To celebrate 15 years of Bicycle Quarterly, we are examining myths in cycling – things that we (and most others) used to believe, but which we have found to be not true. Today, let’s look at tire tread: Tread patterns matter – they can make a difference – even on the road.

“Bicycles don’t hydroplane,” declared some experts many years ago. “Hence, tire tread patterns don’t matter on the road.” The first part is true – even wide bicycle tires are too narrow to lose traction due to hydroplaning – but tire tread doesn’t only serve to evacuate water from the tire/road interface.

In fact, the tread of bicycle tires has other purposes. I once cycled on the polished stone that surrounded a college library, and I was surprised by the lack of grip: I crashed. Even though I was unhurt, I learned the hard way that the coefficient of friction between our tires and the rocks that make up the road surface isn’t very high. Yet we don’t crash on roads made from the same rocks, but in the form of rougher aggregate in pavement. What happens is that tire and road interlock to create grip.

If our grip came only from pure friction, the size of the contact patch wouldn’t matter. Physics tells us that if you double a tire’s width, it will be pushed into the road surface with half as much force – the two cancel each other. Yet race cars run ultra-wide tires because they provide more grip. What is going on?

Tires interlock with the road surface. Imagine each little surface irregularity like a spike that pushes into the tire. The wider the tire, the more surface irregularities it touches; hence it has more grip. A softer tire also has more grip because the road surfaces pushes deeper into the tire. That is why the tires of race cars use very soft rubber, and why wider bicycle tires at lower pressures offer more grip than narrow ‘racing’ rubber at higher pressures.

There is another way to increase the interlocking between tire and road: provide edges on the tire that ‘hook up’ with the road surface irregularities. Each edge provides a point where a road irregularity can hook up. The more edges you have, the better the tire hooks up.

This isn’t a new idea – back in the days when rubber compounds were less grippy, all racing tires used treads that were similar to the Rene Herse tire above. I often wondered about these ubiquitous tread patterns, until I found the answer in Bike Tech, a long-defunct newsletter about bicycle technology. Under the headline “The Importance of Real-World Results,” a Michelin engineer described the interlocking mechanism, and explained that, especially in the wet, interlocking is what gives a tire much of its grip.(1) If the surface is ‘greasy’ when it first rains after a long period of dry weather, friction is even less, and the interlocking is even more important.

That matches my experience. In theory, the friction between road and tire should be less than half when it’s lubricated with water, and yet we can corner at about 2/3 of the ‘dry’ speed in the wet – at least on good tires (and when the road is just wet, rather than greasy).

This doesn’t mean that the rubber compound of the tire tread doesn’t matter – it’s a crucial element in making the tire grip on dry and wet roads. At Rene Herse, we are excited to use some of the grippiest, yet long-wearing, rubber in the tire business. That way, we can optimize the grip of our tires in every way.

The result speaks for itself: The photo shows me cornering hard on a streaming wet road, yet I wasn’t taking any risks during that descent. There aren’t many tires I’d lean over that far in those conditions!

Why don’t cars or motorcycles use ribs to interlock with the road? They have too much power. A drifting Moto GP rider (above) would just shred those ribs. Motorbikes and cars also are heavy enough to push their tires into the road surface, where bicycles tend to skitter across the surface.

On a bicycle tire, distinct parts of the tread serve different purposes.

The center tread doesn’t matter much – you are going straight when it touches the road. This is also the only part that wears significantly, so we put some fine ribs on our Rene Herse tires that act as wear indicators: When they become completely smooth, then your tire is at about half of its life expectancy.

Furthermore, some tests have found evidence that a very fine tread pattern can make the tire faster, because it conforms more easily to micro-irregularities of the road surface and reduces the vibrations of the bike. So it makes sense to have a fine tread in the center.

The shoulders of the tires are important for cornering traction. This is where we put our ‘file’ or ‘chevron’ tread pattern for optimum grip. There is no magic to this, and these ribs aren’t directional – the point is just to have as many as possible to hook up with the road surface, but keep them large enough that they don’t just squirm out of the way.

Finally, you have the edges of the tire, which usually don’t touch the road – bicycles simply can’t lean over as far as a Moto GP racer. Here, the tread only serves to protect the tire’s casing from rocks and other obstacles. This tread can be smooth.

It’s all quite logical, and easy to experience on the road. Then why don’t all tires have a tread pattern that is optimized for grip? I suspect it’s hard to replicate the interlocking effect in the lab. But when you ride on real roads, you’ll notice the difference!

Update 11/17/2020: We’ve just published our new book ‘The All-Road Bike Revolution’ with all the research that has changed cycling in recent years. Find out why wide tires can be fast, how to find a frame that optimizes your power output, and how to get a bike that handles like an extension of your body. More information is here.

Notes: (1) Aaron, M., 1988: Importance of Real-World Results. Bike Tech, October 1988, p. 5.

• This argument makes intuitive sense, but is there any way to test it empirically in the same way you tested rolling resistance versus tire width? When I read “better grip in corners” this implies that an inferior tread pattern or rubber compound would cause you to slip or crash – and thus to verify this it is necessary to push the tire to the point where it starts to slip, under controlled conditions of temperature, road surface, rider weight and cornering technique, etc.

