When Experts Are Missing Something

hahn_shiretoko

Recently, I posted about slick tires and why they tend to offer poor traction, especially in the wet. Almost predictably, some Internet “experts” declared that it was all wrong. One of the more polite comments was: “Wow, lots of misinformation in this article.”

I guess it’s normal: If your research is breaking new ground, the results aren’t what people think they know. But the unexpected isn’t always wrong.

What the “experts” really are saying is: “This isn’t what most people believe right now. It may take a few years until it becomes widely accepted.”

Illus.BQ.RollTest

The same thing happened when we first published Bicycle Quarterly’s real-road tire tests a little over eight years ago. Back then, the idea that higher tire pressures do not increase speed bordered on heresy.

The idea that tires roll faster the harder you pump them up seemed so evident that there wasn’t even a need to discuss this. Every tire company expert agreed with this. End of story. Or so it seemed.

MarkTiretesting

We were just as surprised by our results as everybody else. But after double- and triple-checking the results by running more tests, we concluded that the results were real.

Bicycle Quarterly has two people with Ph.D.’s on our editorial team, so we know how to design experiments, test hypotheses, and do statistical analyses to ensure that we are measuring real differences between tires and not just variations in the testing conditions. (The last point is very important, yet it’s often omitted in cycling research.)

How to explain these new findings? We realized that the “accepted wisdom” overlooked an important factor: Suspension losses caused by the vibrations of bike and rider consume significant energy. With higher tire pressure, suspension losses go up, and they cancel out any reduction in rolling resistance that comes from less internal deformation of the tire.

Previous testing had been done on smooth drums, were suspension losses don’t occur. That is why the experts missed a crucial part of the equation, and their conclusions did not match the real-road testing.

Roubaix94

Test results are fine and well, but the results must confirmed on the road. Apart from BQ staff and readers, professional racers were the first to adopt our idea of running wider tires at lower pressures. On the cobbles of Paris-Roubaix, you now find many pros running 30 mm-wide tubulars at 70 psi. The days when racers used suspension forks and narrow tires pumped to high pressures (above) are long past.

And even on the smooth roads of the Tour de France, the pros run 25 mm-wide tires, which is a huge step up from the 21.5 mm tires that were standard when I last raced on the road 15 years ago. In fact, I am envious that today’s racers have 35% more air volume in their tires than I did!

velonews

And finally, even the “experts” have come around. It was gratifying to read a decent explanation of suspension losses in Lennard Zinn’s recent Velo tire test:

“If you were riding on smooth glass, higher pressure would be better. On rough surfaces, however, a tire at lower pressure is better able to absorb bumps, rather than deflecting the entire bike and rider upward.[…] The less energy is sent upward with each bump, the less energy it takes to keep the bike rolling.” 

Even though most Internet experts now accept our tire pressure research, they aren’t any more open to new ideas than they were eight years ago. I read that tire tread is purely cosmetic, because tires don’t hydroplane. (True, but tire tread isn’t there to displace water.)  That slick tires stick better, because they put more rubber on the road. Various tire experts were quoted.

Could it be that the experts once again are overlooking something? Back in 2007, they didn’t realize that suspension losses were important.

Perhaps now the idea that the bicycle tire tread can interlock with road surface irregularities is still a little “out there” – even though it’s long been known and accepted by many tire experts. (I first read about it in a 1980s paper authored by a Michelin tire engineer.) Perhaps we have to wait another eight years until the idea is generally accepted…

GravelHelens

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

About Jan Heine, Editor, Bicycle Quarterly

Spirited rides that zig-zag across mountain ranges. Bicycle Quarterly magazine and its sister company, Compass Cycles, that turns our research into high-performance components for real-world riders.
This entry was posted in Testing and Tech, Tires. Bookmark the permalink.

74 Responses to When Experts Are Missing Something

  1. Chris J. says:

    I’m certainly no expert, and I don’t have strong opinions on the relative traction of slick vs. treaded tires, though I will admit I accepted Mr. Brandt’s views on the subject for many years.

    But in this debate, unlike the rolling resistance of tires of various widths/pressures/casings, it seems we don’t yet have any good measurements, at least that I’ve seen. We have a lot of opinions, and the holders of those opinions feel they have experiences that confirm those opinions. But as with tire width/pressures, we know that the perceptions of experiences don’t always match the reality.

    The interlocking tread/asphalt argument sounds logical, and Jan has far more experience with cornering limits on various surfaces than I do. But I’d still like to see the results of some well designed quantitative experiments.

