Why slick tires don't stick well

Why slick tires don't stick well

During the R&D of the Compass tires, I was surprised how much difference tire treads can make. I rode three sets of tires with the same casing, same tread rubber and same width, but different tread patterns:

  • standard Grand Bois Hetres with large longitudinal ribs throughout the tire tread
  • “shaved” Hetres where all tread had been removed to make “slicks”
  • prototype Compass Babyshoe Pass tires with our optimized tread pattern

I crashed on the shaved Grand Bois Hetres when the roads got wet. I made the mistake of leaning over as far as I would have on the standard tires, and found that they offered much less traction in the wet.
During my first ride on the Compass Babyshoe Pass tires with their small angled ribs, I almost hit the inside curb. The extra grip of the new tread pattern made the tires corner on a much tighter radius, for the same rider input.
It became clear that slick tires provide relatively poor grip, especially on slippery road surfaces. And large ribs squirm and thus make the bike “run wide”. Why?
How do slick tires work on racing cars and motorbikes? Slick tires for racing cars are so soft that they form a perfect imprint of the road. They interlock with the irregularities of the road surface. This means that they don’t rely only on the coefficient of friction for grip, but also form a mechanical lock on the road surface.
The downside of the soft tires is that they wear out in just a few hundred kilometers. Often, race cars need to change tires several times during a race. And once the road gets wet, slick tires go from phenomenal to almost zero grip. Water forms a very effective lubrication layer between tire and road (“hydroplaning”).
All this isn’t optimal, but car designers have no choice: Their tires use the same surface for cornering and acceleration. Any tread pattern fine enough to interlock with the road would be ripped off the first time the driver steps on the gas. The same applies to racing motorcycles, which put down a lot of power while still leaning over as they exit corners.
In fact, the more powerful racing motorbikes can be “drifted” to safely approach (and exceed) the cornering limits. This would shred any fine tread patterns.
Bicycles are very different. They coast around tight corners. As a result, they use different parts of the tire for cornering and for accelerating. Here is how that translates into an optimized tire tread for road bikes:
When the bike is going in a straight line, the tread doesn’t matter much. Cyclists don’t have enough power to spin their wheels, and bike tires are too narrow to hydroplane. There is no need to evacuate water from the road/tire interface, and deep groves like those of a car tire serve no purpose.
The center portion of a tire can be slick, but we make ours with fine longitudinal ribs as a wear indicator. Once that tread is worn smooth, you have used up about 30-40% of the tire’s lifespan.
Dots or ribs that are angled or perpendicular to the tire’s rotation might increase the rolling resistance: They have to flex as the tire rotates. Perhaps it doesn’t matter much: The center portion of the tire will eventually wear smooth and become “slick”.
This is where it gets interesting. The tread on the shoulders provides traction when cornering, so it’s of great importance. You spend relatively little time leaning into a turn, so this part of the tire does not wear. The shoulder tread can be designed for optimum traction without compromise. How do we get the same “interlock” as the race car slick tires?
The best solution is to provide little ridges that “catch” on the road surface irregularities and thus interlock with the road surface. One advantage compared to the slick race car tires is that the ridges cut through the water when the road is wet, thus providing the interlock even in the rain. On wet roads, the coefficient of friction between road and tire is reduced by more than 50%, so the interlock between tire tread and road surface becomes much more important.
This idea of interlock between tire tread and road irregularities is nothing new. Michelin’s engineers pointed this out in a paper in the 1980s Bicycle Science Newsletter, and even then, it wasn’t presented as something new or revolutionary.
Since the pavement aggregate is random, you want to provide as many interlocking surfaces, oriented in as many directions, as possible. By making the tread as fine as possible, you have a good chance that a rib lines up with the edge of a piece of aggregate in the pavement. That is why small ribs work best. The ribs need to be strong enough that they don’t squirm during cornering (like knobby tires do). Otherwise, you’d reduce your cornering grip again, and also increase the tire’s rolling resistance. Fortunately, the ribs don’t have to be tall, which reduces how much they can flex.
That is how you arrive at a criss-crossing pattern of fine ribs to provide a maximum of interlocking surfaces. This type of tread pattern was standard on high-performance bicycle tires for so many years, and it appears that there was good reason for this. In the old days, rubber compounds were much less evolved and provided less friction especially in wet conditions. Without the interlocking ribs, the tires would have been very dangerous in the wet. Modern rubber compounds have improved the coefficient of friction, but interlocking still is important for grip, especially in the wet.
The outermost part of the tire tread never touches the ground. You only need it to protect the tire casing from cuts. This tread can be thin and doesn’t need any pattern.
That is the logic behind the Compass tire tread. It’s not complicated, but it seems to be the only way to optimize a bike’s tire tread. We aren’t the only ones to use this type of thread. It used to be common on most high-end performance tires, and today, a number of companies still use it.
Let’s look at the alternatives:

