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Archive | Tires

FMB Tubulars

Even in these troubled times, most of us continue to ride our bikes, at least here in North America. We’ve been encouraged that even during the ‘shelter-in-place’ in the San Francisco Bay Area, solo bike rides continue to be permitted.

Over the last year, we’ve worked on re-introducing FMB tubulars to the North American market. FMB tubulars perfectly complement to our Rene Herse clinchers. They feature similar no-nonsense tread patterns for road, dirt and mud. FMB’s three casings all offer supple performance, but they vary in their degrees of sidewall protection. Continuer →

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New RH Endurance Tires in 700C and 650B

Many of you asked for more tires with Endurance casings… The 700C x 35 has long been a favorite of gravel racers and all-road riders. Now you can choose between the versatile Standard casing, the superfast Extralight and the tough (but still lightning-fast) Endurance. Continuer →

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Ted King’s Tips for Choosing Gravel Tires

Editor’s Note: ‘Gravel’ means different things in different regions, from the smooth dirt roads of Vermont to the Flint Hills of Kansas. Few riders have as much experience riding and racing all over the world as two-times Dirty Kanza winner Ted King. Here is how the ‘King of Gravel’ chooses his tires.

It’s only in the relatively recent rearview mirror that we see cyclists steering their frankenbikes off the beaten path. “Gravel” as a name wasn’t a genre of riding yet; this was merely riding a bike on pavement and then riding a bike off pavement. Most riders were on two-wheeled amalgamated collections of misfit parts, trying to create what did not yet exist: Riders took the best parts of road and mountain bikes and combined them in a single bike. That was the start of “gravel” as we know it, and it’s quickly becoming something of a rarity in this day and age.

With the burgeoning support of the entire cycling industry behind gravel, and with a hyper-focus on components designed specifically for every style of gravel riding, my inbox is continually filled with questions about my choice for bike parts. Specifically, questions revolving around where the rubber meets the (off) road are the most common. So in an attempt to take a proactive approach, I’m excited to offer Ted’s Tips for Choosing Tires. Continuer →

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Back in Stock: RH Tires with Endurance Casings

As it can happen with new products, the demand for our Endurance casings has outpaced the supply recently, and some popular models have been out of stock. We’ve stepped up production, and now all tire models are back in our warehouse, ready to ship. That includes the 700C x 38 mm Barlow Pass, a favorite of gravel racers… Continuer →

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Enve and Zipp hookless rims and Rene Herse tires

Rene Herse tires are safe to use on hookless rims from Enve and Zipp – even when mounted tubeless. Over the last year, we’ve worked with the engineers from both companies to ensure the full compatibility of our tires with their rims.

Tubeless tires are an emerging technology. They’ve been around for decades on cars and motorcycles, and they’ve taken over mountain biking in a storm, too. These are all relatively stiff tires that run at relatively low pressures.

Adapting the technology to road, all-road and gravel bikes has posed special challenges. The supple high-performance tires we love have less casing stiffness, and they run at somewhat higher pressures. (Few cars, motorcycles and mountain bikes exceed 2.5 bar/35 psi.) Both factors combine to create much greater forces at the tire/rim interface than on other vehicles. Continuer →

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Myth 19: 700C Wheels Are Faster

When we started this series to celebrate Bicycle Quarterly’s 15th anniversary, we thought we’d eventually run out of myths. But it seems that new ones are created as fast as we can debunk old ones. The latest is “700C wheels roll faster than 650B.”

This is stated with the same certitude as the old “narrow tires are faster” – and it’s just as wrong. Simply put, there is no evidence that 700C wheels roll faster than 650B (or 26″), and much data to show that they all roll at essentially the same speed. Continuer →

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Are gravel bikes slower than road bikes?

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.” Continuer →

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How Fast are Rene Herse Tires?

How fast are our tires? We know that the casing, and not the width, determines a tire’s speed. When I rode Paris-Brest-Paris on 42 mm-wide tires (above), I knew that I wasn’t giving up any speed over narrower rubber. But in absolute terms, how fast are our Rene Herse tires?

Manufacturers’ claims always are taken with a grain of salt… So let’s look at two independent tests of our tires. They still list the old ‘Compass’ name, but the tires tested were the same as the current Rene Herse models.

The respected German magazine TOUR found our Bon Jon Pass as one of the five fastest tires they’ve ever tested. TOUR tested the Standard model. The much more supple and speedy Extralight would have fared even better.