    • You are right, we don’t have quantitative measurements, because getting such measurements is extremely difficult. TOUR, the German magazine, tried for years. First they dragged a wheel behind a car and turned the tire so it skidded, measuring the resistance. It wasn’t useful. Then they built a scooter, hired a stuntman and had him corner on tighter and tighter radii until he crashed. They hoped that the tightest radius achieved for each tire would give them a value for how much grip it had. Unfortunately, it appears the results were not consistent from one run to the next.

      TOUR roller

      So for tire cornering adhesion, we have to rely on how the bike feels during cornering with different tires. That may sound unscientific, but it isn’t necessarily so. The difference in cornering ability and in the radius on which the tire corners (tighter with more grip, wider if there is more squirm/slip) are so pronounced that they are easy to notice. Science in this context is to come up with good hypotheses, create tires that allow testing them, and then try the different setups on the road.

      • Harald says:

        Seems like the link is broken. Proper link to pdf

        “Unfortunately, it appears the results were not consistent from one run to the next.”
        I don’t see that stated in the linked article. Could you say more about the source for this statement?

      • It’s based on off-the-record talks with the authors by journalist friend of mine. The scooter was never used again. It now is gathering dust in a corner of the TOUR offices.

        Of course, for mainstream magazines, publication schedules don’t often allow to just cancel an article because the testing didn’t work out. Bicycle Quarterly has a lot more freedom…

      • Harald says:

        Good to know — and too bad! The scooter seemed to have the potential for scientific testing with real-world validity.

      • Yes, I was excited about the scooter, too. I was thinking of building one for BQ. You have to give TOUR credit for trying. But if the results aren’t repeatable, then they are useless.

  2. David E says:

    An electric bicycle sounds like a better test platform for testing bicycle tires. Butt on the saddle and more speed would give more realistic results. The rider would be free to wear heavy pads and not need to pedal or foot push a scooter. Acceleration could be measured at the hub axle along with a video recording the tread to determine exactly when the tire starts to slip/skid in the wrong direction. Test repeatability is often related to the procedure and accuracy of data measurement.

  3. Al says:

    It seems a tire with tread would have more surface area to contact the road, if pressure is low enough to allow the tire to give a bit, as be the case for those of us with wider but softer tires. I haven’t the ability to prove it, but it seems to make sense.

  4. Over 45 years of cycling, I have learned that you really can’t tell most people anything. The start of any real knowledge is a Zen-like humble, “know-nothing” attitude. Most cyclists I encounter have just the opposite; they tend to be very arrogant, and very set in their ways, so it does no good to try to convince them of anything, to throw pearls before swine. And the people they WILL listen, often established pros, too often pass on established dogma. A good example of this is the oft-cited fallacy that putting all your body weight on the outside pedal while cornering will “lower your center of gravity,” a fallacy often repeated in popular cycling publications and a belief firmly held by a disproportionate share of cyclists. Determining the truth- what really happens – lets you go beyond the accepted practice and to perform at an even higher level.

    • The outside-pedal center of gravity thing is funny, because simple physics can refute it. However, we have to be careful, because sometimes the explanation (“lower center of gravity”) is incorrect, but the observation (“put weight on outside pedal”) may be correct for different reasons, like it changes the way you pull on the handlebars.

      That said, I find it best to relax while cornering and stay centered on the bike. I tried the “put weight on the outside pedal” method, and I found it distracting from feeling what the bike and tires are doing, which is so important as you approach the limits of adhesion.

      • Bill Wood says:

        Jan, I notice you don’t lean the inside knee towards the road like motorcyclists do. Isn’t that a proven way to lower center of gravity and improve cornering?

      • Motorcycle racers stick out their knee to feel where the ground is. We cannot lean that far, and we don’t have knee pads…

        Bicycles are designed to have their center-of-gravity in line with their wheels, so hanging off to one side usually isn’t useful when cornering. Fortunately, sticking out the knee has very little effect, so it does not appear to be detrimental, either.

      • I think the reason that motorcyclist hang off the inside of their machines is the likely the same reason mountain bikers try to stay on top of their bikes while cornering – to keep as the centre of gravity as much above the tires as possible (increasing traction by keeping force as close to perpendicular to the road as possible). The difference is that on a motorcycle, the bike weighs much more than the rider. The same is not true on a mountain bike. I have no concrete evidence for this think, though.

      • Motorcycle handling is complex, but as you say, the machine is heavy, so throwing it from side to side isn’t as easy as it is on a bicycle. For those interested in motorcycle handling and dynamics, I highly recommend Tony Foale’s book “Motorcycle Handling and Chassis Design: the art and science”.

  5. nickskaggs says:

    “Because when it comes down to it, I’d rather be riding than discussing bikes online.”

    Uh oh. Sounds like being cooped up with an injury started to get to ya…😉

  6. Matt says:

    Jan,
    Could you please talk a bit about rim width and how this effects the shape of the tire and it’s stability in corners. It is an often overlooked aspect of this topic.