  • Slick and coarse tire treads give up many opportunities for interlocking, and thus will offer relatively poor grip, especially in the wet.
  • “Negative” treads, that just cut grooves into the tire, apparently are inspired by car tires, where they help prevent hydroplaning. But even very wide bicycle tires are too narrow for hydroplaning (and our speeds are too low, too). Perhaps a fatbike with slick tires at 50 mph could hydroplane…
  • Knobs will squirm in corners and thus make cornering unpredictable and dangerous. (Knobs are useful for traction in mud and snow, though.)

Back to the title: Slick tires are based on a simplified, incomplete understanding of tire grip. They offer less traction in dry and, especially, wet conditions.
Better tire treads exist. It’s important, because the tread pattern makes a very significant difference in how well a tire grips and performs. Being able to lean into a corner with confidence makes cycling both safer and more fun.
Click here for more information about Compass tires.

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Comments (53)

  • velofinds

    Reblogged this on Velo Finds.

    January 5, 2016 at 6:43 am
  • James

    I find your explanation of file tread quite convincing but I’m still a bit confused about your implication that very soft rubber compounds can’t be used in bicycle tyres.
    Wouldn’t a soft-compound tyre last reasonably well on a bicycle thanks to the cyclist’s relatively low power/acceleration? And how do regular, high quality road motorcycle tyres achieve great grip in the wet and dry while lasting at least 5000 miles (in my experience)?
    I believe most or all good motorcycle tyres use different rubber compounds for the center and the sides of the tread to give both good wear and good cornering grip. Would it be too expensive to make bicycle tyres in this way? Is the file tread simply a more economical way of reaching the same goal?

    January 5, 2016 at 6:53 am
    • Jan Heine, Editor, Bicycle Quarterly

      Using a soft compound for the entire tire would reduce its lifespan to unacceptable levels. Some may remember the Michelin Hi-Lites of the early 1990s – great grip, but it was rare to get more than 1000 miles out of them.
      We’ve talked to Panaracer about using different tread materials for the center and sides. The problem is the transition, and the uneven wear you’d get there.

      January 5, 2016 at 7:19 am
      • Bill Gobie

        Does tread thickness affect the feasibility of using multiple rubber compounds? Schwalbe makes tires with two or even three compounds. I’ve never noticed uneven wear, although being narrow high pressure tires I rarely wear the tread off before a large glass cut kills the tires. Schwalbes generally have thicker treads than Compass tires.

        January 5, 2016 at 8:25 am
    • Marco

      Hi James,
      I’m no expert, but I guess that motorcycle tires are a lot thicker than bicycle tires, the latter having to be very thin to minimize at all costs rolling resistance. Maybe for this reason motorcycle tires can use a soft compound and yet be durable enough?
      Also, motorcycle tires are a lot wider than bicycle tires, and this should give them better traction and grip.