TOUR’s test rig is a pendulum that rolls the tires back and forth. The longer the pendulum swings, the lower the rolling resistance.

Like all tests that don’t include a rider, this test measures only losses due to deformation of the tire (hysteretic losses). In the real world, there are also suspension losses as vibrations are absorbed by the bike and the rider. Wide tires vibrate less than narrow ones, so they tend to roll even faster than these tests suggest.

In any case, the result is clear: In TOUR’s test, the Bon Jon Pass is one of the fastest tires in the world, closely matching the best racing tires. Being 9-12 mm wider than the racing tires doesn’t make the Bon Jon Pass any slower.

What’s the best gravel tire? – 10 models in comparison

How about comparing our tires to other wide tires? Gran Fondo magazine recently tested ten popular gravel tires. Rolling resistance (and puncture resistance) were tested by Schwalbe’s engineers in the company’s test lab.

Our Barlow Pass Extralight had the lowest rolling resistance (red bar) of all tires in the test. (100% is the best in the test.)

The engineers at TOUR and Schwalbe are among the most respected in the cycling world. Their tests show that our casings are among the most supple, and roll as fast or faster than the best tires in the world.

On real roads, the advantage of supple tires is even greater: Not only do they absorb less energy as they flex, they also vibrate less. And that reduces the suspension losses. Both effects work in tandem: Supple tires have less tire deformation and less vibration. As a result, the greater speed of supple, wide tires becomes very noticeable when you ride on real roads. When you try different tires back-to-back, you realize that tires are the biggest performance upgrade you can make to your bike.

A little more about the Gran Fondo test: The testers were impressed by the “superb levels of comfort” of the Barlow Pass and called it “almost as nice as flying.” They also were surprised how much grip the supple tires offered on gravel and dry dirt roads. Of course, reading that makes us happy, even if it just confirms what we’ve found in our own testing.

Further reading:

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The long road to dual-purpose knobbies


When Ted King recently won the Epic 150 gravel race in Missouri on our Rene Herse Steilacoom tires, many were surprised that he ran knobbies on a fast course. But there were a few muddy corners where the knobs would provide valuable grip, and Ted knew that on the smooth portions of the course, he wouldn’t give up performance, thanks to our innovative tread pattern.

When we developed our ‘dual-purpose’ knobbies, I wanted tires that roll and corner as well on pavement as they grip in mud. I can see you shaking your head: “Impossible!” For grip in mud, you need knobs. On pavement, knobs flex as the tire rolls, consuming energy and slowing the bike. And when leaning the bike into a paved turn, knobs squirm, which reduces grip and makes cornering unpredictable.


That is why for most of the history of cycling, there were knobby tires for cyclocross, and smooth tires for the road. Nobody thought of riding knobbies on the road…


When mountain bikes became popular in the 1980s, knobby tires were part of their rugged appeal, but most entry-level mtbs were ridden around town. Tire makers started to think about making knobbies that perform better on pavement. The solution was obvious: Make them less ‘knobby’ by spacing the knobs more closely. In the center of the tire, the knobs often were linked to form a continuous ‘center ridge.’ This distributed the rider’s weight over more knobs and reduced the squirm. On pavement, this worked to a degree – these tires squirmed less, but they were still no high-performance tires.

There was a drawback: When you really need knobs to dig into soft soil, mud or snow, the closely spaced knobs clog up. You spin as you would on a slick tire. These days, you don’t find many tires with center ridges and densely spaced knobs any longer, because they are worse than road tires on pavement, and just as bad in mud.


The next idea was to remove the knobs in the center of the tread. That way, you roll mostly on smooth rubber when going straight, which reduces the tire’s resistance. As long as you go straight, this works OK. When you corner on pavement, the tire grips fine at first. Then you climb onto the knobs and suddenly lose traction. It’s not exactly what you want from a high-performance tire…

If these tires had excellent performance in mud, it might be worth the trade-off. But when grip is reduced,  you can’t lean the bike far enough to use the corner knobs. Even if the tire sinks deep into the mud, there are too few knobs to really make a difference – you don’t get much extra traction. Once more, you end up with a tire that corners like a knobby on pavement, but slides like a slick tire in mud.


How can you get around this problem? On the face of it, the answer is simple: Make the knobs large enough that they don’t squirm, yet space them far enough that the mud clears from in between. The knob shape itself doesn’t make much of a difference – the engineers of several tire makers have acknowledged privately that the different knob shapes are “mostly for style.”

