Optimizing Tire Tread

Optimizing Tire Tread

Most tire manufacturers agree that supple sidewalls and a thin tread make a tire fast, but the role of the tread pattern remains poorly understood. Most modern tires have either a completely smooth tread (slicks) or a coarse tread pattern similar to car tires. Many high-performance tires are smooth with just a few large sipes. None of these tread patterns are optimized.
Car tires have tread mostly to prevent hydroplaning. With their wide, square profile, a layer of water can form between tire and road surface. The tread pattern forms channels so the water can be pushed out of the tire/road interface.
Bicycle tires do not hydroplane. Their contact patch is too small and too round for that. This means that car-inspired tread patterns are not necessary on bicycle tires. Does this mean that no tread pattern at all – a slick tire – is best? Any tread pattern reduces the amount of rubber on the road surface… In the lab, it does work that way: Slick tires grip best on smooth steel drums.
Real roads are not as smooth as steel drums. An optimized tire tread interlocks with the irregularities of the road surface to provide more grip than the pure friction between asphalt and rubber. This is especially noticeable in wet conditions, when the coefficient of friction is reduced by half, yet you can corner with about 70-80% of the speed you use on dry roads. (Unless the road surface is greasy…)
The ideal tire tread has as many interlocking points with the road surface as possible. The “file tread” found on many classic racing tires does this. The ribs are angled so they don’t deflect under the loads of cornering or braking.
Why do race cars use slick tires, and not a file tread? The reason is simple: It would be abraded the first time the car accelerates. However, bicycle tires don’t wear significantly on their shoulders – the part that touches the ground when you corner hard – so we can use a tread pattern that is optimized for grip without worrying about wear.
Each Compass tires has three distinct tread patterns, each designed for a specific purpose.

  • Center: Fine ribs serve as wear indicators. When the lines disappear, the tire is about half-worn. (The tread of our narrower tires is not wide enough for ribs, so small dots are used instead.)
  • Shoulders: When the bike leans over as you corner, the tire rolls on it shoulders. A chevron or “fine file” tread pattern optimized grip.
  • Edges: This part never touches the road (unless you crash). They serve only to protect the casing from punctures, so they don’t need any tread.

Supple casings make tires faster, but a supple casing is of little use when it’s covered by thick tread rubber. The fastest tire would have just a minimal layer of tread rubber, and many “event” tires are made that way. Unfortunately, that means that they don’t have much rubber to wear down until they are too thin to use. At Compass Bicycles, we call these tires “pre-worn”.
Compass tires have a slightly thicker tread in the center. A little more material there doubles or even triples the life of your tire, while adding minimal weight and resistance. (On our widest 650B x 42 mm tire, the added tread weighs less than 50 grams.) Once you have ridden the tires for a few thousand miles, they’ll be as light as the “event tires”.
On the shoulders and edges, the tread does not wear. So we made it much thinner to keep the tire supple and reduce its weight. The tread extends far enough down the sidewall that the casing is protect when seen from above. Extending the tread further adds little protection, but makes the tire less supple and thus less comfortable and slower.
Another important factor is the tread rubber. This is an area where incredible progress has been made in recent decades. In the past, you could either have good grip or good durability. I used to ride Michelin’s Hi-Lite tires, which gripped well, but rarely lasted even 1000 miles (1600 km).
Compass tires use Panaracer’s best tread rubber, which is amazing. Our tires are among the grippiest you can find, yet I just got an e-mail from a 230-pound rider who got 3786 miles (6093 km) out of a set of our 26 mm-wide Cayuse Pass tires. The wider tires spread the wear over more rubber, so they last significantly longer. (Don’t try to set wear records, but replace your tires once they get thin. The risk of flats, or worse, blowouts, is not worth getting an extra few hundred miles out of a worn tire.)
Tread color is another important consideration. Modern colored treads no longer are the “death traps” they used to be, but especially in wet conditions, the grip of tires with colored treads – including the Grand Bois Hetres we sell – is not quite as good as that of black treads. That is why we offer only black tread.
Click here for more information about Compass tires.
Update 9/25/14: Roadbikerider.com just published a review of the Compass tires. Click here to read it.

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Comments (54)

  • Harald

    Did you experimentally test your hypothesis about a file tread improving cornering performance? I know that the German “tour” magazine does experimental cornering tests with their scooter rig (http://www.tour-magazin.de/technik/test_center/komponenten/reifen/reifentest-tour-nasshaftung/a10453.html). It would be interesting to see how otherwise identical tires with no tread/file tread (and maybe other possible tread patterns) would do in such a test.