      January 5, 2016 at 4:05 pm
    • Marco

      Here’s an example of the cross section of a motorcycle tire:

      January 5, 2016 at 4:06 pm
  • lobodopampa

    I’m running 700-28 Compass tires on my go-fast bike, which is a high racer recumbent, and love them.
    Now I’d like some supple and wider tires for my urban bike, which is also a recumbent (rear suspended Euro style SWB).
    Your 26″x1.75″ tires would be perfect, but I’m a little concerned about the thread. It looks nothing like the tires you described on this post. What’s the reasoning behind it? They look like they would pick lots of little tiny rocks. The side walls look somewhat awkward to my eyes, also.

    January 5, 2016 at 7:06 am
    • Jan Heine, Editor, Bicycle Quarterly

      The narrower 26″ Compass tires use existing Panaracer molds. We could not choose the tread pattern, so it’s not as optimized as we’d like. These tires still use the Compass casing, so they offer a better ride and performance, but their cornering isn’t as good as that of the tires we designed from a clean sheet of paper.

      January 5, 2016 at 4:17 pm
  • marmotte27

    Very nice explication, even better than the one published in BQ a while a go.
    Unfortunately I cannot fully fathom and benefit from the cornering abilities of my Loup Loup Pass tires. I crashed twice while cornering on a slick tire, the second crash sending me to hospital, and I’ve lost much of my confidence when cornering. I just don’t dare take those tires to the edge.

    January 5, 2016 at 7:34 am
  • Tran

    Why then were the Elk Pass designed without threads ? My Elk Pass shod rear wheel recently slipped out beneath me in a roundabout.

    January 5, 2016 at 7:36 am
    • Jan Heine, Editor, Bicycle Quarterly

      The Elk Pass 26″ x 1.25″ also uses an existing Panaracer mold. There isn’t enough demand in that size to allow for making a new tire mold, which is very expensive. The Elk Pass uses our Compass casing, both in standard and extralight versions, so you still get a very supple tire with excellent comfort and performance.

      January 5, 2016 at 4:19 pm
      • Bill Gobie

        When I heard about the Elk Pass I wondered if Compass had revived Panaracer’s EVO tires. Comparing an Elk Pass to my last remaining EVO II, it looks like you are using the EVO molds and an even lighter casing and thinner tread. The EVO molds explain why the tires are undersized (~28 mm vs 32 mm claimed) while your other tires seem to be accurately sized. EVOs were excellent, fast tires and Elk Passes seem even better.
        Any chance of making a 26×1.375 that would need less pressure than the Elk Pass? My bike won’t fit a 1.5 on the rear wheel.

        January 5, 2016 at 5:12 pm
  • Steve Palincsar

    It’s unclear whether anyone besides you as ever seriously attempted to understand bike tire tread design. So much does seem to have been based purely on appearance and copying others.

    January 5, 2016 at 7:37 am
    • Jan Heine, Editor, Bicycle Quarterly

      I don’t think all those “file” or “chevron” tire treads of the old days came about by accident. With older rubber compounds that offer less grip, mechanical interlock was more important, and the better tires were optimized for it.

      So much does seem to have been based purely on appearance and copying others.

      My sources at Panaracer confirmed that in recent years, “design” has been driving the tread patterns used by most of the industry.

      January 5, 2016 at 7:48 am
  • Jason

    I have been very interested in tire siping and how it could be applied to bicycle tires. Many winter car tires (e.g. Bridgestone Blizzak) feature extensive siping for traction on snow and ice. Les Schwab also offers post processing tire siping and touts many additional benefits.
    Have you ever considered manually adding siping to investigate possible benefits with bicycle tires?

    January 5, 2016 at 8:53 am
    • Jan Heine, Editor, Bicycle Quarterly

      As far as I understand it, siping works by providing cavities that suck water from the tire/road interface. The ribs of the Compass tire tread may work the same way, but I think the “interlock” is more important. Car tires cannot use ribs as fine as those of bicycle tires, as the ribs would wear off quickly. Also, the tread of bicycle tires is much too thin to add sipes.