February 22, 2018 at 5:48 am
• Testing grip is difficult, because a rider’s inputs and also the micro-conditions of the road surface are so variable. TOUR magazine in Germany tried different ways to test this, first by pulling a wheel in a fork behind a car and turning it sideways until it lost grip. This didn’t produce reproducible results, so they then built an adult scooter and had a stuntman roll down a hill with a corner. With each run, the rider tightened the radius until the tires lost grip, and he crashed. That didn’t produce good results, either, and they basically gave up.
More anecdotally, we used to ride ‘shaved’ tires with the tread removed for better performance in the days when 650B tires had thick tread. I crashed twice on the shaved tires, but never on the ‘standard’ ones, even thought I rode many more miles on the ‘standard’ tires. Also, when I first tested our Compass tires with the optimized tread pattern, I almost ran into the inside curb on a corner I take every morning, because the tire cornered on a tighter radius than I was prepared for. All this isn’t statistically significant, but it seems to confirm the hypothesis nonetheless.

February 22, 2018 at 7:30 am
• Testing tire grip is not difficult:
Take a bike, attach a sidewheel and a small electric motor.
Rent a skid pad and go defined circles. Measure max speed before sliding.

February 22, 2018 at 8:59 am
• That is what TOUR essentially tried to do, and they weren’t successful in getting reproducible results. The rider inputs may be too variable…

February 22, 2018 at 9:08 am
• JWilli

Interesting article! Timely because I was going to ask you what the differences are in the Compass tire (Bon Jon/Babyshoe) and the Gravel King (not the SK)?
Thanks!

February 22, 2018 at 6:28 am
• I put that question to Jeff Zell of Panaracer USA. His reply: “The Gravel Kings and the Compass tires are two different types of tires. The reason that Compass tires are so successful is that Jan and Compass had a clear vision for what they wanted 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 are looking for the ultimate performance, you’ll choose Compass, while Panaracer’s tires are intended for a wider audience that needs more puncture and sidewall protection.”
As the name implies, the Gravel King is designed for riding on rough gravel, and thus a bit overbuilt for riding on the road. The Compass tires are designed for riding on the road, but they are fine (and offer superior performance) on gravel, provided the rider lets the bike move around and doesn’t force it into the rocks that could cut the sidewalls.

February 22, 2018 at 6:54 pm

The listed weight of the 650×1.75 (so similar to babyshoe pass) is actually lighter than the compass ultralight equivalent (350 vs 373 g) . I wonder if the tread is thinner or if the weight claim is just a bit outlandish?

February 25, 2018 at 8:08 am
• I talked to Panaracer about this, and the answer is both: The tread is thinner – which means that the Gravel King won’t last as long as a Compass tire – and the weights are based on the engineers’ calculations, rather than the actual weights, which are about 10% heavier.

February 25, 2018 at 8:54 am
• Tom G

Regarding wear indicators: one of the major tire brands, can’t remember which, has a different color rubber underneath the main layer. When the tire is wearing thin, the second (brighter) color shows through. Seems like such a simple idea but perhaps it’s harder to get color into rubber than I think?

February 22, 2018 at 7:03 am
• We talked about that to Panaracer. It’s possible, but it would require a thicker tread, which would reduce the tires’ performance.

February 22, 2018 at 9:12 am
• Bill Schairer

Years ago while descending from a Canadian Rockies pass on our fully loaded tandem in the rain the bike was moving all over the place. I was quite un-nerved and strongly requested that the stoker sit still. She insisted she was. I do not recall any unusual wind. I assumed then and now that we were hydroplaning despite having read since that that is impossible. One such claim included a reference to some NASA study so I read that report. My recollection is that the report did NOT rule out partial hydroplaning (and stated as such) and did include all the usual disclaimers that left me with the impression that the report was not nearly as conclusive as it is generally represented as being. My question is, if I was not hydroplaning, at least partially, then what was going on? It is the only time I have ever experienced anything like it on a bicycle and whatever it was, it was very real.

February 22, 2018 at 7:07 am
• If you’ve ever hydroplaned in a car, you will have noticed that it doesn’t move around at all, just continues in the direction you are going – because you have zero grip. It’s like riding on ice.
It’s hard to say what happened in your case, but I suspect you experienced partial loss of grip due to a greasy road. That is what it felt like when we were riding a few weeks ago, and the roads started to freeze just before sunrise. Just a little slip here and there. (We stopped at a café until the sun came up and thawed the road surface.)

February 22, 2018 at 7:34 am
• This tandem behavior could be hydroplaning. Though it is correct that hydroplaning causes cars to go straight, that assumes that all four tires are hydroplaning and equally frictionless. If some of the tires are not hydroplaning, then they can impart forces that cause the car to go in other directions.
In the case of the heavily loaded tandem descending in the rain, if the team is heavily weighted towards the front (heavy captain, light stoker, lightly loaded rear) then the braking forces will unweight the rear wheel. Since hydroplaning is strongly related to the pressure of the contact patch, the unweighting of the rear wheel makes it much more likely to hydroplane than the front. When you add the strong braking forces at the front wheel, an unstable situation similar to a tractor-trailer jackknifing arises.