    September 25, 2014 at 7:53 am
    • Jan Heine, Editor, Bicycle Quarterly

      I remember the scooter test – they used a stuntman who cornered on tighter and tighter radii until he crashed… As I recall, the results were inconclusive.
      In our real-road experience, slick tires don’t grip well in the wet. I had three crashes in corners during the last decade, and two were on slick tires. One was on a shaved set of Grand Bois Hetres (with the tread pattern removed), which surprised me when they seemed to grip a lot less than the normal version with the tread intact.
      Regarding the better grip of the file tread compared to other treads, when you try our tires, you’ll notice it. You really have to recalibrate your inputs, since they corner on a tighter radius. The first time I rode them, I almost went into the curb on the first corner. (All tires slip a little as you corner, some just slip more than others. The slipping only becomes a problem when it suddenly gets so great that you slide sideways and crash.)

      September 25, 2014 at 8:18 am
  • doug

    I have been using a set of all-black Cypress EL since June. They are definitely the best tires I have used by far. They have a bit over 1500 miles (rotated at 1000 miles) and definitely show some wear, though the ribs are still visible on both tires (I’m about 220 pounds). There are also some cut threads in the casing that I had to boot due to a series of hashed tubes that began leaking.
    For most of their use I only had two flat tires, which is a pretty good rate in my opinion. However, the recent rain resulted in my getting two flats in two days, which is definitely annoying, but I hope that the summer’s worth of debris will be washed off the road in the next few days.
    I do have a question: how does the Cypress EL compare to the Stampede Pass in terms of tread thickness, etc.?

    September 25, 2014 at 8:16 am
    • Jan Heine, Editor, Bicycle Quarterly

      The Stampede Pass has the same tread thickness in the center as the Grand Bois Cyprès. The tread on the shoulders, where it doesn’t wear, is a little bit thinner.

      September 25, 2014 at 8:22 am
  • Sree

    I think Brandt put it well when he wrote “Tread patterns have no effect on surfaces in which they leave no impression”. Assuming tread patterns have an effect on real roads, have you found they improve traction significantly over a slick tire? Does this improved traction come at the cost of a significant increase in rolling resistance over a slick tire?
    If you’ve done a detailed study, I’d like to read more. Thanks!

    September 25, 2014 at 8:27 am
    • Jan Heine, Editor, Bicycle Quarterly

      Brandt was incorrect in this case. Michelin studied this in the 1980s, and published the results in the Bike Tech newsletter. Car slick tires are so soft that the road just digs into the tire, and you don’t need tread. But they also wear out in 100 miles or less.
      Bike tires can interlock and do interlock with the road. Think about riding on asphalt vs. steel panels that cover holes in the road during construction, in the dry and in the wet.
      Asphalt: Wet cornering speed about 70-80% of dry cornering speed.
      Steel: Wet cornering speed about 30-40% of dry cornering speed.
      The reason you can corner so well on wet asphalt is that the tire interlocks with the road surface. On steel, it doesn’t, and you only have the (much-reduced) coefficient of friction to provide cornering traction.

      September 25, 2014 at 8:35 am
      • Sree

        I don’t think Brandt was wrong about this particular statement. Tread patterns increase surface area which would theoretically increase interlock. The easiest way to verify that interlock has increased is to see if an impression was left on the surface as the tread “dug” into the surface — even if it was microscopic.
        Your statement about wet asphalt vs steel does prove that road and steel behave differently, but my question was really about slick tires vs tires with tread patterns on the same surface. That is, does having a tread pattern improve traction (significantly) on wet steel panels over slicks?
        Thanks for the reference to those tests, let me see if I can find the article.

        September 25, 2014 at 9:05 am
        • Jan Heine, Editor, Bicycle Quarterly

          You don’t need to make an impression on the road surface to interlock. Think of two cogs meshing, they don’t need to leave impressions on each other to mesh.
          On the steel panel, no tread pattern (expcept perhaps suction cups) makes a difference, because there isn’t anything to interlock. It’s like trying to mesh a cog with a steel disc…
          On the road, I can definitely say that the Compass tires have more traction – wet and dry – than a shaved set of Grand Bois Hetre tires that are slick. Apart from the tread pattern, they are identical – same casing, same tread rubber, same width, same pressure, same bike. Interestingly, when Specialized recently asked professional racers whether they wanted slick tires, they apparently preferred a file tread, too.

          September 25, 2014 at 9:18 am
          • Sree

            You’re right about the cogs and I wasn’t aware that a similar effect exists on real roads and could improve traction. I am still surprised about the significance of such an “interlock effect” on real roads. However, your comparison with the Grand Bois Hetre (and your reply to Harald above about the grip of slick tires) are what I was looking for. They convince me, and I look forward to reading more about the other interesting questions you investigate.

            September 25, 2014 at 9:36 am
  • Harth Huffman

    Well, the Stampede Pass (32mm) version earned a very strong review in the Road Bike Rider newsletter this morning, so you are doing something right! Plus, I love my Gran Bois 28mm tires.
    Nice work, Jan.