Coming up with the idea was easy, but the devil is always in the details. Can a knob be large enough not to squirm, yet small enough to dig into the mud? Our testing indicated that this was possible. How much open space do you need to clear mud? Fortunately, decades of racing cyclocross on various tires had given us a good idea of where to start with our testing.

How to make a knobby tire that corners predictably? You arrange the knobs so that there always is the same amount of rubber on the road, no matter how hard you lean the bike. That way, the traction is always the same, rather than suddenly breaking away as you lean and get on the edge of a line of knobs. It’s logical, and yet I haven’t seen any other knobby tire that follows that principle.


The hardest part was combining all these parameters into a single tread pattern. It took a lot of experimentation, but the result has surprised everybody. On a fast paved group ride, these tires perform as well as many racing tires. I know this sounds like hyperbole, but riders who’ve tried these tires agree. Gravel racer Ted King wrote to us: “On pavement, they’re incredibly smooth. The tread pattern is awesome  it’s really cool how deceptively simple the Steilacoom tread is, yet how well the tires work.” One independent reviewer even set Strava KOMs on his Steilacooms.


The cornering is easier to show. I can’t think of any other knobby tire that I’d dare to lean over that far on pavement. And I wasn’t even pushing the limits…


How about the performance in mud? After three seasons of cyclocross on Steilacooms, everybody agrees: They grip as well as the best cyclocross tires developed specifically for muddy courses.

Surely, there must be some drawbacks – otherwise, we should all be riding these knobbies all the time!

On the straights, the knobs have less ‘pneumatic trail,’ because there isn’t a continuous surface of rubber on the road. That means they don’t have quite the same straight-line stability as smooth-treaded tires in the same width. You may not even notice this, because the effect is small.

The knobs add a little weight, too, but once again, the effect is small, because the tread between the knobs is thinner – that part of the tire doesn’t wear, so we don’t need extra rubber there. Our knobbies weigh between 45 and 60 g more than their smooth-treaded cousins in the Rene Herse tire program. Thanks to our lightweight casings, they’re still lighter than almost any other tire with the same width.

As to the rolling resistance, the difference is so small that you won’t notice on the road even on a spirited ride with a group of well-matched friends. The biggest disadvantage may be that, like Ted King at the Epic 150, you’ll have people wonder why you ride “so much tire” on rides that include significant pavement…


I’m excited about the Rene Herse dual-purpose knobbies, because they make rides possible that were difficult to imagine before: rides that combine paved roads with muddy trails and even snow. We no longer have to choose between on-road performance and off-pavement grip. Once again, we’re pushing the limits of what our all-road bikes can do.
Our dual-purpose knobbies are available in three models:

  • 700C x 38 mm Steilacoom
  • 700C x 42 mm Hurricane Ridge
  • 650B x 42 mm Pumpkin Ridge
  • 650B x 48 mm Juniper Ridge

Photo credit: Dustin Michelson (Photo 1).

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Safety Advice: Non-Standard Rims and Rene Herse Tires


Safety advice: Rene Herse tires are designed for rims that meet the ETRTO standard, specifically:

  • G height: 5.2 – 6.5 mm
  • Sidewalls with hooks.

Rims that do not meet the current standards – especially hookless rims and rims with sidewalls that have G heights of less than 5.0 mm – are not recommended for use with Rene Herse tires. This is especially important when installing your tires tubeless. Our testing has found that tires mounted tubeless on hookless rims or on rims with lower-than-standard G heights have a less-than-adequate margin of safety against blow-offs. All warranties are void when Rene Herse tires are installed on rims that do not meet the current ETRTO standards.

The ETRTO (European Tire and Rim Technical Organization) sets most standards for car and bicycle tires and wheels, not just for Europe, but for the entire world. Currently, the ETRTO standards are the only standards that exist for tubeless bicycle wheels. They specify the G height of the sidewall at 5.2 mm (for tubeless) and 5.5 – 6.5 mm (for tubes, depending on the rim width). The sidewall must have a hook.

Like most tire makers, we design our tires to meet the ETRTO standards. Why don’t all rim makers follow these standards, too?

In the past, there were some poorly designed rims with overly deep wells and G heights larger than 6.5 mm. Fortunately, these rims have long been discontinued, and cyclists who still have them usually know how to deal with the problems that occur when trying to mount tires on them (as much as this is possible).