February 23, 2018 at 8:49 am
• I think if you unweigh the rear of a bike while cornering – much harder to do on a tandem, which tends to slide out with the front wheel under hard braking – you have all kinds of issues, not just hydroplaning. If bicycles really do hydroplane, then we should put car-like tread patterns into their tires. Currently, nobody is doing that, except a few ‘classic’ tire makers that replicate models from an era when there were tires with a zig-zagging tread that was modeled on car tires.

February 23, 2018 at 10:24 am
• Racing cars use wide tyres to dissipate heat… so they can use softer rubber and have it perform at ideal temperatures.

February 22, 2018 at 7:27 am
• How does this change for snow/winter riding where you might encounter ice, slush, and even actual snow on the road? In such conditions, do more “knobby” tires help on the road, or would the small chevrons be just as good? What about on muddy or gravel or mixed terrain?

February 22, 2018 at 7:27 am
• Winter conditions are very variable. On clean, new, grippy snow, the ‘chevron’ tread provides surprising grip, but on wet snow, it’s almost useless. There, you need knobs, and even those can do only so much. On ice, nothing but full studs will give you grip.
For snow and also rides where I may encounter mud, I prefer our ‘dual-purpose’ knobbies, the Steilacoom (700C) and Pumpking Ridge (650B). They roll and corner amazingly well on pavement – I have ridden them in fast-paced all-paved group rides – yet they offer far superior grip on snow and mud.

February 22, 2018 at 7:41 am
• Dr J

I don’t even know why this is considered a “myth” at all. Who would ever claim that tread pattern doesn’t matter on road? There’s a reason we don’t ride on paved roads on tires with chunky “mud” tread. There’s a proper tread for every application. Otherwise all tires would look the same.

February 22, 2018 at 8:03 am
• I read somewhere that the engineers from a big German tire maker said that they only put tread on their tires because consumers preferred treaded tires over slicks. So they just drew up something that looked good, but they acknowledged that their tread didn’t make any difference to the tire’s performance.

February 22, 2018 at 9:06 am
• That does not surprise me. When you look at tire advertising, you see pictures that emphasize and exaggerate the tread pattern along with lots of language containing superlative adjectives. It’s almost just porn. As consumers, we really have no idea which works better. Only real world testing counts. (That’s what’s been impressive with the work that BQ/Compass has been doing.)

February 22, 2018 at 11:55 am
• Jim Jenkins

Continental Gatorskins come to mind…popular, durable, stiff tire, with minimalist tread. I enjoy the Roll-y Pol-y tires from Rivendell, for their checkerboard tread, and, of course Compass for the tread that reminds me of the Seta Campionato del Mondo and Paris Roubaix tires from Clement that we loved so much.

February 22, 2018 at 12:44 pm
• I think it is a very common opinion in the bike industry. Here is a good example.
BTW I find it amazing that this site already has a reference to this blog post.

February 22, 2018 at 4:25 pm
• Maybe not the statement you’re referring to, but in 2015 Continental told Road.cc that “the tread pattern doesn’t make much difference on the road. It has a role in certain circumstances, but it doesn’t do much, unlike off-road when the tread pattern is vital in determining grip on conformable ground”. Source: http://road.cc/content/feature/145111-tech-travel-inside-continental
Schwalbe also seems to conform to the notion, since they produce a number of slicks and semi-slicks like the Kojak.

February 23, 2018 at 2:17 am
• Caleb

One example of a prominent source which claims tread does not matter for on-road use: https://sheldonbrown.com/tires.html.

February 22, 2018 at 9:49 am
• Luis Bernhardt

Years ago, a pretty large and successful bicycle company, Avocet, made slick tires. I think the myth of smooth tread started here, with people like Jobst Brandt extolling their virtues on Sheldon Brown’s site, http://www.sheldonbrown.com/brandt/slicks.html (read the article to understand the thinking at the time). As with most things, the truth is somewhere in between…

February 22, 2018 at 11:03 am
• John C. Wilson

Look at the lean angle Jobst has going in the photo accompanying the article. He’s not racing, he’s a big guy on a big frame, he’s sitting rather high, and still he has lean that does move into moto territory. Look at moto photo in JH article above and regard only wheels, not where the motorcyclist’s body is. Why doesn’t anyone ride this way anymore? I grew up in Criterium Heaven (Upper Midwest in 60s-70s) where we could watch Stetinas and Roger Young and Jeff Bradley and of course Greg give object lessons all summer. They leaned a lot more than the old engineer. Nowadays, quite old myself, if I corner with even a little verve the club is going to tell me to quit showing off, to quit setting a bad example, to dial it back. And I am not good in a corner. Certainly not by 70s standards.
Also the Avocet tires were great. So are the Compass tires.

February 25, 2018 at 11:49 am

• The image of Jobst (above) is really neat, and he must have been a great descender. I think you’ll still see photos of riders cornering like this, when the road is smooth, dry and clean, and temperatures are warm to increase grip. Much of the time these days, we ride on backroads that don’t quite have ideal conditions, so we need to keep a little more in reserve. The photo at the top of this post shows how much more cautious you have to be in the wet, on a cold day, with leaves on the road…

February 26, 2018 at 9:05 am
• Francisco

Jobst Brandt claimed so, for instance.