    September 25, 2014 at 8:39 am
    • Doug

      “I weigh about 150 pounds and run 25s at 100 psi but inflated these 32s to only around 80 psi. I could probably go lower.”
      Yea, he could go lower nice got 70 pounds in this guy and I run my extra leger 32s at 80psi with zero issues.
      I’m not surprised that he’s running such high pressure; most cyclists are psychologically incapable of running their tires at appropriate pressures

      September 25, 2014 at 8:48 pm
  • Chris

    I’d still like to see some good data on treaded vs. smooth tires when cornering on asphalt. As we all know, our perceptions about what works best, even with significant experience apparently backing them up, aren’t always correct.
    Professional racers still seem to prefer tires that are too narrow and inflated to way too much pressure (you’ve convinced me on these points, Jan!), so I don’t give much credit at this point to their tread preferences even though they have far more experience than I when it comes to cornering adhesion limits.
    And no, I won’t be the one volunteering to see how fast and tight I can turn until I crash. But I’d sure like to read the statistically valid results of such a test in BQ.

    September 25, 2014 at 10:33 am
    • Jan Heine, Editor, Bicycle Quarterly

      It’s very difficult to quantify cornering adhesion on a two-wheeler. (In a car, you just drive around a skidpad until you break traction.)
      I place more trust in the on-the-road experience, especially since there isn’t a placebo at work like with the narrow tires (which feel faster without being so). I cannot imagine a tire that feels like it corners poorly, yet corners well, or vice versa. So when riders (professional and others) consistently have reported over decades and on several continents that slick tires don’t grip well in the rain, there probably is something to it.
      Of course, tread rubber also plays a role, but I don’t see why the tires with traditional tread patterns (many like FMB made by small companies without access to the latest and best rubber compounds) would have more grippy rubber than the slicks from the big makers.

      September 25, 2014 at 11:51 am
      • Fred Blasdel

        It’s a perfectly normal design conceit for a high end MTB tire for loose conditions to “feel like it corners poorly, yet corner well” because the transition knobs between the center tread and the edging knobs have been omitted. The large gap means that if you roll the bike over gradually without confidence it’ll feel like garbage and you’ll washout if you don’t fully commit. However if you properly lean the bike underneath you the tire can deliver absurd ultimate traction, because there are no transition knobs to unweight the corner knobs.
        The converse is very common in “file tread” cyclocross tires, most designs have awfully counterproductive corner knobs. They’re too small and unsupported to hold your weight alone so they feel grippy as you transition and then break loose instantly. They’re more transparently bad on roads even unpaved ones, where they get extremely squirrely the moment you lean far enough for the knobs to touch at all.

        September 26, 2014 at 2:44 pm
        • Jan Heine, Editor, Bicycle Quarterly

          I hadn’t thought of knobby tires. The scenarios you describe make sense. I am lucky that I’ve always raced cyclocross on good tires, so I haven’t experienced those issues.

          September 26, 2014 at 6:34 pm
  • Rick Harker

    I have posed this question to many retailers of “high end” bicycles and equipment. The best description came from the Aussie Vittoria representative. In a perfect world no tread is needed on a bicycle. However, on roads that are less than perfect a fine imperfection of smooth tread is better in more than one way. One of these is the instance of very fine dust/dirt layers on the road act as a dry lubricant composed of tiny movable particles when your tire rolls over them with some lateral load. The small file sized sipes in the tyres help to push through this and offer better grip.
    My own real world tests cannot determine this as I’m not that brave but… My first use of Grand Bois tires had me comparing tires and pressures on a small bike path. It dropped 4 metres over 50metres and roughly level after that. I varied pressures between 45psi and 90psi that yielded interesting results. 90psi “felt” supremely faster. By this the bike felt lighter in the steering and surely faster, I thought. Did it? Yes! I averaged 2 metres more over 330 metres. Comfort factor? Roughly 30% less. Worth it? NO!
    I did the same with 23mm tires (Micheline pro 4 service course) at various pressures from 80psi to 120 psi. Results were the same as the 30mm Grand Boise except I felt every bit of the road and the distance travelled didn’t change between 90psi and 120psi.
    I’m sticking with what I have personally found and this reflects what Jan already knows.
    Thanks Jan.

    September 25, 2014 at 6:44 pm
    • Jan Heine, Editor, Bicycle Quarterly

      Panaracer believes that a little tread also makes the tire faster, since it allows the tire to conform to very small surface irregularities, thus reducing suspension losses. Since nobody has tested this on real roads, it’s hard to know.

      September 25, 2014 at 7:01 pm
      • Rick Harker

        The Vittoria rep said a similar thing about the softer race tires. I’m sure the major tire manufacturers have some information they won’t share but production for the masses will have some trade offs. There are some tires that have no protection and are undoubtedly faster for the pro racers but also they have a team car following too.

