers used just 20 years ago. Will this trend continue? Can we expect racers to be on 30 mm tires in the future? No matter what the pros do – they are influenced by many factors that have little to do with science – the real question is: Up to what point are wider tires faster?

It is obvious that the tires in the photo above will not roll very fast. Clearly, at some point, the performance benefits of wider tires (shorter contact patch and thus smaller hysteretic losses; reduced suspension losses) will be outweighed by the disadvantages of extra weight and increased wind resistance.

In our original tire tests (above), we tested the same tires in 21, 23 and 25 mm widths on a moderately rough “backroad” surface. The results were clear: The 21 mm tires were slowest, 23 mm was in the middle, and 25 mm tires were fastest. The speed difference between 21 and 25 mm tires amounted to about 2.5%. Over a typical 200 km brevet, I would gain about 11 minutes. It’s not huge, but significant. These results appear to have prompted the current trend of racers using wider tires.
What about tires that are wider than 25 mm?

Our testing on rumble strips showed that on very rough surfaces (the equivalent of cobblestones), 42 mm tires are faster than 25 mm tires. However, few of us ride all the time on cobblestones, and what we want to know is whether we give up anything on smooth roads when riding wider tires.
To determine this, we tested Grand Bois tires in 26, 29 and 31 mm widths on a super-smooth asphalt surface (see photo at the top of the post). The results were the same for all three tires. On the smoothest asphalt, you don’t gain anything by going to tires wider than 25 mm, but you also don’t give up anything.
Those tests were run at 25 km/h (16 mph). At higher speeds, the aerodynamic disadvantages of wider tires might be greater. Does that mean that 31 mm tires are a fine choice for riding at moderate speeds, but that you would be better off on 25 mm tires when you go faster?

We tested both 25 and 31 mm-wide tires in the wind tunnel. The result: The raw data showed a 1% increase in wind resistance for the wider tires, but the results weren’t statistically significant. Even if we accept them at face value, the added wind resistance is too small to make a noticeable difference. For example, at a very high speed of 40 km/h, decreasing your wind resistance by 1% only adds 0.4% (or 0.14 km/h) to your speed.
What about the heavier weight of wider tires blunting the acceleration of your bike? That doesn’t appear to be a major factor either, since wheel weight is less important than many riders believe. (See this recent post for a discussion of wheel weight on professional racers’ bikes.) If you use smaller 650B wheels, you make up some of the greater weight of a wider tire through a lighter rim.
All this data shows that 31 mm tires roll as fast as 25 mm tires, even on very smooth roads. And when the roads get rougher, the wider tires roll faster.

What about even wider tires? Our on-the-road experience suggests that even 42 mm-wide tires do not roll slower than 25 mm tires (above), but without rigorous testing under controlled conditions, we can not say for sure. We hope to test this soon.
Of course, there are other reasons beyond performance to ride wider tires. You gain comfort. You will incur fewer flats, since you run wider tires at lower pressures, so they roll over obstacles that would get hammered into narrower tires. You’ll be safer, since a wider tire will be less affected by small cracks and railroad tracks.
Most of all, you’ll be enticed to go on small roads that have great scenery and little traffic – roads you might have avoided with narrow tires because the pavement tends to be rough. With more comfortable tires, you can even enjoy roads with no pavement at all!
To answer the question in the headline: Even 42 mm does not yet appear to be “too wide.” Tires wider than that are hard to fit into the rear triangle of a bike without compromising performance (tread/Q factor, chainstay length), so perhaps frame design more than other factors limit the maximum tire width on a performance bike.
Wide tires are one of the few things with a lot of advantages, but very few disadvantages. (There are some downsides to wide tires, which we’ve mentioned here.)
For all our tests, we used tires that had the same casing material, tread pattern, etc., to isolate the effects of tire width. Of course, there are many other factors that influence tire performance, and width is only one important factor. (A wide “touring” tire with a stiff puncture-resistant casing is much slower than a narrow “performance” tire with a supple casing.)
This post is just a summary of the research. The original data and much more detail were published in Bicycle Quarterly. Here are a few resources for further reading:

• A list of blog posts about tires.
• All of Bicycle Quarterly‘s tire tests were summarized in Vol. 11, No. 3.
• Bicycle Quarterly‘s wind tunnel tests were published in Vol. 6, No. 1.
• Index by topic of Bicycle Quarterly technical articles.
• How to determine the widest tire that fits on your bike.
• Compass tires were developed using the results of Bicycle Quarterly‘s tire tests.