February 22, 2018 at 11:25 am
• The idea that tread doesn’t matter was the rationale behind Avocet road tires which were completely slick unlike most other tires on the market at the time. It makes a lot more intuitive sense that having tread matters, but the exact pattern of it makes no difference.
Interestingly enough, cross-country ski bases, which face the opposite problem of trying to eliminate grip as much as possible, sometimes have “tread” as well, known as “rilling” or “structure”, for the purpose of breaking the surface tension (what skiers call “suction”) of the liquid water that collects under the weight of the skier at warmer temperatures (above -2C I believe). This has led to an incredible fragmentation of ski types, not only waxable/waxless but now cold/warm as well… and of course a lot of pseudo-scientific claims about the benefits of specific grind patterns!

February 22, 2018 at 12:16 pm
• If motorcycles and cars use soft rubber to make it interlock with the road – wouldn’t bicycle be just waaay to hard if they don’t interlock?
If you reduce contact surface by 50% – don’t you just increase wear by the same 50%? What’s the difference to a softer rubber compound?
Conti does profiles, but absolutely not in the way described by you. Wouldn’t they now how to build tires?
If you compare a profiled tire with the same model shaved – wouldn’t the shaved tire be necessarily be badly designed for having to thread (i.e. compound too hard)?
If your tire need a thread pattern to interlock with the surface – is the rubber compound just tooo hard?

February 22, 2018 at 9:03 am
• Many good questions! Bike tires aren’t too hard to interlock with the road, but the weight of bike and rider is much less than that of a car or even motorcycle.
As to putting faith in the knowledge of big tire companies, these are the guys who told us for decades that narrower tires and higher pressures made you go faster. I’ve often wondered why they went up that blind alley for so long. Why didn’t anybody at Conti, Schwalbe or Michelin just roll a bike with a few tires down a hill and compared times, or rode it with a Power Meter around a test track, as we did?
I think there are many answers. One is that the engineers at big companies continually must develop new products, and have little time for basic research and thinking outside the box. There was no reason for them to doubt their lab test results…and nobody whose job it is to question things that are accepted as common knowledge.
The other thing is that our testing is actually more sophisticated than it seems. To get controlled conditions we needed days without wind and without jumps in temperature. This meant choosing test days very carefully, and more than half the time, there was a light wind anyhow, and we had to go home. If all this had been billable time, it would have been very expensive (and frustrating to explain to your supervisors).
So in the end, it’s perhaps wrong to expect break-through innovations from the big companies. It’s the same in cars: Tiny companies like Lotus make the best-handling cars, when you’d expect the big makers, with all their engineers and computing power, to easily out-engineer them.

February 22, 2018 at 6:48 pm
• Jan, thanks for the reply! Highly appreciated.
Please keep in mind: I really like your work and the Compass tires. I’m just not always convinced by your attempts to explain something based on Physics 😉
First of all: I am convinvced, that if profiles – that is reducing contact surface – make your bike tire grip better, you should use a softer rubber compound (and eliminate the profile). By doing so you increase the contact surface (no profile) and the interlocking should ovecompensate the profile effect.
Then: The reason why the big manufactureres offered narrow tires to road bikers is IMO easy: Blowing against the wind makes no sense for them. They offer what everybody wants. But I (kind of) trust them when it comes to optimising their rubber compound.
And one last honest comment: I do not think that a tire manufacturer riding a bike around a corner is to be considered a “neutral and repeatable” test. But as an engineer I am convinced that coming up with a semi-scientific grip test would be quite easy.

February 24, 2018 at 2:21 am
• The reason why the big manufactureres offered narrow tires to road bikers is IMO easy: Blowing against the wind makes no sense for them. They offer what everybody wants.

Are you implying the the big makers always knew that wider tires can be as fast? That they put out web site showing that higher pressures roll faster only to deceive customers? Perhaps they even paid pro racers ‘hush money’ to ride narrow 23 mm tires, when everybody knew that 25s would be faster? That would be a huge conspiracy!
I think the truth is simply that they believed their lab tests on steel drums that showed higher pressures to roll so much faster that narrow tires – the only ones you can make supple and withstand high pressures – had to be faster.
The same probably applies to tire tread patterns. As you mention, they put too much faith in ‘easily repeatable’ tests, rather than riding bikes and looking at what seems to work best and then designing tests to confirm or reject their hypotheses.

But I (kind of) trust them when it comes to optimising their rubber compound.

So do I – that is why we are working with Panaracer, one of the best tire makers in the world, and use the best rubber compounds that they’ve developed.

February 24, 2018 at 8:30 am
• Jan, to be honest: I doubt the big mafufacturers ever really tried anything different than the norm. Why should they – convince their customers that there were better products than the ones offered at the moment?

February 24, 2018 at 1:31 pm
• There’s another aspect of the cornering force that hasn’t been raised and that is the structural properties of the rubber contacting the road. When loaded in shear (i.e. sideways) rubber (or any material for that matter) eventually fails. If the total force needed to corner exceeds the structural ability of the rubber to transmit that force, the rubber will fail and the tire will skid/slip. A tire with a large contact patch distributes the force through more rubber and thus is able transmit more force. Note that this limitation is in addition to any limitations at the tire/road interface – whichever fails first will dominate performance.