  7. “Internet experts” are part of the fabric of the cycling community. They (am I one? certainly an enthusiast who replies to the blog . . .) ultimately have the best interests of cyclists at heart, but can be misled or dogmatic. This transfer of ideas is ultimately good for cycling, however. It would surely be trying to have your findings ruthlessly questioned, especially when they are evidently clear based on your experience.

    Speaking of expertise, there is a whole new generation of “mainstream” bikes (other than the diverge) which would make great test candidates, and good reading. Cannondale (650b lefty allroad bike), Trek, (720 920) are a few that stand out to me and I would love to read a test of one.

  8. Chuck Davis says:

    Some years back Cyclist had a Q & A involving Jim Mertz from Specialized, J Brandt as a consultant for Avocet, Arnold Van Ruitenbeek and Horst Vogt, engineers for Continental, and Mathew Aaron for Michelin re “How To Buy A Tire”
    Gen on the matter of tread, or no tread, all were pro no tread

    • It’s understandable that people repeat what they hear from the industry, but the consensus sometimes changes when the old ideas are shown to be wrong.

      If the question was asked a few years ago, I suspect the industry experts also would have said that higher pressures roll faster. And that narrower tires are faster. Today, few industry experts will still say that…

  9. Jon Gehman says:

    As good as it is for cycling in general for some of this information to work it’s way into the mainstream, I’m a little sorry to see more and more people come around to the idea of wider tires and lower pressures. There’s a few younger guys I’ve been keeping up with(thanks to your tires),that are coming around to better tires and I’m wondering if I’ll be able to hang with them next spring, and a few of the riders my own age that I’ve been handling pretty easily might now make it tough as well.

    Please come up with something else that no one else will believe for a decade or so that will help old guys like myself…

  10. Matt says:

    The idea of a fine tread such as that found on the Compass, Challenge, and Vittoria tires, to name a few, makes good sense to me. It reminds me of of our own finger prints and how they enhance our own gripping power. Or the directional texture of a dogs pad, it’s optimized by tens of thousands of years of evolution. I wonder how a MTB tire that had the same general design would perform with highly textured “pads” .

    • Alex says:

      – or the toe pads of a Gecko . . . that actually improve with humidity (but don’t work at all under water . . . ) can we engineer van der Waals forces into bicycle tires?

  11. Francisco says:

    One thing I have noticed in the Tour testing is that German or Austrian brands usually tend to come out on top. Rather than accuse the magazine of bias, I think there is a natural selection process here: (1) an influential magazine with a large readership starts testing bikes, frames or tires against some quantitative criteria they have dreamed up; (2) the brands that target that readership will make a special effort to optimise their products to do well in those tests; (3) these brands become consistent Testsieger; (4) market segmentation is reinforced along the language divide.
    The funny thing is: my own experience often starkly disagrees with Tour’s rankings. I’m not referring to stuff such as rolling resistance, that cannot be evaluated properly by feel; but rather things such as resistance to cuts and punctures or behaviour close to the limits of adhesion, that we get to know quite well empirically.
    The quality of objective testing seems to be bound by the quality of the underlying criteria and methods.

    • You are right, there is no ill intent – it’s simply a matter of “designing to the test”. In an interview, the TOUR guys noted how the German mail order company Canyon designed their bikes to TOUR’s test and then won every comparison test against Italian brands like Colnago that cost many times more. They thought it was a great thing, proof that their tests were improving bikes.

      However, in their quest to be “objective” and quantifiable, TOUR may have lost sight of the fact that their tests may not represent real-road experiences. For example, all their bikes are evaluated based on their “stiffness-to-weight” ratio… but nobody has shown that the type of stiffness TOUR measures actually makes the bike faster or more fun to ride.

  12. Bob C says:

    While I find the question of tread vs. slicks interesting in an abstract way (and for the record, my intuition is on your side, Jan) when it comes to this topic, aren’t we really talking about extremely marginal gains?

    Most of us do not corner at the limits of adhesion for a lot of good reasons (road debris among them!) and most of us don’t measure the success of our accelerations in microseconds. It seems to me — without research, naturally — even if tread provides more traction, for the vast majority of real-world riding isn’t the expected benefit is vanishingly small?

    Answering this question is unlike the work you did on tire width and pressure — which was extremely important and made a big difference for all riders in real world settings (bless BQ for this work!).

    All of that said, I feel Compass tires are without peer and have massively improved my riding life. So if you feel it will make them even better, by all means go for it!