      January 5, 2016 at 5:20 pm
  • Ryan

    The world is wrong but you are right.
    Whenever I hear this sort of thinking I am very skeptical. Like denying climate change, you have done some reasonable level of research but nowhere near the amount needed to make this claim:
    “it’s really the only way to optimize a bike’s tire tread”
    Is the point of the post informative or commercial in nature?
    And “my sources at panaracer” is not good enough.
    Assume much, prove little is no way to educate people but it does resemble the kind of thinking found in cult literature or religion.

    January 5, 2016 at 9:07 am
    • Jan Heine, Editor, Bicycle Quarterly

      Most bicycle design has been done by trial and error. It’s hard to prove that double-butted tubing provides better performance, yet when it became widespread in the early 1930s, racing speeds went up significantly. Of course, other factors also could be at play. In the end, the best we can do is ride a few bikes and decide which we like best. At Bicycle Quarterly, we design experiments that limit the variables. The same was done with the testing of three tires of identical width and construction, but with different tread patterns.
      If we just wanted to promote our tires, we’d use a tread design that is unique to our tires (and ideally patented), and then tout its supposed superiority. We used a tread pattern that is available from a variety of companies, because we feel it works best. We invite you to try different tires and form your own conclusions.

      January 5, 2016 at 5:25 pm
    • marmotte27

      “Assume much, prove little”
      That is the approach of most of the bicycle industry. Pages of publicity are dedicated to it, and even whole magazines, indeed most bicycle magazines function this way, doing “testing” that does little but confirm preconcieved notions about bikes, components and their supposed benefits. Take frame stiffness for example, for nearly two decades now, frame stiffness has been touted as the be all and end all of bike design, magazines tested stiffness and claimed that the stiffer bikes are faster, something that nobody could ever prove, and which, as Jan and his friends have shown is probably completely wrong.
      Don’t you see that in this world a magazine like BQ and people like Jan, who do not function on assumptions, who are questioning all those beliefs that have no real basis in fact, who do not “innovate” first of all for commercial reasons, who have a real background in science, are the exact opposite of what you accuse them of being?

      January 6, 2016 at 2:22 am
  • nickskaggs

    The Soma Green Label GR tires are slick in the center and have very fine longitudinal ribs on their edges, and I’ve found them to be very slick- I’ve slid out once on them in a corner in the rain and I’ve had a few near slips on them on corners that felt fine on my old Challenge tires.
    Maybe some new Compass tires are in my future- once I wear these out. In the interim, winter might be hazardous… 😉

    January 5, 2016 at 10:13 am
  • Wilfried531

    Are you saying that Hetre tires aren’t safe in wet conditions ?
    I feel concerned, I’ve just bought 4 EL Hêtre tires for my new bike wich should be finish in a few weeks…
    I’m used to GB Cyprès with tread pattern, I hope I won’t be desapointed…
    And you know , you are Gospel truth for me 😉
    With years, you’ve just changed my vision of what a bike should be!

    January 5, 2016 at 10:18 am
    • Jan Heine, Editor, Bicycle Quarterly

      The Hetres are safe, and with the extra rubber on the road, they’ll corner as well as the narrower Cyprès. However, they could corner even better, if the tread was more optimized… It was the shaved versions (without any tread) that slid in the wet.

      January 5, 2016 at 4:23 pm
  • Luis Bernhardt

    Refreshing article. I remember that Jobst Brandt was very adamant that cyclists needed only a slick tire, and the Avocet tire line reflected his influence. I can’t imagine that he rode only on dry pavement. Here in the Pacific Northwest, tires need to be able to handle anything. I’ve been using Vredestein TriComps, which reputedly use different rubber densities for middle and shoulders. But I don’t think the sidewalls are as supple as you would probably like, as they appear to be thicker so they last in wet weather (unlike Contis, for example, which have thin sidewalls, but they tend to rot/become weakened when wet). How durable are the Compass thin sidewalls when used daily in wet conditions?