These days, we see some rims with G heights that are smaller than the ETRTO standard and no hooks. Even though these rims do not meet the current standards, this makes sense for mountain bikes with carbon rims: A tall sidewall makes the rim vulnerable if the tire bottoms out while the bike is leaning over. The tall G height provides a long lever that can crack the rim. Why hookless? Mostly because the hook is difficult to make with carbon fiber: It requires a complex 3-piece mold for the rim bed.

A ‘hookless’ rim (above) with a shorter G height is stronger and less expensive to make. Stiff mountain bike tires are inflated to ultra-low pressures. They won’t blow off their rims even if there isn’t much sidewall to hold them on. So the non-standard rims have worked fine for mountain bikes. These mountain bike rims usually come with low maximum pressure ratings.

Recently, some rim makers have introduced ‘gravel’ or ‘all-road’ rims that are made to mountain bike standards: without hooks and with low G heights. Unfortunately, these rims don’t work well for high-performance all-road tires.


We can’t say it often enough: The bikes we ride aren’t mountain bikes. They are road bikes with really wide tires. Perhaps it’s not surprising that the industry still misunderstands what gravel and all-road riding is all about: The sport has grown from the bottom up, when riders like us headed into the mountains, found new roads and designed new equipment to ride on them. Some of the established manufacturers are getting it, but many still think inside their traditional boxes of ‘Road’ and ‘Mountain’ bikes. More often than not, they’ve put our bikes into the ‘Mountain’ category.

Here at Rene Herse Cycles, we’ve always thought of them as ‘road’ bikes – that is why we coined the term ‘all-road bike’ for them. Even though my Firefly (above) has 26″ wheels, it’s not a drop-bar mountain bike. It’s a road bike with wide tires. We ride on road tires, and we need road rims for them.

That is why hookless mountain bike rims don’t work well for all-road wheels. All-road tires are supple, and they run at higher pressures than mountain bike tires. This requires an additional margin of safety.

We tested a 650B x 48 mm Switchback Hill tire on a carbon mountain bike wheel with a hookless rim and a G height 0f 5.0 mm. We mounted the tire tubeless, but without sealant (for obvious reasons). The rim is rated to 40 psi, and the tire was fine at that pressure. 40 psi isn’t a lot, even for a 48 mm-wide tire. The tire is rated to 55 psi, so we kept inflating to see what would happen. At 58 psi, the tire blew off. We then repeated the experiment with a second tire, and it blew off at 65 psi. This problem is not limited to Rene Herse tires: Other riders have reported similar blow-offs with tires from other makers.

58 psi is a lot of pressure for a 48 mm tire, but when the tolerances stack up in a bad way (slightly oversize tire and slightly undersize rim) or when the tire isn’t installed perfectly, the blow-off pressure will be lower. Then the margin of safety won’t be adequate. This is neither the tire nor the rim’s fault. It’s simply using the wrong rim for a supple all-road tire.


How much of a difference does the hook make? We put one of the tires on a HED Belgium Plus rim. The G height is the same as on the carbon rim we tested (5.0 mm), but the HED rim has a hook. Even though this is the same tire that already had blown off the rim once, it stayed on at 75 psi. The is no doubt: The hook has a crucial function in keeping the tire on the rim. Other rim and tire makers have tested and found the same: The hook significantly increases the pressure at which the tire safely stays on the rim.

Fortunately, there is another way to increase the margin of safety: Use inner tubes. We put the tire back on the hookless mountain bike wheel, this time with a tube. We inflated it to 75 psi and left it overnight. Nothing happened. We were surprised that even the violent explosion had not stretched the tire, but these beads are strong. (However, we don’t recommend re-using a tire that has blown off the rim.) That is good news: Hookless rims tend to work better when used with tubes – even though we cannot officially recommend them, since they don’t meet the ETRTO standards to which our tires are designed

Conclusion: All-road bikes are road bikes, and all-road tires are road tires: They should be mounted on road wheels. When you buy new wheels, make sure the rims are designed to the ETRTO standards, and not to mountain bike standards: You want a hook and a G height of 5.2 – 6.5 mm. If your wheels already are equipped with hookless rims, using tubes can increase your margin of safety. And check the maximum pressure ratings, not just of the tire, but also the rim: Don’t exceed them!


Tubeless is great technology – had I used inner tubes on the ride across Odarumi Pass in Japan (above), I probably would have pinch-flatted several times. But tubeless is also an emerging technology. We’ve had to learn how to mount tires (huge blasts with compressors are a sign that the rim is undersize) and how much sealant we need (more than we usually think). Now we are discovering that hookless mtb-style rims don’t work well with all-road tires.