    • It’s hard to say for whom performance differences are important, and for whom they aren’t. I feel that if your bike corners with more precision because the tire slips less, that is a good thing even if you aren’t at the limit of adhesion. It’s easy to dismiss a piece of high-performance equipment as “only necessary to gain the last tenths”, but in reality, the better equipment is more fun at any speed. And a great bike is made of small (and sometimes large) gains in many areas. Most of all, it doesn’t cost more to make our tires with the tread pattern that seems to work best…

      (Background: Tires always slip, but usually the slip is so slight that you don’t notice, unless you drive a car in a parking garage and notice how much the tires squeal even at low speeds.)

    • marmotte27 says:

      I’m a pretty average rider and I don’t think I’d win any medals for my cornering speed. Still I managed to crash twice while cornering with a treadless tire (I cannot of course be entirely sure that it was the tires fault in either case, especially as I don’t even remember the second crash…). Switching to Compass tires, knowing that they have that great cornering ability, has at least given me back some peace of mind and confidence on descents.

  13. Bryan Willman says:

    Another serious problem with grip testing that the road changes quite a lot. Car and Motorcycle racers talk about a track “rubbering up”, how the grip changes as rain cleans rubber off, or as running vehicles put rubber back.
    Some tire compounds are not “compatible” with each other.

    So testing bicycle tire grip will be fraught – in fact, simply repeating the test many times on the same surface patch may change the answers, as the testing may “rubber in” the test patch!

    What’s more, a road right after a hard rain, a road that is wet, a dry but rubbered in road, may well give different results.

    To add to the fun, a tire with very high compliance may not gain so much from side treading, while a tire that is “stiffer than optimum” might gain quite a bit. (Oddly, the tires I’ve seen with side tread are high quality very high compliance tires…)

    • You raise a good point – the test surface may change as a result of the testing. So perhaps TOUR should have pressure-washed the test surface after each run! Add to that the need to keep the temperature constant (both air and rain water) and to run tests only when there is no wind, and it gets terribly difficult to do meaningful testing.

  14. Michael says:

    I’m looking forward to the wide tire testing to see how they compare to the fastest tires of the earlier BQ tests. We’re Hetres ever tested against the fastest 25’s?

    Also, can someone define this “real world riding” concept? Doesn’t everyone ride on the same pavement, no matter how they use their bikes?

    • We did test Hetres. They were fast, but of course, their longitudinal tread squirms and slows them down a bit. So we made the Compass Babyshoe Pass with an optimized tread.

      “Real-world riding” means that we ride anywhere, anytime, for any purpose, not just for short jaunts on smooth pavement and sunny days. So it means that our bikes need good fenders, lights, as well as the ability to carry some clothes and other things…

  15. Pingback: When Experts Are Missing Something | Kite*Surf*Bike*Rambling

  16. Mike bike says:

    It seems to me that the TOUR test is not totally inconclusive even if they were not able to find a statistically significant result with tire tread. What I conclude from their experiment is that tire tread is not a statistically significant variable. Turning technique, road surface, balance, or other hard to define variables probably play a bigger role in keeping a tire from slipping that tire tread pattern. Meaning that tire tread pattern probably is a secondary or at least not a primary variable in determining cornoring grip in a turn.

  17. John Duval says:

    With bicycles we don’t talk much about other tire behavioral characteristics, like slip angle (referring to the difference between direction of travel and wheel angle in a non-slipping condition). For example; one tire might take just slightly more steering input to balance or initiate a turn, while another may wander a bit in a corners as if the tread were not coupled to the rim quite so well. But seldom are such complaints mentioned (other than the crabbing of knobs). Maybe because bias ply tires don’t vary much in those characteristics.

    Every few years a radial bicycle tire comes out promising lower rolling resistance, higher mileage, better grip, and more comfortable ride, but they also have a reputation for a sloppy feel. Soft sidewalls alone do not explain it. At least the idea is enough to make me wonder about the angle of the cords in bias ply tires, and other layers often added under the tread for various reasons. Do these offer potential performance benefits to bicycles?

  18. Ed B says:

    Since December of 2015, I have observed three Randonneuring crashes due to incorrect steering input and this is only on my last five Brevets.

    Thinking of it, most Randonneurs corner quite slowly and I have never seen a fellow Rando lose adhesion on a corner (w/o sand) but I have seen two crashes due to the rider clipping the curb. Quite a lot of cornering crashes on Brevets in my opinion. Better tires would not have prevented any of the at least six cornering crashes that I have observed in my last 12 months of randonneuring. Might be that poor lighting is a bigger concern?

    In my opinion, we’ll never get good data on the subject at hand (better cornering adhesion).