February 22, 2018 at 11:47 am
• Great article. Keep up the good work! I have never been too concerned about traction as I stay primarily on good pavement. However, I am cheap and I am always interested in the longevity of tires. Sounds like you might have the best of both worlds: “the grippiest, yet long-wearing, rubber in the tire business.”

February 22, 2018 at 1:29 pm
• Rubber compounds over the last decade or so have made huge progress. It used to be that you could either have grippy tires (like the Michelin Hi Lite) that lasted <1000 miles, or hard rubber tires that wore like iron, but sometimes skipped sideways as you pedaled around corners. Now we can have both. And with wider tires, the wear is distributed over a much larger area, so they last much longer. Most riders get about 5000 miles out of a 42 mm tire, which makes the cost-per-mile of a high-end tire quite affordable.

February 22, 2018 at 6:59 pm
• Are you suggesting (gasp) that Sheldon may have been incorrect?
One factor that differs between two wheels and four is the camber of the tire. Cars (and especially racing variants) try to maintain the wheel at close to perpendicular to the road surface. That way, the relatively wide profile remains flat on the road when cornering. This can never happen with a two-wheeled vehicle.
I’m not convinced regarding the effectiveness (or not) of any fine tread pattern – road surfaces are just too variable, not to mention rubber compounds (from rock hard to gummy). It’s probably at least 50% compound, mixed with style and some hysteresis.

February 22, 2018 at 1:50 pm
• If you could ride a set of our tires with tread, and then a shaved set without tread (everything else the same), you’d probably notice the difference. I agree that having the right rubber compounds is just as important, but to get the best performance, we are optimizing all aspects rather than focusing on just one.
You are right that the road surface is random. That is why you need as many ribs as possible, so that as many as possible (but not all) will hook up. At the same time, the ribs need to be stiff enough not to squirm under cornering…

February 22, 2018 at 7:02 pm
• RickH

Good in theory but I’m not convinced. I’ve ridden tires with and without a “file” tread and have not noticed any handling difference.

February 22, 2018 at 1:52 pm
• As I mentioned above, if you could ride the same tire with tread and as a slick – eliminating other variables like rubber compound and sidewall stiffness (stiffer sidewalls give less grip, because the contact patch is smaller) – you’d probably notice the difference.

February 22, 2018 at 7:03 pm
• DaveS

Jan,
The best test that I have been able to come up with is to compare a well worn compass tire to a brand new one. I ride enough to have worn out several compass tires over the years. I have noticed a difference when a new tire has been installed, but I cannot say definitively that the new tire grips better. There may be other factors at play here. A well worn tire will be more subtle which may grip better even though the rib has worn off, offsetting the advantage of the rib.
I’ll have to do a better comparison when the next time I replace my tires.
Do you have a better test?

February 26, 2018 at 8:02 am
• Even the well-worn tire will have its shoulder ribs intact – you don’t corner that often compared to going straight to wear them significantly. So the best test is to shave off the tread of a new tire, and then ride the two one after another. We’ve done that, and the difference was noticeable even in the dry.

February 26, 2018 at 8:41 am
• Jacob Musha

Rick, are you pushing your bike to the limit of adhesion in corners? Keep in mind that you will never notice a difference if you’re “just riding along.” Only when you find the point where the tires break free will you be able to tell. Unfortunately, this almost always causes a crash unless you’re a very good bike handler or are on a low traction surface (mud, snow, etc.)

February 23, 2018 at 6:26 am
• In your tire experiments have you ever tried adding siping to a tire? I think that the siping that places like Les Schwab cut into car tires would be really interesting on a bicycle tire. I’m not sure if the automotive machines could be reconfigured to cut a bicycle tire.
https://www.lesschwab.com/learn/article/performance-tire-siping

February 22, 2018 at 4:19 pm
• The only thing that annoys me about the file tread on my compass tires, is that sand seems to cling to the tread a little more. This creates a little mess when I bring my bike indoors.
I wonder if the fine cut siping could improve this issue over a fine file tread.

February 22, 2018 at 4:30 pm
• I am concerned that small debris would get stuck in the siping and then work their way into the tire until it causes a puncture. Perhaps we can make a brush roller that cleans your tires before you bring your bike inside!

February 22, 2018 at 7:10 pm
• Yes it think that could be a major risk with siping.
A brush would be cool. There are some pretty cool designs out there for wheelchairs.
https://youtu.be/FjZtid6PHGU
https://youtu.be/dsSLG3SXfMU

February 23, 2018 at 11:38 am
• Interesting explanation on the Les Schwab web site about siping you mention: “Tread blocks get their gripping power from the numerous sharp surrounding edges.” If that is the case, then a tread like the Compass tread would be even better for cars, too, except it probably would wear off too quickly. Fortunately, bicycles rarely do ‘burn-outs’!

February 22, 2018 at 7:07 pm
• Yes I think that is one reason siping is popular. They are not too deep to cause large sections of the tire to tear out, but they tires can siped multiple times as the tire wears.