        September 25, 2014 at 7:28 pm
        • Jan Heine, Editor, Bicycle Quarterly

          The beauty of wide tires is that many of the trade-offs disappear. You don’t need flat protection (which makes the tires harsh and slow), because the tires are run at such low pressures that they just roll over debris. (In 18,500 km on my René Herse, I’ve had 3 flats with Grand Bois and Compass tires, all from steel wires.) They roll as fast as narrower tires, but offer more speed, and no risk of pinch flats.

          September 25, 2014 at 7:45 pm
      • Oscar Dube

        Dear fellows,
        I would like to enter the discussion at that point to defend the view that on hard surfaces no tread is needed at all. Here are some arguments of interest:
        First, the irregularities of a road are random, while the tread is not. Even if it was, it could never “match” the irregularities of any road, thus it can’t improve grip. Even worse, theoretically it should lead to less contact area. The whole thing only works because no tire can be pumped as hard as to deform the road, so the road deforms the “tread pattern” (in our case we should call it “ornament”), at least as long as it isn’t too deep (“studded”). Interlocking occurs because the tread is SOFT, and the more tread there is to be penetrated by the pavement, the more grip you have, period. That is the obvious one.
        Second, what is less obvious is all the bogus manufacturers and distributors of tires tell to people in that area where so much room for “feel” and “experience” its left. Vittoria sells tires with tiny tread patterns, so they tell you it’s good. Frankly, Jan, you do the same.
        Third, to enter the battle of anecdotical evidence: I ride fast and (by purpose) with purely slick tires only on any surface. They range from 25 mm with to 45, depending on the bike. I also do regularly experiment about how tight i can turn until i crash or how hard I can brake, just for fun, and regularly ride in the rain. So I did some research for you (and yes I did fell) and the picture is rather clear: tire with always means something, but tread patterns only off road (and even there, they are only just as important as width). Chemical composition of the tread also has effects you can experience in every day riding. My favorite example are coniferous forest trails where the needles are packed so densely (often by lumber work) that they practically form am smooth surface and you can easily ride your 30+ km/h without any hazard. Maybe tread would help theoretically, but do you need it at that point?
        Last point: if a tiny tread had any effect, it would lose it after about 1000 km. In that case, I would have to buy 5 times or so more tires a year than I actually do to stay with “top performance”. I would be a very good consumer.
        Until now I did liked pretty every thing on this blog, but this really is to much wishful thinking (because you like the look of herringbone?).
        The test Tour made are probably the best up to now, but it’s design still left room for experimental bias. Mr. Brandt put it right once and for all (in that case) and he even recommended to use wider (slick) tires if traction is an issue (on hard surfaces). Good logic makes a lot of experiments unnecessary.
        Sincerely yours

        September 26, 2014 at 12:40 am
        • Jan Heine, Editor, Bicycle Quarterly

          Thank you for summarizing the argument for slick tires so well. This is what I used to believe, too, before I had much experience riding with many different tires. To your points:

          First, the irregularities of a road are random, while the tread is not.

          They don’t need to match up perfectly to interlock. Drag a piece of coarsesandpaper across the road, then a piece of cardboard. The sandpaper will interlock with the surface irregularities, even though they don’t match perfectly. For the tire, the more ribs you have, the more grip you get.

          Second, what is less obvious is all the bogus manufacturers and distributors of tires tell to people in that area where so much room for “feel” and “experience” its left.

          Feel and experience are much better than theoretical reasoning. Just think of flexible fork blades, where the “experts” told us for years that only the steerer tube flexed, until we demonstrated that fork blades also can flex significantly. To say nothing about the argument that higher tire pressures roll faster, which those same “experts” defended for the longest of times (and perhaps still do).

          Third, […] I also do regularly experiment about how tight i can turn until i crash

          Be careful! I wouldn’t crash on purpose – unless you do it as a very controlled experiment, it doesn’t advance science, and you might get hurt.

          Last point: if a tiny tread had any effect, it would lose it after about 1000 km.

          That applies only to the center of the tread – which is why we call that portion a wear indicator. The shoulders don’t wear significantly, even if you corner hard and ride mostly on sinuous mountain roads. Look at a worn-out tire – the tread on the shoulders is completely intact.

          Mr. Brandt put it right once and for all […]. Good logic makes a lot of experiments unnecessary.

          Jobst Brandt’s strength was good logic, and he has contributed greatly to the science of cycling. However, good logic only can generate hypotheses, and those must be tested in the field. Some of Jobst’s hypotheses have held up well (the need for high spoke tensions to build stronger wheels), but other have not (the need of high tire pressures to roll fast). Based on my experience, I think that tire tread falls in the latter category.