    But a simple test for anyone might be to mount narrow slicks at 115 psi and do some sweepers on your favorite bumpy corner. Find the speed where your comfort level diminishes. Yes, this is subjective but everyone will have a comfort level. I am not talking crazy fast, just the speed where the corner gets your attention. note that speed. Then mount some 32 mm Compass EL tires at 60-80 PSI and repeat the corner at the same speed as above. If this test does not turn the Unfaithful into Believers, nothing will. On a very hilly 200K this fall, I had decided to do the ride fast and selected a road bike with 25 mm Vittoria open cx iii tires. These tires generally corner well; however, the riders on wide 650B tires and the other wider tire riders just went away from me on the tricky descents. I was absolutely at the adhesion limits of my machine while they were casually making their way down the road with ease. I am normally on my brakes with these guys when on my “rando rig”.

    If tread pattern does not matter, why did Schwalbe put a tread pattern on their newest, latest uber-ultra-special S-One, Pro One and G-One tires?? Maybe a realization that our road surface quality is less than optimal and some interlocking connection between the surface and tire does exist on sub-optimal road surfaces??

  19. mike says:

    I’m not that interested to hear that with tire A it is possible to corner 3% faster that with tire B – evaluated by a test using a scooter or something similar to find out the real max. speed.

    The max. cornering speed I can achieve is not the max. cornering speed of the tire. It’s the speed at which the tire makes me feel, that I’m near the limit. I have ridden tires where I never found out their limits because I couldn’t develop a clear feeling for them. Maybe their grip was that bad, maybe I was just to anxiously to push them further?!
    In fact that makes no difference – I was slow with those tires.

    If you tell me that a special tread can make it happen, that I can feel if I’m on 80% of the limit or on 90% – than I’m really interested😉
    The development of a good feeling at the limits also could be a useful function of fine thread …

    • Your point is a good one. I think the main thing for developing a good feel for the limit is to run wider tires at lower pressures. At 80 psi or more, the tire feels like it’s skating across the surface, giving you little feel for how much grip you have. And of course, there also is less grip, because you are not interlocking with the road surface much, since the tire is too hard to conform to the road irregularities. For all those reasons, wider tires descend much faster than narrow ones. Perhaps that is the main reason professional racers are moving to wider tires, in addition to the small improvements in rolling resistance.

      As to tread patterns and cornering feel, it appears the less slip you have, the better your feel. If your tire slips or squirms, you are getting the sensation of grip running out, even if there may be some in reserve… So perhaps the tire that provides the most grip also gives you the best feel. Many users of Compass tires report that they corner faster than on other tires. That may be the supple casing (better road surface contact) or the tread pattern – most likely both.

      • mike says:

        Hmm, it’s not only about width and pressure. I had 2 crosstires with identical width and used the same pressure. But one abruptly lost grip going up on slippery ground while the other introduced its limit very well. It’s like an old Porsche 911, who might corner faster in total, but you may be able to be as nearly as fast but with ease with a Lancia Fulvia ….

      • I was talking about road tires. Of course, in mud, tread pattern plays a huge role! Especially how well the tire clears mud is of great importance…

  20. Archetype says:

    Reblogged this on The Road to Revelation and commented:
    Once again Jan Heine and the bicycle quarterly staff have provided sound, in depth research and tire test results.

  21. Ed says:

    The problem i see is not entirely about closely held beliefs it is about less than concise reporting. Case in point, the blanket statement ‘lower pressure means lower rolling resistance’ is a incomplete statement and often incorrect but that is what was headlined and reported. The crucial missing information was ‘on uneven surfaces’. Now the blanket statement du jour is ‘slicks corner better’ and here we go again. A report on a complicated subject can only be simplified so much before the simplification becomes incomplete and erroneous.

  22. Ed B says:

    How many of us ride on “even surfaces”? You know. The ones where tread does not matter. Continental, Schwalbe, Vittoria, Michelin, Veloflex and others are designed in places where road surfaces are uniform and even.

    Bumpy, unevenly applied chip seal and rutted roads are my norm.

    Some tires feel more secure handling on my normal roads. Tire selection and even tire pressure takes some thought if overall optimization is a goal. The transient, dynamic nature of cornering a bicycle on real world roads is complicated especially if data is required. But it isn’t. Ride quality differences between tires can be felt. My hands are still numb from PBP because I did not ride my 32 mm Compass extra legere tires. The cornering confidence between my various 25 mm tires and my 32 mm Compass tires is really, really obvious to me, whether due to a combination of tread, casing, rubber compound, pressure, tube type (latex or butyl) or just better suspension owing to more air. No data is needed for me. I feel it. Is any tire more comfortable overall than my latex tubed 32 mm Compass Stampeded Pass in extra legere casing. YMMV.

    One of the nicest aspects of wider tires for me at least is not needing to pick my line thru a bumpy corner and when fatigued, this confidence or security is of great benefit. I think/feel that tread plays some role on these real world road surfaces.