February 23, 2018 at 11:37 am
• wrangle

I thought that was the case up until very recently, influenced by articles like this one: http://www.sheldonbrown.com/brandt/slicks.html

February 22, 2018 at 5:05 pm
• Mx

High performance car tires actually melt into the irregularities of the pavement. ( Each year, there are thousands of metric tonnes of car tires being worn down — where does all the rubber go?.. A substantial amount of it likely turns into CO2 under friction-induced heat. ) There is an extensive body of knowledge on this stuff now built up in the world of auto racing, and the regular auto tire design, but it’s not clear that the same ideas / physics apply to bicycle tires. In part because the latter operate in a different regime; the rotational speeds, the normal and the lateral forces are distributed quite differently. So, I would be careful about drawing analogies…
That said, one can design experiments to ferret out the answers, with sufficient attention to hidden variables. Sadly, the budgets / financial gains associated with bicycle tires simply don’t justify the costs that would involve. 🙂

February 22, 2018 at 9:11 pm
• I agree that car and bicycle tires are very different – hence their tread patterns should be different.
After testing many bikes (more than 70 to date, riding each for a few weeks and at least 200 miles), I have come to conclude that the best designs usually are designed (and often built) by those who ride them hard. Just like the best cars are designed by people who can take them to the limit.

February 22, 2018 at 9:18 pm
• On the other hand, it’s much easier for normal people to take cars to the limit. I’ve pushed my Lotus to its limits and beyond (on a race track, not on the street), but you won’t find me doing that on a bike, I’m just not good enough to play in that regime of performance.

February 23, 2018 at 11:48 am
• On pavement, the transition from grip to skid is too abrupt to recover on most two-wheelers, but on gravel, mud and snow, the limits are much more approachable. Learning what it feels like when the bike is about to lose grip is something to learn on loose surfaces and then apply to pavement.

February 23, 2018 at 12:01 pm
• (On the limits of adhesion thread… I really need to get a life!)
Agreed re: playing in the soft stuff, it’s possible to recover. I’ve been learning that the last couple days playing in our unexpected dump of snow, low speeds loose surfaces, the front and rear wheels are flying all over, what a ball! It’s so much fun, I’m going to head out and do it again – running errands on a bike is something I look forward to especially

February 23, 2018 at 12:11 pm
• marmotte27

The file tread on the Compass tires does wear away in part. On my Loup Loup Pass, only the outer part of the chevrons still remains.

February 23, 2018 at 1:31 am
• You probably run the tires at a bit lower pressure than we intended. The longitudinal ribs in the center are the part that we intend to wear (mostly). In any case, it’s the outer part of the chevrons that is the most important. It may be time to replace your tires soon, though.;-)

February 23, 2018 at 7:17 am
• Frank Toman

Hi Jan.
If I only had one babyshoe tyre (because the other met an unfortunate end) … would you run it on the front or back? I’m guessing the back, where its supple fast rolling characteristics would be most advantageous.
Best. Frank

February 23, 2018 at 1:07 pm
• I would advise against running mis-matched tires on the same bike, because the cornering grip will be different on the front and the rear, which will give you weird messages as you lean the bike. If you are only concerned about comfort, then I’d say it depends on whether you have more issues with your hands, arms and shoulders, or whether you suffer from more seat problems…

February 23, 2018 at 1:47 pm
• Marco O.

If it’s the grippier tire of the two, you should definitely run it on the front. On a bike, losing the grip on the front tire is much more dangerous than losing it on the rear.

February 23, 2018 at 3:19 pm
• In my experience, whether you lose grip on the front or rear matters little. Only once did I recover a rear-wheel slide on a dry road, and then the wheel collapsed from the side load for which it wasn’t designed, and I crashed anyhow.

February 23, 2018 at 4:43 pm
• Marco O.

In my experience, losing the front tire always results in a fall, whereas losing the rear tire is much more manageable. When you brake, if you lock the front tire you will fall 99% of time, if you lock the rear tire, you will probably keep control of the bike. When I brake at the limit, I always make sure that the tire closest to losing grip is the rear one, not the front one.

February 24, 2018 at 3:26 am
• When braking, you are (hopefully) riding in a straight line. In that scenario, you balance the bike by moving the front tire from side to side. If you lose traction, you lose the ability to balance, which can cause a crash. Or more likely, the bike wasn’t perfectly upright, and the slide unbalances it by moving the front wheel in the ‘wrong’ direction. (If your bike is perfectly upright, a short loss of traction on the front will not cause a crash, as you can demonstrate on gravel.)
If you lose traction on the rear in a straight line, the unbalancing of the bike is comparatively minor, and you can still balance the bike by steering the front wheel from side to side.
When you corner, both tires contribute roughly the same toward keeping the bike upright. Then it doesn’t matter which tire loses traction – you’ll probably crash all the same.

February 24, 2018 at 8:18 am
• Marco O.

Negative. When turning, I can lose traction on the rear tire and still have the chance of saving the situation and avoid the fall. If I lose traction on the front tire instead (while turning), there’s not the slightest chance that I can avoid the fall. I remember all the times I used to lock and skid the rear tire just for fun. I couldn’t have done the same locking the front tire.

February 24, 2018 at 11:20 am
• Love the Batmobile. The standard 3.0 CSL is one of the most beautiful “glasshouse” cars of the 70s.