          September 26, 2014 at 5:45 am
        • Sree

          While Jan’s evidence is indeed anecdotal, it is of high quality — note the comparison with Hetre’s which were nearly similar. Of course, a controlled experiment in the lab could confirm (or disprove) the effect of tread patterns on cornering, but I am not sure how a representative piece of road could be replicated in the lab. Etched steel cylinders, maybe?
          As for the theory of interlock, it’s fairly qualitative as presented here. For example, it is not clear why the file tread pattern is what Jan chose, and not a random sand-paper-like pattern. Other questions like how deep should the tread pattern be for this interlocking to occur also arise.
          And then there is the engineer’s question of how much does it really matter? Jan’s experience seems to suggest significant gains, so these are probably not just academic questions.
          (P.S.: I haven’t interacted with Brandt, but from his writings it’s hard to pigeonhole him as a logician/philosopher. He was no stranger to experiment, and as that photo of his shows, he did explore this particular subject experimentally.)

          September 26, 2014 at 7:45 am
          • Jan Heine, Editor, Bicycle Quarterly

            it is not clear why the file tread pattern is what Jan chose, and not a random sand-paper-like pattern.

            A sandpaper-like pattern wouldn’t work well in rubber: The little knobs would just flex. The chevrons of the “file tread” provide a more rigid pattern.

            September 26, 2014 at 8:06 am
      • Harald

        So here’s an idea for an experimental design:Take two tires with a center file tread (or whatever pattern you want to test) and without on the rear wheel of a bike and do brake tests. Measure the deceleration at the point just before the tire starts skidding. Because of the shifting in weight etc. it will be somewhat difficult to control all the variables, but in principle this should show if the tread increases adhesion or not. Given Jan’s experience, the difference should be large enough to be measurable with statistical significance. Thoughts?

        September 26, 2014 at 10:11 am
        • Jan Heine, Editor, Bicycle Quarterly

          Apart from the problem that there are no tires with a center file tread, getting repeatable results with this method would be hard. It might be easier to drag the tire across the road surface at an angle and measure the force required, but that also isn’t a meaningful test. After all, when the tire slides, you already are crashing. What we care about is the grip while the tire slips imperceptibly during normal cornering. TOUR has tried in various ways to measure this, and even with considerable effort, they have come up empty-handed. It seems the best we can do is ride tires and compare how they corner…

          September 26, 2014 at 10:25 am
  • Mitch

    Hi Jan,
    I wanted to point out that when the coefficient of friction is reduced by half, you’d expect to corner at 71% of your original speed. Velocity is a squared term in the equation for centripetal acceleration, so when the coefficient of friction is cut by 1/2, velocity drops by 1/sqrt(2). Your experience of wet cornering at 70-80% of your dry speed seems more-or-less consistent with the drop in the coefficient of friction.
    That said, I have no idea if file tread patterns are optimized or if slicks perform equally well in the wet. There are so many variables on open roads it’s difficult to draw a conclusion. My subjective assessment is that having tread helps in limited traction situations, such as in the wet or when there’s sand on the road. The bike feels more controllable as it loses and regains traction, and I feel more confident riding fast with tread in those situations. Life is too short to ride tires you don’t like. It’s obvious that you and many others like the tires you have made by Panaracer, so congratulations on that. And thanks for your contributions to cycling.

    September 25, 2014 at 7:14 pm
    • Jan Heine, Editor, Bicycle Quarterly

      Thank you for clarifying the speed. The fact that traction is decreased much more on wet steel plates (compared to dry ones) than on wet pavement seems to indicate that some interlocking does occur.

      September 25, 2014 at 7:42 pm
  • don compton

    Got my 700×32 tires in the mail yesterday. I installed them last night. I rode today after the rain quit( I live in Lodi,Ca. and we don’t ride in the rain). The tires are the next step up from my Grand Bois 700×28’s. I tried them on both my Roadeo and my Hampsten SBTI. They do not feel heavy on the bike and the ride is so good that you want to challenge the bumps.

    September 25, 2014 at 7:52 pm
  • B. Carfree

    Although this is not quite on topic, I have ridden just under 3500 miles on a set of Compass 26 X 1 3/4 tires on my tandem (325 pound team; 190 pound stoker). About a fourth of those miles were fully loaded touring and another few hundred were on gravel. The front tire still has at least two thousand miles in it if I left it there. The rear looks to have another thousand to fifteen hundred (at which time the front tire will move to the rear). One flat so far; of course it was from a steel wire.
    The $25 tires that I replaced with the Compass tires only lasted about 1500 miles, so the Compass 26″ tires are a much better deal in terms of pennies per mile. Of course, after our first ride with them my captain fell in love with them and it felt like the roads had all been repaired from the stoker’s saddle.
    Faster, more comfortable, better mileage, less expensive, what’s not to love? Thanks for all the development efforts and for getting the word out here in so many interesting ways so that people can enjoy the benefits of your work.