    Leonard Zinn at VeloNews received some interesting opinions from tire manufacturers on the effect of tread patterns…mostly about overall wet road behavior but lots of tidbits on dry roads, too.

    http://velonews.competitor.com/2014/05/bikes-and-tech/technical-faq/technical-faq-tire-grip-wet-conditions_328827

    • How many of us ride on “even surfaces”? You know. The ones where tread does not matter.

      It appears that at least on paved surfaces, tire tread can improve grip, no matter how smooth the road is.

      Beyond that, some surface roughness is desirable for safety. I read somewhere an article chastising “certain contractors who took pride in how smooth they could make the road surface”. You need some surface “grain” to improve tire grip.

  23. Treharne says:

    Geckos offer a very good biological homologue to this debate. They can walk upside down on smooth surfaces and they do not use slick toe pads. Google a pic. They are heavily and deeply treaded. Likewise Ice tires for cars are heavily siped for getting traction on ice. The reason race cars use slicks is that the compound is so soft it conforms to surfaces, however, race tires last one race (or not even).

  24. marknreimer says:

    Agreed regarding the motorcycle comparison – every motorcycle handling book I’ve read, /video I’ve watched and course I’ve taken has indicated dropping the knee is a big ‘no’ unless you’ve got the skill to drag it on the concrete. It’s got nothing to do with lowering the centre of gravity. The knee drops primarily to use as a gauge for how much more you can lean the bike. Some use it as an air brake in high level competition, but that is secondary at best. If you aren’t so close to the edge of traction that you must check the ground clearance with your knee, there is zero reason to stick it out. In fact you’ll do more harm than good by upsetting the balance of the bike. Same with cycling. Curious that it seems to be such a natural reaction by many riders though.

  25. Tom says:

    Sorry for beeing honest:
    So much text just to say: “I believe, I was right with the pressure theory (which was not at all new to anybody who has been racing), so people not believing me in the “thread theory” are just not yet ready for this new knowledge”. Not much of an argument, sorry.

    • which was not at all new to anybody who has been racing

      It’s nice to see that the idea that lower pressure doesn’t make a tire slower now is so widely accepted that it’s “not at all new”. I raced for many years, and I can tell you that we pumped up our 21.5 mm-wide tubulars as hard as we could, since we wanted to get that last ounce of speed!

      • Bob C says:

        Yes, high pressure was absolutely the orthodoxy for decades and it would be a mistake to presume otherwise. And so were narrow tires — I remember well how people arguing for the radical change to 25mm tires in the late ’90 and early ’00s were pilloried in racing circles. God help you if you went to 28mm — you’d never keep up (people thought!)

        While I believe the tread issue is harder to resolve (and I suspect relatively trivial ultimately) I think the work that Jan and BQ have done on wide, low pressure tires is a major contribution to cycling in the last 20 years. It’s a big deal and we owe you a debt of gratitude for the research, and then for the tires that came from it.

        We’re having more fun, greater comfort, greater safety and, yes, speed because of this work.

      • Ed B says:

        I used to crank the 19 mm Conti tubulars to 180 psi for time trials. Never flatted but had some interesting cornering experiences at the turn around.

        Fat 22 mm tubulars were for road races. Only 130 psi

      • Tom says:

        So you even invented, what we used already in the early 90ies? Less pressure an rough roads, not more than 8bars if it’s not a time trial an super-even surface – and now that’s not true until you fnally wrote it down?
        Funny by the way, that the only argument you are willing to add is: “But I believe, I was right with the pressure issue”.
        All over the world rubber tires are chemically designed to be soft enough to “grip” the road surface. If there was tread pattern needed to “grip”, bike tires could be made from hard plastics. And if sufficiently soft rubber would wear quickly by beeing too soft – how quickly would treads wear?

      • I am sorry we have a misunderstanding about what “low pressure” is. You talk about 8 bar (116 psi), and you are right, many riders used that type of pressure in the 90s and before. However, these days, 116 psi is definitely considered high pressure.

        Even many pros now run their 25 mm-wide tires at 80 psi (5.5 bar). And our 42 mm-wide tires roll as fast at 40 psi (2.7 bar) as your narrow tires do at 116 psi, even on super-even surfaces. We tested them on the smoothest asphalt we could find – the inner apron of a velodrome.

        I think you’ll agree that nobody believed until very recently that the same 25 mm tires could roll as fast on smooth asphalt at 70 psi (5 bar) as they do at 160 psi (13 bar). And some probably still don’t believe it today.

  26. Jose Almeida says:

    After reading the thread, I thought the test I ran on this subject might be of some use for some, and none for others.