Why do tubeless tires blow off so much more easily? Without a tube reinforcing the joint between rim and tire, it’s much easier for air pressure to force its way out. It’s still extremely rare for tires to blow off, but, with tubeless tires becoming more popular, there have been more incidents than before. They affect all brands of tires – a little while ago, a wheel maker told me of two different tires from a big German tire maker that had blown off his hookless rims that day.

Also remember that tubeless-compatible tires always need liquid sealant inside. If the sealant dries out completely, the tire can break loose from the rim sidewall and deflate suddenly. This can cause the tire to come off the rim, even if rim and tire are sized correctly.


Safety is our biggest concern, not just for our customers, but also for ourselves, because we ride our bikes hard. We’ll continue to test, and we’ll continue to work with rim makers, to drive tubeless technology forward in a safe and responsible way. The last thing we want to worry about during our adventures is whether our tires will stay on their rims! Fortunately, in almost 100,000 km (60,000 miles) on Rene Herse tires and their predecessors, I’ve not experienced a blowout. We’ll work hard to make it remain that way!

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How to set up tubeless tires


Tubeless tires have eliminated the risk of pinch flats. For riding in really rough terrain, they are a game changer. But like all new technologies, it’s taken some trial-and-error until we figured out how to run bicycle tires tubeless.

Of course, tubeless tires are nothing new. Car tires have been tubeless for decades, but translating that technology to much more flexible and lighter bicycle tires has not been easy. (We don’t want to ride on rubber that’s as stiff and heavy as car tires!) Modern bicycle tires fall into two groups:

  • ‘Tubeless’ tires are covered with a rubber membrane – basically an inner tube is permanently vulcanized into the tire. These tires are airtight. You can just install them, and run them without inner tubes. However, the extra rubber makes them relatively stiff and slow.
  • ‘Tubeless-compatible’ tires are not airtight, and they roll as fast as conventional tires. Their bead has been designed for tubeless installation, so you can run them tubeless – but they require sealant to make the casing air-tight and to seal the tire against the rim. The sealant also will seal small punctures that otherwise would cause a flat. Most Rene Herse tires are ‘tubeless-compatible.’

Key to mounting tubeless tires is the right technique. This is especially important with supple tires. Stiff tires mount easily – just like car tires – because their casing is so stiff that it either touches the rim walls and seals, or it doesn’t.

Supple casings make tires fast and comfortable because they flex easily. This means that they may contact the rim in a few places, and have air gaps in others – making them harder to mount and seal tubeless. They follow the general rule of high-performance components: The tolerances need to be a bit tighter, and working with them requires a little more skill.

It’s not hard to install supple tires tubeless, if you work methodically. Here is how I installed my Rene Herse Extralights tubeless while traveling in Japan, with no access to a workshop and just a few tools.


To mount a tire tubeless, here is what you need: a tubeless valve; a valve core tool; a syringe for injecting the tubeless sealant; sealant; a tire lever; an inner tube; a tubeless-compatible tire. Your rims also must be tubeless-compatible, and covered with tubeless rim tape. It’s good to have extra rim tape on hand.

I only could find Stan’s sealant in Japan. It worked fine, but we recommend Panaracer’s SealSmart because it does a better job sealing the slightly porous sidewalls of supple tires.

You also need a pump to inflate the tire. A floor pump suffices, and in a pinch, you can get away with a frame pump. You do not need an air compressor. In fact, if you use an air compressor to make up for problems in tire/rim fit, your tire may blow off the rim later without warning.

For safe tubeless installation, a good fit between tire and rim is extremely important. Unfortunately, many OEM rims are slightly undersize, because that makes it easier to install tires in the bike assembly plants. (Imagine a rim that is slightly oversize. For a factory that needs to mount 10,000 tires a month, spending five extra minutes per tire would be a total disaster. That is why OEM rims tend to run small, and never should be larger than spec. OEM tires are installed with tubes, where a slightly undersize rim doesn’t pose a problem.)


If your tire goes on easily, the rim is undersized. Don’t try to install the tire. It may work fine at first, but it can blow off the rim without warning. If this happens in your workshop, it’s just a nuisance (and a big mess). If it happens on the road, the consequences can be far worse.

If your rim is undersize, it’s not the end of the world – there is a solution. Build up the rim bed with additional layers of rim tape. Some mechanics use Gorilla Tape for the extra layers – it’s a little thicker than standard tubeless tape. (Always use tubeless tape as the first layer on the rim to seal the spoke holes.) The tire should be a slightly tight fit. This makes sure that it seats correctly and doesn’t blow off the rim later.