    September 25, 2014 at 9:22 pm
  • Oscar Dube

    With regard to my comment above: I also forget to add: it is NOT TRUE that the edges of the tread do not touch the road. They do, if you corner correctly (or “hard”, as some say to brag). They do it even more, as the tire deforms under weight and brigs that area in contact with road debris or earth, if you ride unpaved paths.
    I have still going on a thing with conti because they recent generation of standard GP tires has a stupid “smooth transition” from casing to tread that came out to short & thin on large parts of the tire.
    Exactly where the post says there is no contact, on my old conti GPs you clearly see long stripes of abrasion through the ridiculous thin tread an then the casing. About 4 700×28 tires where ruined that way in just a few weeks.

    September 26, 2014 at 12:53 am
    • Jan Heine, Editor, Bicycle Quarterly

      If you corner so hard that the tire rolls on the unprotected casing, have a friend take a photo or a video. All of us would enjoy watching it.
      The tire deformation during hard cornering works the other way – it brings the center of the tread back under the rider. However, for good cornering, tires shouldn’t deform a huge amount. When they do, it reduces the cornering speed as the tires break traction, then regain it, then break again… That is why we run tires at relatively high pressures compared to cars and motorbikes. (Another reason is that supple tires aren’t held up by their sidewalls, whereas car and motorcycle tires have much stiffer sidewalls.)

      September 26, 2014 at 5:51 am
      • Oscar Dube

        Dear Jan,
        you got it wrong, but maybe I wasn’t clear: I did not roll on the (sidewall) casing, but on the section of the tread you claim does not contact the road (and hence may be smooth, as the picture above the post shows…).
        My example was tires that were manufactured badly, so that that the tread in that same area was rubbed away after a few day of riding, exposing lot of casing were it should not (quote myself “.. an then casing” i. e. the casing where tread should have been). QED you ride on the smooth edges of the tire. If you are interested in that, I can offer plenty of photos showing the damage. Just put a set triangle over the picture of your tire tread; these smooth sections move to the contact point already with some 30°, that’s not magic. True, the tire deforms, but after all it can not twist around like a worm, keeping its belly down.
        The purpose of picking that point was the fact that this section of your tires is smooth, yet it provides grip in the most crucial moment, when you corner tightly.

        September 26, 2014 at 8:02 am
        • Jan Heine, Editor, Bicycle Quarterly

          I still doubt you corner on that narrow strip right next to the unprotected casing. Of course, it depends on the tire, too – maybe there are some tires where the tread doesn’t extend far enough.
          I looked at my tires, but since that part of the casing does touch the ground when riding in soft gravel, I cannot tell whether it has touched the ground during cornering. On the other side, if it did, you’d expect a very sudden breakaway at the limit, and that certainly doesn’t happen with our tires.

          September 26, 2014 at 10:22 am
      • Fred Blasdel

        I have unmistakably cornered on that narrow strip of smooth tread at least a few times on your Babyshoe Pass tires
        I had a lowside crash on them one night in June speeding down Interlaken where I had a *very* sudden loss of traction leaning the bike over and put a quarter-sized hole in my elbow through several layers of clothing.
        At the time I was also skeptical that I’d reached that lean angle, but a month ago I got my first flat on the tires — a small glass cut right in the middle of that smooth strip of tread.

        September 26, 2014 at 1:59 pm
        • Jan Heine, Editor, Bicycle Quarterly

          Interesting observation. Sudden loss of traction can be lots of stuff, like oil residue on the road, and the small cut could have occurred next to the part you actually ride on… but this one is something we can actually test. Maybe high-speed photography while you ride that corner, or rubbing something on the tire and seeing where it rubs off…

          September 26, 2014 at 6:33 pm
  • marmotte27

    For the last year I have had slick tires on my bike, and I have crashed twice since while cornering, one crash sending me to hospital… my only other crash in ten years before had nothing to do with tread (but with width, when my 23mm tire got caught in a crack between to paving stones). I wouldn’t absolutely claim that the slick tread was the reason for these crashes, but it doesn’t seem to have helped either, and so I lost faith in those tires and am going to change them at the earliest opportunity (guess what I’ll be buying instead…).

    September 26, 2014 at 6:57 am
    • Jan Heine, Editor, Bicycle Quarterly

      The hand-made tires of the 1930s and 1940s had slick treads, since the small makers couldn’t afford molds. I assume they just glued strips of rubber on their tires. These tires had a reputation for being slippery in the wet. Of course, it could have been due to the rubber compound, too…
      Generally, slick tires have a poor reputation for wet-weather grip. That matches my experience. The worst were the last-generation Avocet tires, which I could spin taking off from a traffic light on a wet, but otherwise clean road…

      September 26, 2014 at 7:20 am
  • Oscar Dube

    Dear Jan,
    to quote:

    This is what I used to believe, too, before I had much experience riding with many different tires.

    Sorry, I could say the exact opposite based on experience too (and provide plenty of documentation from my riding log to bore you to death).