    January 5, 2016 at 12:32 pm
    • Jan Heine, Editor, Bicycle Quarterly

      I cannot comment on Jobst’s riding style, but the last-generation Avocet tires were very slippery in the wet. Of course, that was probably after Jobst had anything to do with them.
      Compass tires have lasted well on my Urban Bike, which gets ridden year-round in wet Seattle urban traffic.

      January 5, 2016 at 4:25 pm
  • Conrad

    It is nice that someone is thinking critically about treads and not just following trends or confusing ad copy with thoughtful design. That being said, I think it is really difficult to critically evaluate the traction of a front tire on pavement. It is really, really hard to drift the front tire on pavement: once the front tire loses traction, you are going down. Most times that I have washed out the front wheel, ice/sand/gravel/moss have been the main culprit. Testing the upper limits of traction on wet but otherwise clean pavement is not a job I would want to sign up for.
    Knobs are another story. People need to realize that knobs are for mud only. They don’t do you any good on ice, sand, gravel, or any hard surface. Yet there is a preponderance of knobby tires, the vast majority of which don’t even have a proper profile for mud (tall, well spaced knobs!). Also, riding trails on file treads is no big deal. Whereas riding pavement on knobby tires is very literally a drag.

    January 5, 2016 at 12:38 pm
  • Jay Guerin

    During the 1,000 miles, or so, I’ve put on my Riv Bleriot with Grand Bois 650Bx42 Hetres I’ve experienced 3 very scary slide outs of the front wheel. In each case I was in a less than 10 mph turn when the wheel slipped to the side about a foot then grabbed traction. In each case I was able to correct their situation without going down. This has never happened with any other tires on this or any other bike. The last time was while making a left turn in an intersection about a month ago. Your thoughts?

    January 5, 2016 at 12:44 pm
    • Jan Heine, Editor, Bicycle Quarterly

      I am surprised to hear that. In my experience, the Hetres do run a bit wider on the limit (high-speed cornering), but don’t suddenly loose traction. Could it be that you simply are going faster than you are on your other bikes, since the wide tires give you so much more confidence?
      Also, which color Hetres do you use? The white tread offers significantly less traction in the wet than the black, and the red is somewhere in between. That is why we don’t offer different tread colors on our Compass tires.

      January 5, 2016 at 5:27 pm
      • Jay Guerin

        I have the red ones. Your comment on the properties of various colored tires is interesting. Never heard that before. All my others are black.

        January 7, 2016 at 7:57 am
  • Michael

    My rear Loup tire center tread is worn down now to slick. Is it safe to keep riding it until I start to barely see the tan beneath the tread? I inspect them often. I have heard of folks like to ride until the casing starts to peek through the tread.

    January 5, 2016 at 11:41 pm
    • Jan Heine, Editor, Bicycle Quarterly

      Don’t ride the tire until the casing peeks through. You risk a blowout, and a hospital visit costs much more than a new tire! When in doubt, take the tire off and feel it between your hands as you flex it. You’ll notice how much tread is left.
      When you do replace the tire, cut the old one in half. Check how much tread was left. That gives you an indication how close you’ve been cutting it…

      January 5, 2016 at 11:52 pm
  • Alan

    Would you recommend a Compass Tire for touring purposes? I’m sure they ride great, but I’m wondering about puncture resistance.

    January 5, 2016 at 11:57 pm
    • Jan Heine, Editor, Bicycle Quarterly

      It depends where you tour. On empty backroads, you are unlikely to get flats anyhow, since you ride on the road surface that gets swept clean by the (occasional) car that passes.
      If you ride on the shoulders of busy highways, where debris (and especially the steel wires from exploded truck tires) accumulates, then you are more likely to have flats.
      Beyond that, the wider the tire and the lower the pressure you run, the less likely you are going to have flats, because the tire simply rolls over debris that gets hammered into a narrower, harder tire.
      So to summarize, I do tour on Compass tires all the time, and the last flat was many thousands of miles ago, when my tire picked up a steel wire on the shoulder of a busy highway last spring.