February 23, 2018 at 7:08 pm
• Hah! I identified the 3.0CS too. Can’t tell if it’s an L, but doesn’t matter since the hood and hatch lid certainly have been replaced.

February 23, 2018 at 8:30 pm
• Tom in MN

“pushed into the road surface with half as much force ” — careful, you mean pressure as the force is the fixed weight of bike and rider on the axle. And the pressure is basically the air pressure in the tire, so to get a larger contact patch you need to lower the tire pressure. Yes, physics say friction force is coefficient of friction times normal force, so only looking at the force you might think it would not be affected, but your whole hooking up argument with tread patterns is based on changing the coefficient of friction, which may also occur with changes in contact pressure that affect, for example, how well the tire conforms to the road surface. I suspect lower tire pressure would have helped with traction on that slick polished stone.

February 23, 2018 at 7:12 pm
• You are right – lower pressure gives way better traction, and I was riding 19 mm tires when I crashed on the polished stone. Still, I didn’t crash on the rougher aggregate of the road on those same tires…

February 23, 2018 at 8:18 pm
• The coefficient of friction between rubber and tarmac is sigmoidal. That means: For every rubber compound there is a sweet spot for pressure.
Pressure too high – decreased contact surface
Pressure too low – no interlocking, rubber too hard.
So this is what you do with rubber tires on tarmac: Increase the contact surface and at the same time use a softer rubber compound.

February 24, 2018 at 2:27 am
• It’s easy to overthink this. In my experience, lower pressures increase the contact patch so much that grip increases, but the ability of the sidewalls to transmit that grip to the rim decreases until the bike becomes unrideable.

February 24, 2018 at 11:50 am
• fnardone

> The center tread doesn’t matter much
Doesn’t it matter when braking ? Or maybe the forces are so larger than other factors come into play ?

February 24, 2018 at 1:04 am
• As you suggest, when braking hard, the entire weight of the rider is on the front wheel. This compresses the tire so much that the shoulder ribs will touch the ground. We haven’t tested it, but it’s likely that this aids with the braking traction as well.

February 24, 2018 at 8:09 am
When I was a child in Canada, it was common practice for bus companies to sipe the tread of bus tires in the autumn. They already had relatively aggressive tread patterns, but the siping gave extra grip in icy roads as the expense of accelerated wear.
I run Gravel Kings on a couple of bikes (tubeless – have punctured one on flint but it sealed well enough to get home). The funny thing is the tread pattern has an affinity for… gravel. Riding on canal paths in France, the size of the fines used for surfacing was just right to be picked up and fired into my fenders – a sotto machine gun effect. I doubt the exact tread pattern has much significance beyond cosmetic, but it does create a noise problem.
There is much accepted wisdom in the tire world that upon study, turns out to be not as predicted. I worked for a huge tire retailer in the 1970s, when radial tires started to become available. The recommendation was (and no doubt still is) to never mix tire types – all radial or all bias.
Many years later, Popular Mechanics did a practical test with professional drivers using several different cars – running with all radial, all bias and then mixing both ways (but always the same type on the same axle). The result was the cars were all fine, all the time. Never unsafe. The radial tires performed best (even on cars not “designed” for them) and the bias the worst (stopping distance, cornering speeds, wet braking, etc.). But in no configuration was the vehicle unsafe – just “different”.
And I have no doubt this is the same with bicycles and motorcycles. Mixing things up results in *different* handling. The only unsafe condition would be a rider assuming nothing was different when it actually might be quite different. And even then, most of us ride far below any such limits most of the time.
Most will be aware of the recommendation that if only buying two new car tires, they should be placed on the rear axle. This seems counterintuitive, as the newer tires would have greater hydroplaning resistance (a real issue for cars) and also considering the majority of cars are now front wheel drive.
But the rationale is that more-worn rear tires can exacerbate an oversteer (spin) condition, which the average driver cannot correct. A front wheel skid, by comparison (understeer) usually results in “plowing” off the road and is much more within the average driver’s ability (and the focus of safety features like airbags). So it is essentially a lawyer’s recommendation – the choice of perhaps accepting more minor accidents with a goal of fewer major accidents.

February 24, 2018 at 8:42 am
• I have some doubts about the Popular Mechanics test. It all depends on what you test. Similarly, Avocet once tested the grip of slick tires vs. treaded ones on a wet steel drum, and they found no difference. No wonder – on a smooth steel surface, there isn’t anything for the tread to interlock with!
I don’t want to go into too many details, but in a car, having less grip on one axle than the other can a) lead to one set of wheels locking up under breaking and b) one set of wheels losing grip before the other in cornering. In ‘normal’ driving, this may not be a problem, and that may be what Popular Mechanics tested, but it’s during emergency situations that you really need to rely on your car.

February 25, 2018 at 8:58 am
• A long time ago, in Road and Track (how did we ever get here from a bicycling blog..) I read the distinction between oversteer and understeer: in oversteer, the passenger wets their pants, while the driver wets their pants in understeer.