    Drag a piece of coarsesandpaper across the road, then a piece of cardboard. […]

    That’s just apples with oranges. Sandpaper is completely different to cardboard, and compared to rubber it is super hard. It is made to abrade material that is softer, and that includes concrete, asphalt, steel and stone, depending on the type. Just try to compare different grades of coarse sandpaper for that matter, or of types of cardboard. Doesn’t simulate sandpaper the situation with studded tires on soft surfaces better? Does cardboard with fins grip the asphalt better?
    For now, tires are made of rubber that is softer than the pavement, and everything else follows. The soft Rubber can’t grip anything. The asphalt “bites” the tread, and studded MTB tires “bite” sand and other stuff.

    Feel and experience are much better than theoretical reasoning.

    And data is better than feel, and you have no data. You also have no good theoretical reasoning at this point, sorry to say that. Since you have no data, your theory must hold up. In order to do that, it should, amongst others, explain what the optimum tread properties should be: size and depth of the pattern etc. But that’s impossible, because there are indefinite patterns of pavement out there to match. (It’s different off-road, as explained…) So you go on:

    A sandpaper-like pattern wouldn’t work well in rubber: The little knobs would just flex. The chevrons of the “file tread” provide a more rigid pattern.

    First, it’s all tiny shapes of rubber, so rigidity is a wash. Second: you made a point before about interlocking cogs. How can you explain which road irregularities are “gripped” by the chevron and which not? Sometimes it would fit, sometimes not, only IF it was rigid enough. But anyway, it’s not, so the flimsy chevrons squirm wildely, while keeping oher parts of the rubber surface from contacting the grain of the pavement.
    To make it short: What precisely makes your pattern better suited than any other of the bazillion patterns out there? Can you explain it precisely?

    Be careful! I wouldn’t crash on purpose – unless you do it as a very controlled experiment, it doesn’t advance science, and you might get hurt.

    Thanks for caring, you’re welcome. Yes these are experiments, they sometimes did hurt, but it did advance my understanding of which tires to buy and which not greatly. I could supply a list of pure slick tires I tried and of tires with treads like you propose, and which slipped and which not. To sum up, it came out that performance was mostly defined by the compound. By purposefully over-braking in the wet, the foul ones reveal themselves. Some brands hold their promises, others not, and size matters, tread-patterns not. In fact, the worst traction I ever experienced came from Panaracer Paselas that slipped away on dry pavement!

    September 26, 2014 at 10:43 am
    • Jan Heine, Editor, Bicycle Quarterly

      The same type of reasoning was used (by the same people) to defend the idea that higher pressures make tires faster, that frame stiffness does not matter, that fork blades don’t and cannot flex, that low-trail geometries must be unstable…
      In the end, it has been the on-the-road experience that really has moved us forward. The “fine file” tread pattern has evolved over many decades, like so many things on bicycles. It appears to work well, certainly better than slicks. As a rider, that is what I care about.

      September 28, 2014 at 4:40 am
      • Sree

        After reading up on old Brandt posts, there may be alternative explanation that may hold, and that may be easily tested.
        Brandt’s main argument was that rubber tread patterns were simply not sharp enough to cut through the boundary layer of water between the road and the tire — only micro-grit from the road could do that. From these statements, a logical next step could be that tread patterns increase micro-grit retention on the tire (perhaps by providing secure retention for the micro-grit) and the now micro-grit encrusted tire can cut more easily through the boundary layer providing better traction.
        So, the experimental question is: Does a dirty micro-grit encrusted tire provide better grip on a wet steel roller than an equivalent clean tire with or without tread patterns? Of course, the effects may be marginal on steel rollers. The steel roller also does not replenish the micro-grit, so this experimental setup may need to be considerably improved to obtain meaningful results. Maybe somebody has already studied this setup?

        September 28, 2014 at 11:03 am
        • Jan Heine, Editor, Bicycle Quarterly

          I think Jobst’s mistake was that he was thinking of a smooth surface with a uniform layer of water on it – like a steel plate. On a steel plate, I doubt any tread makes a difference.
          However, the road surface has many irregularities, and there is not a uniform layer of water covering it all. So the interlocking is a totally different mechanism from the one Jobst assessed.

          September 28, 2014 at 12:05 pm
  • Matt Sallman

    Years ago I rode Michelin SuperCompHD tires and loved them. They were a very round tire cross section and I felt confident cornering with them. More recently friends recommended Continental Grand Prix 4000 tires and I never felt comfortable with their oval shape. I switched to Pro3s and felt better going back to the round tire.
    Thankfully when I was finally ready to try 650b tires the new Compass tires had just been introduced. I bought a set of Babyshoe Pass Extra Lights. The 42mm tires on my new Grand Bois rims (23mm) are a very fat, round tire. I have never ridden a tire that made me more confident of the cornering grip as these. And the extra comfort is just an added plus. I rode a 200K brevet in May that included some very rough pavement and I was able to continue much faster than my riding partner on his 28mm tires.
    While not a controlled test, I have done rides on my steel 650b bike and compared it to my older Aluminum/Carbon bike with 700cx25 tires and found no speed advantage to the “racing” bike even though it was a full 10 pounds lighter than the steel bike. It would be interesting to see what that bike would do on supple Compass tires, but the 650b bike is so pleasant that I don’t know if I would want to bother.