      January 6, 2016 at 12:09 am
    • Tony Hunt

      I did a tour last summer in Minnesota with my Compass Tires and didn’t flat once!

      January 6, 2016 at 2:36 pm
      • Jason Marshall (@jmarshall312)

        Yeah, I’ve ridden my LLP ELs around three of the Great Lakes, Paris Brest Paris (plus the SR brevet series to qualify) and numerous – numerous additional day rides and I have had exactly one flat. The funny thing is that the flat came on the very first day I mounted them 🙂 It helps to rotate the back to the front to keep wear even.

        January 7, 2016 at 6:24 am
  • Michael

    What’s the difference between “rolling resistance” and the friction you mention in “coefficient of friction”?

    January 6, 2016 at 7:58 am
    • Jan Heine, Editor, Bicycle Quarterly

      I am referring to the coefficient of friction as the tire corners. You want as much as possible, so you don’t slide. It’s basically the friction that would occur if you drag the tire (wheel not turning) across the road.
      Rolling resistance is the resistance that occurs as the tire rolls down the road. It is caused by numerous factors, mostly the deformation of the tire as it turns, as well as the suspension losses due to the vibrations of the bike.

      January 6, 2016 at 5:03 pm
  • Steve Green

    Some tyres have direction arrows on the sidewalls. On customers’ bikes (i’m a mechanic) I always fit them with the arrows pointing in the specified direction. However, I don’t believe that this is relevant (it might be so with radial tyres, as on cars).
    Comments, please!

    January 6, 2016 at 8:39 am
    • Jan Heine, Editor, Bicycle Quarterly

      All the experts I have talked to believe that “directional” treads on road tires are about marketing, not function.

      January 6, 2016 at 5:03 pm
  • ryanfrancesconi

    Hi Jan, Thanks for these tires. I’ve been riding the Babyshoe pass ones over some crazy stuff the last months and am very happy with them. Best all round tire I’ve tried yet. And now a tubeless question – which I know you’ve had to answer so many times about these tires, but I can’t find a definitive answer to something. I have been running them with tubes (standard casing, not extralight) with the idea to convert them when I had time. I had time yesterday and found that the casing is too porous for tubeless. Sealant oozed out of the sidewalls and bubbled up. Kind of a mess. Here’s my question – I know these aren’t rated as tubeless compatible, so I’m not shocked – however will the all black casing be more solid? Are those a single vulcanized tire? I am using the tan sidewalls. It seems that there is a big need for a tubeless babyshoe!
    Thanks again for these!
    Ryan Francesconi
    Portland, OR

    January 6, 2016 at 8:52 am
    • Jan Heine, Editor, Bicycle Quarterly

      To make the sidewalls less porous, we’d have to add more rubber, which would make the tires less supple. However, many customers and also BQ contributor Hahn Rossman have set up Babyshoe Pass tires tubeless without problems. They use Stan’s sealant, and they swish it around inside the tire, then lay the wheel on its side and turn it over from time to time. Within a day or so, the tire seals.

      January 6, 2016 at 5:09 pm
      • Harald

        Possibly stupid question: Wouldn’t the sealant filling the pores in the sidewall then not also make them less supple?

        January 8, 2016 at 5:12 am
        • Jan Heine, Editor, Bicycle Quarterly

          Good question. I think there is so little sealant that it’s not significant, especially since you eliminate the inner tube, which also stiffens the tire. The general consensus is that a tubeless tire with sealant is much more supple than a tire+inner tube.