When installing tires, make sure that the bead is in the rim well (above) all around before you lift the last part of the bead over the rim edge. The well is there to provide slack for the bead – the rim’s diameter is smaller in the center than toward the rim walls. With supple tires and tubeless rims, parts of the bead can end up on the shelf when you mount the tire. Push the bead into the rim well all around the tire – then the last bit of the bead will slip easily over the sidewall.

If you use a floor pump to seat the tire, install a tube first. This seats the beads and gives the tire its shape. Make sure both beads pop into place. Then unseat one bead (the one that popped into place first) by pushing it into the rim well, and remove the tube.


Install the tubeless valve. Don’t forget the valve nut that holds the valve in place. It pulls the valve’s rubber cone into the rim’s hole to create a tight seal. Don’t overtighten the nut: If the valve gets clogged with sealant or the tubeless setup fails, you’ll need to be able to remove the valve on the road to install a tube.


Before you inflate the tire, seat the bead as far around the rim as possible, starting at the valve.


Pull the tire upward and move the bead outward, until it sits on the shelf next to the rim wall.


Continue until the tire is too tight to pull upward. The remaining air gap is small and furthest from the valve. It will seal as the pressure pushes the tire outward.


Inflate the tire ‘dry’ without sealant at first. That way, if you need to remove the tire to add more rim tape, there won’t be messy sealant inside. Pump quickly to build up pressure faster than the air escapes.


Watch the tire as it seats. On the left, the line molded into the tire sidewall is still hidden by the rim wall. The bead hasn’t emerged from the rim’s well yet. Keep pumping until you hear a loud ‘pop’ as the tire seats.

On the right, you can see all of the line that is molded into the sidewall. Make sure it’s parallel to the rim edge all around the tire. Check this on both sides. If it’s OK, then the tire is seated on the rim.

If the tire doesn’t seat, take it off, and add more rim tape to create a tighter fit and smaller air gaps. If you use an air compressor, the tire should seat easily. If you need huge blasts of air to seat the tire, then the rim is too small. Build up the rim with extra tape, rather than risk a blow-out in the future.


Now the tire is inflated and looks great, but air will escape through small cracks and microscopic holes. To seal the tire, add sealant. Let out the air and unscrew the valve core. The beads will remain seated. (If a bead comes unseated now, it wasn’t properly seated in the first place.)


Turn the wheel so the valve is neither at the top nor at the bottom of the tire, where sealant would spray back out of the valve. Shake the sealant vigorously for a minute, so the solids are in suspension. Don’t skimp on this step! Otherwise, you’ll just inject colored water into the tire, and it won’t seal.

For our Rene Herse tires, we recommend Panaracer’s Seal Smart. It seems to seal the supple sidewalls better than other brands. When mounting the tires in the photos, I was in Japan, and Panaracer’s sealant had not yet been released. I couldn’t find our second choice, Orange Seal. So I used Stan’s. It worked fine.

Make sure to use enough sealant. Wide tires have a lot of surface area. To seal properly, you need about 90 ml (3 oz) – one to one-and-a-half of the bottles shown in the photo.


Replace the valve core. When I installed the tires tubeless in Tokyo, I didn’t have a valve core tool. A small adjustable wrench will do the job in a pinch.


Inflate the tire again. Since it’s already seated, this will be easy.


Close the valve. Now the tire looks ready to roll, but the sealant must still be distributed to seal all the microscopic gaps. Just riding the tire isn’t enough to stop all the tiny leaks.


There are different techniques for distributing the sealant. I’ve found this one to work best, because it methodically works the sealant into every part of the tire and rim interface. Make sure you have enough room. Don’t hit the ceiling, furniture, or your head. (Don’t ask how I know!)

Hold the wheel steady (left), so the sealant collects at the bottom. Quickly move the wheel upward (center). Centrifugal force will keep the sealant right under the tire tread. Hold the wheel over your head (right), still slightly tilted away from you. Now the sealant runs downward, covers the sidewall, and seeps into the gap between tire and rim.

Rotate the wheel a few degrees and repeat. (Start with the valve at the bottom, so you have a reference point.) Once you’ve worked all the way around the tire, turn the wheel around, and repeat on the other side. Now your tire is ready to ride. Riding it immediately will help distribute the sealant further.