February 25, 2018 at 9:13 am
• Archetype

“In my experience, losing the front tire always results in a fall, whereas losing the rear tire is much more manageable. When you brake, if you lock the front tire you will fall 99% of time, if you lock the rear tire, you will probably keep control of the bike. When I brake at the limit, I always make sure that the tire closest to losing grip is the rear one, not the front one.”
Well stated. I have the lost the rear on a few occasions myself while just tipping in to a corner ( I typical trail brake at higher speeds) And each time have managed to save it. I would never think about using the front brake while cornering. If I’m braking hard before the entry point, I’m on the f&r, but when braking into the corner and up to the apex, I’m strictly on the rear. Also, in the rain, I mostly utilize rear braking. Controlling a slide is much easier in the rear than the front. Front will wash so quick there is no saving it. It would be down to mostly pure luck.

February 24, 2018 at 5:44 pm
• If you catch a rear slide while cornering on the limit, your rear wheel will probably collapse from the sudden side force as it regains traction. (Mine did the one and only time I caught a rear wheel slide.) Sliding the rear wheel during light cornering can be fun – we did it all the time as kids until our parents noticed that our rear tires were getting bald – and it’s easy to recover from that. It’s also a technique that is useful in cyclocross for very tight downhill turns.
The goal of ‘trail braking’ is to increase traction on the front wheel by braking as you start to turn. (This give the front tire more ‘bite’, reducing the slip between tire and road that always occurs, and thus makes the bike turn in more sharply.) This means you’ll have less traction on the rear – which is why trail braking always should be done on the front. If you can trail brake on the rear without locking up the wheel, it probably means that you aren’t braking hard enough to transfer much weight toward the front.
Front-wheel skids are problematic if the bike is leaning even just a bit. On a low-trail bike, which tends to stay more upright, locking up the front wheel briefly (meaning, split-second) while going straight on gravel isn’t a big deal. But if you are leaning sideways, as you mention, the front wheel washes out. In that situation (going ‘almost’ straight), a rear wheel skid is much easier to manage.

February 25, 2018 at 9:07 am
• then there’s this guy: https://www.youtube.com/watch?v=Y-z0Kh0pvNM
(feel free to kill this thread that has gone too far!)

February 25, 2018 at 9:23 am
• Archetype

I hear you. In some instances you may want to trail brake with the front but never alone in my experience. Both brakes or the rear brake. It depends on ones experience and riding style. I have a lot of trail braking experience from racing motorbikes Jan. On the pushbike I have apexed 90 degree corners at 40 mph many times and have had exit speeds at over 50. Too many variables to say it should be one single way. Too much disparity on rider experience and riding styles. In the end, it is what works best for the specific rider.

February 25, 2018 at 9:56 am
• Archetype

I meant to mention, I have locked the rear up on entry while trail braking on 3 occasions, and it was quite the experience! 😀 But I still prefer this method to using the front brake.

February 25, 2018 at 9:58 am
• Archetype

Also, there is little weight transfer on a pushbike (without suspension) compared to motorbikes and suspension bikes)
Therefore, front tire grip is not going to be similar in that respect. And I think there are many variables that go along with this as well. Tire width, pressures and rider weight. (when I was on the track, I would utilize the front more while trail braking)
But on the bicycle, it is easier to lose the front tire grip in my experience when pushing hard through a corner. (which I have done- not good!) So to this end, I try not to use the front too much.
I’ll brake hard with the front and the rear while mostly upright, then keep the rear trailing when carrying high corner entry speed. This helps me to ‘set’ the bike on the proper line, for a good exit.

February 25, 2018 at 10:12 am
• Also, there is little weight transfer on a pushbike (without suspension)

The photo below shows that if you brake hard enough, you can transfer 100% of the weight to the front wheel… That is also the reason why hard braking should be done only on the front. The rear brake is useful only when you cannot brake hard due to limited traction, and the weight transfer is much-reduced.

February 26, 2018 at 9:14 am
• Archetype

Good points Jan, But what works best for me is utilizing the rear brake more. It comes down to rider preference and style of riding. For most riders, I believe that using the front is wiser.

February 26, 2018 at 3:16 pm
• SteveP

The physics of the situation dictate that hard braking on two wheels will stand the bike up vertically as the forces balance, if traction is maintained. Of course, the front wheel/tire is dealing with most of the forces and may lose traction (skid out) instead. Motorcyclists even have names for the type of front-end wipeout “dump” you suffer – lowside (front wheel washes out) or highside (bike stands up and throws you over). I have had my motorcycle (which weighs over 600lb/275kg) lift its rear wheel similar to Jan in the photo above. Much more weight, possibly higher speed (F=MA) but with a much larger contact patch and double hydraulic disc brakes. Gets your attention.
MSF courses teach riders how to handle rear wheel locking and I never find it an issue on a bike or motorcycle. When we were kids we used to race our coaster-braked bikes downhill and see who could leave the longest skid mark. (On the pavement). Went through a lot of tires and tubes that way

February 26, 2018 at 1:17 pm
• Paul Hoffmann

Jan, do you usually set up your front brake with right lever, as on the photo above?

February 26, 2018 at 10:24 pm
• Felix Holub

Jan, does the direction of rotation matter for the effectiveness of the thread? Or is it pure cosmetics to have the arrow-shaped thread point to the front?

February 27, 2018 at 5:49 am
• The tread is not directional. All that matters is to get as many of the ribs as possible in contact with the road. They are angled so they don’t fold under the forces of cornering.

February 27, 2018 at 6:58 am