          January 8, 2016 at 4:28 pm
  • Alexander Fine

    Love the article!
    I have a very odd “negative” tread on the shoulders of my Continental Gatorskin tires. It also has a “negative” wear indicator. They feel fine but I had a set of Vittoria techno twin tread tires years ago that had a file tread and loved their grip and road feel. Sadly they flatted very easily and I gave up on them.

    January 7, 2016 at 10:58 am
  • thebvo

    We are still waiting for the next set of roll-down tests. The Compass tires have never been tested this way in a BQ article. How is that possible? Whenever I grab a BQ issue out of the box, I always gravitate towards the old ones. There used to be so many articles about tests, and technical stuff (frame tubing/ stiffness/ geometries, aerodynamics, braking, choosing gears, front-end geometry, wheel flop, etc etc etc). Those have greatly increased my knowledge on many subjects and I’m always excited for a refresher. It seems that the tire tests and other tech stuff have lost some of the priority alongside the ride reports in BQ. We bike-nerds love those graphs n maths n tests n charts too!

    January 7, 2016 at 12:41 pm
    • Jan Heine, Editor, Bicycle Quarterly

      We will do more tire tests, but Bicycle Quarterly is independent of Compass, and so we won’t just go out and show that the new Compass Extralights are faster than the Grand Bois we’ve tested in the past… That would be mere advertising.
      The goal for Bicycle Quarterly always has been to do basic research into what makes a tire perform, not just product testing that becomes outdated as soon as the next model year comes around. That is why our tire tests had such a lasting influence, whereas other tests simply declared a “winner” among current tires.
      We tested until we had answered all questions that we could answer. At that point, we stopped testing. We could try and test grip on different surfaces, but it’s very difficult, and the results would apply to that surface only. One thing we do want to test are tubeless tires. We also want to determine how wide a tire can get before its performance drops off. The new Compass tires go all the way to 52 mm, so we now have an opportunity to do this.
      As you can see, a new round of tire testing is firmly in the plans, we just need to schedule it and wait for perfect conditions to minimize “noise” in our data. (No wind, constant temperatures.) There are other technical articles in preparation – you’ll find more of them in future issues.

      January 8, 2016 at 1:41 am
  • Ed B

    Theorists vs Empiricists is what it comes down to. I remember listening to my Noble Prize winning Physics Professor lay down the laws about friction and alls I wanted to do was take him to the strip in my 1970 Z28 and swap tires back and forth and let drive and explain the length of burnouts and difference in ETs. Anyways, I KNOW my Compass tires corner better than all the others in my stable. I don’t need no theory. If tread design does not matter why can I mindlessly float along while negotiating a favorite downhill, bumpy sweeper on my daily training while on my Compass 28 or 32 mm EL tires whereas the same corner gets my full attention riding Vittoria Corsa CX (28mm), Continentlnal 4000 Sii (31.4 mm), VeloFlex Masters (24.5mm) , Schwalbe One’s (27 mm), or maybe to a lessor extent Challenge Parigi Roubaix tires (32mm)? Some of these tires are labeled 25 mm and some are 28 mm but many of them are much puffier (figures above in parenthesis are the measured widths) than the sidewall label indicates unlike the Compass tires which measure right on the money (a 28 is a 28 and a 32 is a 32mm, on my rims anyway). I ride all of these tires and have done so on 600K Brevets but if I want comfort, acceptable speed, and reasonable tire life, only the Compass fits that requirement. The Challenge tires are also nice but they get me well less than 1000 miles…..much less than what I get from a Compass.
    “Theorists and Empiricists”……..It is interesting that Schwwalbe put side tread on its new Pro One Tubeless merely to satisfy the complaints of professional riders, according to Peloton Magazine….as if the Pros are rubes. I have a set of these in 28 mm on the way, I guess I have a tire fetish.
    “Schwalbe got tired of explaining to pros and amateurs alike that a slick tire created as much, if not more, traction in all situations so they added some purely cosmetic tread.”