    September 26, 2014 at 5:45 pm
  • don compton

    From a strictly non-scientific point of view, bigger tires made with light,flexible casings are much more pleasant to ride and, for me offer no performance disadvantage. You guys can argue over different theories all you want, but in my many miles, but not scientific experience, skinny, high pressure tires are not fun on bumpy, pot hole filled roads. And we have many in California. Even my wheels keep their true longer. Once riders try the wider tires, at lower pressures, they have big smiles on their face. NO BRAINER

    September 26, 2014 at 8:15 pm
    • Jan Heine, Editor, Bicycle Quarterly

      That is sort of what we figured when we designed these tires. In the worst-case scenario, the tread would just be ornamental. (Our tire tests had shown that a fine tread doesn’t make tires slower.) In the best-case, the tread would work as we had envisioned, and improve cornering traction. Either one would be an acceptable outcome. Our on-the-road experience seems to indicate that the tread works as intended, but compared to the benefits of wide, supple tires, it’s minor.

      September 26, 2014 at 8:53 pm
  • Wil

    The speed in mph at which a tire will hydroplane is roughly 9 times the square root of the tire pressure in psi. So a tire at 50 psi will hydroplane at about 63 mph. This is why you don’t see bicycle tires hydroplaning. Bicycles rarely reach the speeds necessary for the phenomena to be observed. It has nothing to do with the size or shape of the contact patch because the weight of the bicycle is distributed evenly over every square inch of contact patch.

    September 27, 2014 at 6:17 am
    • Jan Heine, Editor, Bicycle Quarterly

      If the size and shape of the contact patch doesn’t matter, then why do car tires use channels in the tread to prevent hydroplaning? All that does is reduce the size of each individual contact patch, breaking one large tire up into many small ones, with a little space in between.
      In the end, it doesn’t matter for bicycles. Pressure is directly linked to contact patch size. We all agree that bicycles don’t hydroplane, hence the big sipes that many tire companies put on their tires don’t make sense.

      September 27, 2014 at 6:28 am
      • Andy

        This might be a different type of hydroplaning, but I used to seek out tires with deep grooves for a commuter bike that I rode in snow. My theory was that a 28mm front tire with grooves would help cut through slush on the road, while the 35mm cross tire in the back would provide more traction to the driven wheel. It made sense in my mind at least, but I wouldn’t call it scientific. I never crashed on snow/ice/slush though.

        September 27, 2014 at 1:33 pm
  • robertkerner

    First I’d like to thank you for offering fine alternatives to the other brands of tires out there. I have a year on my Grand Bois and they ride nicely and are flat-resistant even in the NYC area where the roads are crappy. I don’t particularly care about the math behind whether they should ride nicely or not. They do, and that’s all that matters to me coming from years of riding skinny overinflated tires.
    What in your tire line up do you suggest for wet weather, autumn and early winter riding?
    I’ve been running Conti’s Top Contact Winter, but they ride like bricks. What tread patter do you like in the wet Northwest?

    September 27, 2014 at 9:36 am
    • Jan Heine, Editor, Bicycle Quarterly

      I ride the same tires year-round. The tread pattern of the Compass tires works really well in the wet, and the black tread grips best in wet conditions, too.

      September 27, 2014 at 9:47 am
  • Michael

    How does the 650b Cypres tread file pattern compare to the 650b Compass tread file pattern? They look similar.
    Would a future 32mm 650b Compass tire perform alot differently than the Cyprus?

    September 28, 2014 at 11:39 pm
    • Jan Heine, Editor, Bicycle Quarterly

      The differences are very slight. The Cyprès tread is a little thicker on the shoulders, and it doesn’t have the smooth part at the edge. Both tread patterns are excellent…

      September 29, 2014 at 5:22 am
  • Charles Nighbor

    aren’t these comments about tread design a bit silly. with tread pattern so shallow that in a few 100 miles the main treat pattern on the top of the wheel is worn smooth and your riding on a slick tire from that point out except when you make a turn
    Charles Nighbor Architect

    September 29, 2014 at 9:28 am
  • Waldo

    While this is not a tire tread comment, it is relevant to tire adhesion issue: Jan, I am sure I speak for many 700c wheel users when I ask that Compass Cycles bring to the market a 700c tire wider than 38mm. A 42 would be wonderful. Thanks very much.

    September 29, 2014 at 11:06 am

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