    I grabbed my All Road/Gravel/Monstrosity or whatever the scene is calling it these days, too fast of a pace for me to keep up, went for a light touring trip to Japan with a couple of mates and climbed Mt. Fuji. For what u might ask!? To rip down those switch backs as fast as I could. I was on board my bike fitted with a set of Compass Barlow Pass 700x38c Extralight.

    I made the descent of roughly 2500m vert, and 45km in under 45m, make the math. Only touching the brakes on the most pronounced switchback’s, every other turn was made simply on tire grip and a good tuck, at some stage I’m sure I heard the bang of Sound Speed Barrier being broken.

  27. Jose Almeida says:

    My terms of comparison happened when upon arrival back home I grabbed my Road Training bike, fitted with 28c slick tires, went for a spin with one of those mates on our regular training route. Went for it on a downhill corner, with the added confidence acquired with the Barlow Pass tires, and was sent on a two wheel slide into oncoming traffic. Somehow was able to pull her back underneath me and safely return to my lane. Only damage was a brown spot on my mates Chamix that was being me looking at the action unfolding at the time.

    Has I said very scientific data.

  28. Bill S says:

    I’ve not seen this aspect adequately addressed, though I know Jan has mentioned it in other posts: rubber compound has a greater effect on overall traction and corning speeds than tread or lack there-off. That said, I’ve been riding 700×25 Conti GP4000 slicks for 8 years in all kinds of weather on all kinds of paved roads, often in the mountains in rain. Never had an issue because I run lower pressure if I know it will be a wet day. Only complaint I ever hear on GP4000 is shallow cuts due to softer compound. Vittoria Open Corsas with file tread use even softer compound, have many more cuts and typically are done well before 1000 miles, at least with the guys I ride with. A couple of those guys are now running Schwalbe One Pro, but nothing definitive on those yet.

    On non-paved surfaces (or even rough chip-seal) I can see how even a file tread could help, but in my mind, tire pressure is a greater differential than what minor tread a road tire may have. So what of the new Soma Vitesse that is half file, half slick? Jury still out since it is new.

  29. Bill S says:

    Interesting to note that in comparison to Jan’s article of 2012, “Why Don’t Racers Use It?”, so many major bike manufacturers now produce road bikes shod with 25mm and even 28mm road tires. Even a few now have wider (22mm+) rims that allow a 25mm tire to measure 27mm! Would most riders have even given that a thought 7-8 years ago when Jan first gave attention to the aspect of wider tires? In a way like going back in time, when 27 inch wheels were shod with 1.25 inch tires…..only that combination was quite heavy compared to the modern stuff. Quite common these days: 35 mm tire on 25 mm wide rim, with wheels weighing at under 1600 grams (rider limit 210 pounds). Me thinks this is the New Golden Age of bicycles!

    We are spoiled indeed…..

    Cheers,
    Bill in Roswell, GA

  30. Tom says:

    Jan, I think we do have another misunderstanding there:
    “I think you’ll agree that nobody believed until very recently that the same 25 mm tires could roll as fast on smooth asphalt at 70 psi (5 bar) as they do at 160 psi (13 bar). And some probably still don’t believe it today.”
    Au contraire – I think, nobody doubted, that there is an optimum in pressure depending on tire width and surface unevenness. There is even a term in Europe of a “tire pumped to death” for a bad rolling tire due to too high pressure. The optimum for thhe standard 21 to 23mm tire may very likely be in the range oof 8 bars – which has been a usual pressure for many many years.

    There have been wider tires with lower pressures on bad roads (i.e. Paris Roubaix) for decades also.

    All, I am trying to point out, is: There has been a consciousness of “optimum tire pressure” for decades. The only new point is “wider tires at a lower optimum also on even surfaces”.

    BTW: Your wrong with the tread-idea anyways, even if you still avoid to answer any point concerning “style of argumentation” or “content of postulate” in the tire-tread-discussion. Show a physical proove, that race style bike tyres (like michelin ProRace or Continental GranPrixX0000) are too hard to provide physical grip by forming a junction with road surface – and there will be a profound discussion😀

    • There has been a consciousness of “optimum tire pressure” for decades.

      There used to be a consensus – the 8 bar/116 psi you mentioned in your earlier comment was pretty universally accepted. Then came new research, and suddenly we are having pros run 5.5 bar/80 psi. I think you’ll have to agree that that is a pretty big change.

      There have been wider tires with lower pressures on bad roads (i.e. Paris Roubaix) for decades also.

      I don’t think you can name a single rider who used 30 mm-wide tires in Paris-Roubaix from 1970 until 2010. Back then, “wider tires” meant 25 mm. Now that is “narrow”, and wide is “30 mm” or more. Again, that is a pretty big change.