    January 8, 2016 at 5:00 am
    • Jan Heine, Editor, Bicycle Quarterly

      We are firmly in the camp of the empiricists, since that approach has always yielded the best bikes. Even today, the best racing tubulars are made by FMB, a small outfit in Brittany, un-matched by all the research the big makers have put into it.

      January 8, 2016 at 4:26 pm
      • Steve Palincsar

        And correct me if I’m wrong, but aren’t those FMB tubulars the most traditional, old-timey tubulars currently available?

        January 9, 2016 at 6:05 am
  • SmoothestRollingBike

    Jan, if you really want to determine how wide a tire can get before its performance drops off,
    PLEASE, PLEASE include in your tests the newest 2016 Schwalbe tire.
    Schwalbe Big One LiteSkin 60-622 (29 x 2.35)
    Weight: 440 g
    OneStar Compound (the best Schwalbe’s compound)
    EPI: 127
    The old one was like this:
    Schwalbe Super Moto 60-622 (29 x 2.35)
    Weight: 680 g
    PaceStar Compound
    EPI: 67
    Schwalbe Big One is almost as light as Compass 26 x 2.3 Rat Trap Pass Extralight model (418 g).
    I think Schwalbe Big One would be the best competitor in your tests with Compass tires and could answer the question if you could make EVEN WIDER COMPASS TIRES than Rat Trap Pass.
    I’m sure you should.

    January 8, 2016 at 12:58 pm
  • Richard

    The empiricist vs theorist discussion hints at an issue that becomes increasingly important near the limit of adhesion. That issue is the relationship between g force and slip angle. Tires that produce the highest lateral force do so at a small slip angle. They also give scant warning that you’re approaching the limit. Push a little too hard and they lose traction abruptly. If you regain traction before you crash, the consequence can be even worse – a “high side” crash. IIRC, the accepted terminology for tire behavior at the limit of traction is breakaway and recovery. The ideal tire would combine maximum lateral force and gradual breakaway and recovery. The problem is, you can’t have both; one comes at the expense of the other. In reality, the most desirable tire is the one that best balances adhesion and predictable behavior. Thank you, Jan and associates, for your ongoing contributions to the development of high performance user-friendly tires.

    January 8, 2016 at 11:39 pm
    • Jan Heine, Editor, Bicycle Quarterly

      With bike tires, perhaps the most important thing is being able to feel how much traction is available. If the breakaway is sudden, you need to stay far from the limit to be safe.
      On gravel or mud, the limit is so gradual that you can safely approach and even exceed it – great for practice.

      January 9, 2016 at 12:54 am
      • mike

        I second the last point.
        I have a 1990 MTB. Even with some 2.2″ MTB tires the bike feels a bit lightweight in front, but I never had a bad feeling in fast corners with tires with moderate nobbies.
        I installed the Rat Traps on it. Comfort and speed is excellent, but the new tires added a new feeling, similar to what you described as a result of a fine pattern – “The extra grip of the new tread pattern made the tires corner on a much tighter radius, for the same rider input.”
        Even after ~200km I don’t feel good with that behavior and therefore I cannot ride the bike with that tires to its limits at fast corners. It’s probably special to my bikes geometry, it’s mixing up effects of thread, wheel flop, pneumatic trail and some more. But it brings me to the question if such an extra grip is always preferred, or if there is something like a best matching tire/thread for a given geometry? Like you said, the best grip is worth nothing, if you cannot feel the limits.
        Another point:
        All you explained makes sense to me, but it does not match with some of my personal experiences. One of the best tires on slippery concrete i ever rode is a damp cheap Schwalbe CX Comp (35mm). I’m not a fan of Schwalbe tires at all, this one if one of the cheapest, if has no fine tread, it has small nobbies at the sides, but it performs well in a couple of conditions. This performance can be observed in corners as well as out of the saddle on slippery steep uphill sections.
        How can that be?
        Is the compound mixture overriding the lack of thread optimization?

        January 11, 2016 at 7:36 am

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