If your tire loses air overnight, check it like a leaky inner tube. Often, you can hear and feel the air escape. Hold the tire so that gravity pulls the sealant into the leak. If it doesn’t seal, there may not be enough sealant in the tire.


Now your tubeless tire is ready to roll. Enjoy the ride!

Tubeless tips:

  • Panaracer Smart Seal works best to seal the supple casings of our Rene Herse tires.
  • Use enough sealant. When the mechanics at Paul Camp prepped bikes for their press fleet, they put 3 oz. (90 ml) in each tire, because they didn’t want trouble. More sealant makes your tires slower, but if your tire runs out of sealant, it’ll start losing air. If you want to go fast and don’t need to worry about pinch flats, use inner tubes. (Click here to read more about why tubeless tires are slower.)
  • Sealant needs to be topped up at least once a month. Supple tires push and pull slightly against the rim sidewall as the wheel rotates. If the sealant dries out, air will start leaking. Then the tire can suddenly break loose from the rim wall and lose all its air. Don’t ride your tires when there is no liquid sealant left inside – the sealant not only acts as flat protection, but it constantly seals the tire against the rim.
  • Use only new tires for tubeless installation. As a tire is ridden, the sidewalls flex and become more porous, making them harder to seal.
  • If you want the flat protection offered by the sealant without the hassle of tubeless installation, you can put sealant in your inner tubes. This also works best with new tires, and you obviously need tubes with removable valve cores. (The tubes we sell have removable cores.) Simply put some sealant inside the tube, and it’ll seal many punctures.
  • Most Rene Herse tires are tubeless-compatible. They are marked ‘TC’ on the tire label. The label on the package also says ‘Tubeless-Compatible.’

Click here for more information about Rene Herse tires.

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Myth 16: Higher Tire Pressure is Faster


This used to be one of the first things you learned as a cyclist: If you want to go fast, make sure your tires are pumped up to the maximum pressure. The harder your tires are inflated, the faster they roll.

We now know that this isn’t true. The realization that tire pressure does not affect performance is the key to the revolution that has swept through the cycling world in recent years. Without this new-found knowledge, all-road bikes and their supple, wide tires would make no sense at all. Here is how it works.

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A knobby faster than most road 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.

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Myth 7: Tubeless Tires Roll Faster


When tubeless tires first became available, they were designed for mountain bikes and it was their resistance to pinch flats (above) that made them popular. Off-road, there are few nails or broken bottles that can cause punctures (and even those usually will be pushed into the soft ground rather than puncture the tire), but rims can bottom out on sharp rocks and other obstacles. So much so, in fact, that top mountain bike racers used to race on tubular tires – because tubular rims make pinch flats less likely. Eliminating tubes did the same, and while you still could ‘burp’ the tire, in general, tubeless allowed running lower pressures with fewer problems. Continuer →

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One of the 5 Fastest Tires in the World


Recently, the German magazine TOUR published a table showing the ‘five fastest tires in the world.’ We are excited to see our Rene Herse Bon Jon Pass 700C x 35 mm tires (back then still under the Compass label) on this list, in the company of the fastest racing tires. A 35 mm-wide tire on a list that otherwise includes only tires between 23 and 26 mm wide! That by itself is already cause for celebration. It means that our casings really are among the very fastest in the world.
And since all our tires use the same casings and construction, TOUR’s results apply not just to the Bon Jon Pass, but to all Rene Herse tires. I was surprised that they tested the Standard casing. I would love for them to test the Extralight, which we know from our own experience to be even faster.

What is interesting is that the Rene Herse tire scored superbly on smooth asphalt (light gray bars), but a little less well on rough asphalt (dark bars). This doesn’t match our experience, where wider tires provide advantages especially on rough roads. The reason is simple: TOUR tested without a rider on the bike. This measures the hysteretic losses in the tire, but it neglects the (much more important) suspension losses that occur as the rider’s body and bike vibrate. (Click here to learn more about suspension losses.)
This means that TOUR’s testing overlooks one of the main advantages of wide tires: their superior comfort, which also makes them faster. In other words, with a rider on the bike, especially on rough asphalt, the Rene Herse tire probably is even faster than it appears in TOUR’s testing.
We are proud that the Rene Herse Bon Jon Pass scored so well, especially since it is intended as an all-round tire, not an all-out racing tire. The Bon Jon Pass is suitable for gravel racing and has 3 mm-thick tread for many miles on the road. Compare that to the Vittoria with its 0.8 mm-thick tread, which is intended only for time trials, and even then, it’ll wear out quickly.