      Your wrong with the tread-idea anyways […] Show a physical proof…”

      Just because something is difficult to test doesn’t mean it’s not true. Most bicycle engineering has been not through “physical proofs”, but through riding bikes with different components. And anybody who has ridden our Compass tires reports that they grip extremely well, better than other tires with the same tread rubber. It’s not “physical proof”, but all I am asking is that people like you are open to the idea, rather than say “It’s not what we know, therefore, if cannot be true.”

  31. Ben Hudson says:

    Would you expect wider, lower pressure tyres to be an advantage for track racing? I know you’ve tested tyres on the track apron, but what about on the track itself? I assume that very large tyres are no good due to aerodynamics, whereas comfort and fewer suspension losses on the road at lower speeds far outweighs this. But it would be interesting to know what size and pressure is fastest in this very constrained environment…

    • We found that on smooth roads, tire performance levels off at 25 mm. That means that wider tires aren’t any faster (but also no slower, at least up to 31 mm, we haven’t tested wider ones yet). Since wheel weight matters a little on the track (but not all that much, otherwise, they’d all use the smallest allowed wheels), track riders might be fastest on 25 mm tires (as wide as necessary, but no wider). I read a few years ago that some teams had switched to that width.

      I don’t follow track equipment closely enough to know whether that switch was permanent or temporary. For racers, confidence is a huge factor, and if something feels different (and perhaps slower due to the reduced frequency of vibrations), it may put the racer at a disadvantage, even if it is marginally more efficient.

  32. SteveP says:

    Slightly off-topic but there are other effects of tread pattern. I used a set of Panaracer Gravel King tires on a recent French tour. Part of that was along canals and other “velo routes”. surfaced with fine gravel.

    The Gravel Kings were fine, but the tread was just the right pattern to pick up the finer stones and continuously fling them against my fenders. It was like being chased by machine gunners🙂 Maybe they need to offer them in fine, medium and coarse.

    • Tor says:

      Actually, that (with water) is another less obvious (until you ride it) benefit to slicks mentioned by Jobst Brandt. The slick tire will pick up and throw much less of whatever is on the road than any tread will throw. The fine, medium, coarse distinction means that on a long ride you’ve got to make your guesses and hope for the best – and the additional tires to stock and all that will drive up the price. If the tread is proven to mean a real gain in slip-out angle (by repeatable experiments), then perhaps it is worthwhile, but until then I remain skeptical.

      • A well-designed tire tread won’t pick up rocks and debris, either. I don’t think you’ll notice a difference between slicks and a Compass tire when going over gravel in that respect.

        On a wet road, the “rooster tail” behind a slick tire actually is larger than it is behind our tires. It’s easy to observe this. I think the reason is the center tread on our tires, which has longitudinal ribs and allows for a little water displacement, so not all the water is thrown up.

        When going through puddles, it appears that our tires do throw up more water. There, it appears that the angled shoulder tread picks up water that a slick tire might not. But that is what fenders are for!

  33. Tor says:

    Hmmm… Jobst Brandt may not have been always right, but with a substantial mechanical engineering background and a few hundred thousand miles of hard riding on just about every terrain imaginable he was seldom wrong. By the archives I’ve found, he also ranks high on the list of experts at high speed cornering – done on slick tires.

    I’m not certain you are wrong, but nor am I yet convinced you are right. It might not be easy to get reliable hard data on how tread pattern effects traction, but one thought that crosses my mind is to see if an inker could be attached to show any differences in the actual tire contact with the road.

    Another thought that crosses my mind is to wonder if there is a slight walking effect from the file tread that provides the feedback on traction (offering psychological comfort at higher speed) with minimal real effect on actual slip-out angle. Somewhere in the yarchive.net postings Jobst mentions that a (very?) fine “tread” does not appear to have a detrimental effect on traction.

    Ultimately, I’m inclined to suspect that the way to resolve this is tilted treadmill tests where the angle can be verified with accuracy and the tires can be taken all the way to slip-out without shedding blood.

    • Jobst Brandt may not have been always right, but […] he was seldom wrong.

      Jobst Brandt was a great guy, and it’s not lightly that I disagree with him. But as you say, he wasn’t always right. He remained convinced that higher pressures make tires roll faster – the flame wars back in 2007 on “rec.cycling.tech” were something else!

      I heard through through a friend of Jobst’s that Jobst believed tire tread didn’t matter, because the tubulars he was riding gripped well even when they were worn smooth. He appears to have overlooked that the tread on the edges of a tire doesn’t wear. (And even Jobst wasn’t strong enough to spin a tire when accelerating in a straight line!)

      If Jobst were alive and healthy, I suspect he’d change his views on quite a few things as new evidence emerges. His contributions were great – he brought the idea that thinner spokes make stronger wheels into the mainstream.

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