The excellent performance of the Rene Herse tire shows once again why wide tires have revolutionized cycling: You wouldn’t want to ride the other tires on TOUR’s list on anything but the smoothest, cleanest roads for fear of flats and premature wear. And yet with wider tires, we can ride some of the world’s fastest tires on the backroads where cycling is at its most beautiful.
Further reading:

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Myths in Cycling (1): Wider Tires Are Slower


When we started to publish Bicycle Quarterly 15 years ago, it seemed that most of the technical aspects of bicycles were well-established. And yet, as we tested many different bikes, we started to question many of the things we had accepted as ‘facts.’ To celebrate our 15th anniversary, we’ll look at some of these myths. We’ll explain why we (and everybody else) used to believe them, and how things really work. Let’s start this series with the biggest one:

Myth 1: Wider Tires Are Slower Continuer →

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Minimum Tire Pressure

Hahn_Paso

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?

contact_patch

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.

paso_cortes_descent

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.

BJPASS_result-750x481

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.
tire_pressure_chart_psi

Or if you prefer metric values:

tire_pressure_chart_bar
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:

Photo credit: Cyclocross magazine (damaged casing)

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The Missing Piece: Suspension Losses

old_road_to_mexico

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.

RumbleStrip

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?

basketball

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.

tire_push_off_2

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?

rough_road

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.

rumble_smooth

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.

diverge_skagit

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.

tekne_gravel

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:

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

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Tire Pressure Take-Home

un-meeting_uphill

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?
tire_drop
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.

golden_gardens

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.

track_tire_test

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.

hahn_un-meeting

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:

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How Wide a Tire Can I Run?

Fork_clearance

Many cyclists want to ride on wider tires, but are limited by the clearances of their bikes. So they want to use the widest tires their bike can fit. How do you determine your bike’s maximum tire width?

You need a set of calipers (below). If you don’t have any, bike shops have them. Please leave a generous tip if you ask a shop mechanic to help you with this!

calipers

1. Measure your current tires

Measure the width of your current tires. Be careful not to pinch the tire. Instead, increase the opening of the calipers by 0.5 mm increments, and check whether the opening has play when it is slipped over the tire. (The calipers “rattle” when you move them.) When this happens, the calipers are set just a tad larger than the actual width of your tires. Use this measurement as your current tire width.

If you pinch the tire with the calipers, you may get a measurement that is up to 2 mm narrower. Also don’t use the width that is printed on the side of your current tires. It’s often not accurate enough for this purpose.

chainstay_clearance

2. Check your clearances

Check all around your wheels how much clearance you have between tire and frame/fork/brakes. Most important are:

  • fork crown
  • brake calipers (front and rear): squeeze your brakes to get the clearance when braking
  • chainstays
  • seatstays can limit the clearances on some bikes.
  • fenders: often, you can adjust the fenders to eliminate a tight spot.

I recommend a minimum of 3 mm clearance between your tires and the closest part of your bike. Any less, and you risk having your tire rub under hard acceleration or if the wheel develops a slight wobble.

3. Calculate your maximum tire width

Start with the smallest clearance between your existing tire and bike. Then deduct the tightest clearance, 3 mm, to get the existing available clearance for your wider tire. Multiply this by 2 (you have that much room on both sides of the tire), add the current tire width, and you get the maximum tire width:

max. tire width = 2 x (tightest clearance – 3 mm) + current tire width

Example: Your current tires are 29 mm wide. You have 5 mm clearance at the tightest spot. That leaves 2 mm available clearance. You can run 4 mm wider tires than your current ones. Your maximum tire width is 33 mm:

max. tire width (example) = 2 x (5 mm – 3 mm) + 29 mm = 33 mm

This assumes that your new tires have a similar height-to-width ratio as your existing ones. Some inexpensive tires can be much taller than they are wide, but high-end tires usually are relatively round, and this formula works well.

If you find yourself between two available tire sizes, I suggest using the narrower tire. High-end tires tend to expand over time as the casing “relaxes,” and you don’t want your tire to rub every time you rise out of the saddle and flex your wheel. If you find that you still have extra clearance, you can go up one more size when your new tires wear out.

By the way, the bike in the photos does not appear to have extra clearance, so if your bike looks like that, you probably should stick with the tire width you have. You still can improve the ride and performance of your bike by using more supple tires with higher-quality casings.

Photo credits: Ernie Fong.

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