Why We Don’t Make “Gravel” Tires

pub_compass_mexico

At Compass Cycles, we love riding on gravel roads, so it may come as a surprise that we don’t make “gravel” tires. Compass tires are road tires, perfected for use on paved roads. The rubber compound is optimized for grip on pavement, and the “chevron” tread pattern interlocks further with the road surface. Everything about our tires is optimized for performance, both in a straight line and around corners, in dry and wet conditions.

switchback_hill

So why do gravel racers love our tires? Because they are supple and ultra-fast. What about the “road” tread? Wouldn’t you want knobbies for riding fast on gravel?

The truth is that on gravel, knobs don’t make any difference. Without semi-firm ground to dig into, knobs can’t do anything. When you slide, it’s because gravel is sliding on gravel, not because your tires are sliding on the top layer of rocks.

quattro_slicks

Rally drivers made a similar experience. During the early 1980s, they found that, to their surprise, the slick tires they used on the paved roads were faster on gravel than tires with more tread (above). Even though slick tires aren’t allowed on rally cars any longer for a variety of reasons, the lesson may remain valid: On gravel, tread patterns make little difference.

For bicycles, what makes a good road tire also makes a good gravel tire:

  • Supple casing: on the road, this gives you speed and comfort. On gravel, the same still holds true, but it also gives you traction, because the tire conforms to the surface, and thus has more grip. (One advantage of the rally cars’ slick tires was that they were super-soft.)
  • Large width: On smooth roads, more air just means more comfort. On rough roads and gravel, it also means more speed, because your bike doesn’t bounce (which loses energy through suspension losses).

The same features that make our tires perform so well on pavement also make them great on gravel. We’ve resisted the temptation to add knobs for a more “rugged” appearance. Instead, Compass tires offer you the best performance on a variety of surfaces. That is why we call them “Allroad” tires.

If knobbies don’t help on gravel, why does Compass now offer a knobby tire?

steilacoom_sx

The answer is simple: mud. When it’s muddy, knobs dig into the surface. You get more traction, because a knobby tire needs to displace much more material to spin. We designed our Steilacoom knobbies to offer good performance on pavement, too. In fact, first tests show that they are faster than any knobby we’ve tested, but they’ll never equal the performance of our “Allroad” tires.

elk_pass_gravel

What about flats? Shouldn’t a gravel tire be reinforced to fend off flats?

It depends. Punctures are less likely on gravel, because the tire pushes sharp objects into the (relatively soft) ground. On pavement, the hard road surface forces the object into the tire. That is why punctures from glass or nails are rare on gravel.

Sidewall cuts from sharp-edged rocks can be a problem for some riders, and many “gravel” tires have reinforced sidewalls. But that also makes them slower, less comfortable, and reduces their traction. Cyclocross racers have ridden on high-end tubulars with very supple (and unprotected) sidewalls for decades. And many gravel racers use Compass tires without suffering from cuts. It really depends on your riding style – experienced cyclists usually ride “light” and let the bike move under them. They usually suffer from few problems. Tire pressure also plays a role. If the pressure is too high, it’s easier to damage the sidewall. A softer sidewall deflects as it hits a sharp rock rather than getting cut.

dirt_road

Just before winter snow closed my favorite roads last November, I was heading into the Cascades to explore gravel roads on a 700C test bike for Bicycle Quarterly. As I set up the bike for this challenging ride, I had to choose betweeen knobbies and road tires. My decision was easy: Road tires roll much better on the paved portions of the ride, while giving up nothing on gravel. They were an obvious choice.

But now I am plotting a truly muddy ride, so I can take our new Steilacoom knobbies for an adventure, rather than using them only for cyclocross…

Click here for more information about Compass tires.

Addition (2/21/2017): Several rally experts have questioned whether early-1980s rally cars used slick tires on gravel. At the time, it was reported in the German magazine Auto, Motor & Sport, but the use of slick tires on gravel may just have been isolated to a few rallies. Shortly after that report, the rules of rallying changed, and slick tires no longer were permitted, either on gravel or pavement.

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.
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97 Responses to Why We Don’t Make “Gravel” Tires

  1. Willem says:

    I love my Rat Trap Pass Tyres, but they do have their practical limitations as soon as trails are wet. The problem is not so much wet gravel, but wet soil. Where I ride there are many trails that will not have much gravel, but a sandy surface that gets slippery when wet. Wet leafs are similarly treacherous. This is not to say riding the Rat Trap Pass there is impossible, but it does demand finesse and a cautious attitude.
    There is not one simple answer to all this. With friends I made a loaded tour in Norway a few years ago. We hesitated what tyres to fit. Some of us fitted almost slick Schwalbe Big Apples, but I decided on Schwalbe Marathon Extremes. Those on Big Appels were decidedly faster on tarmac. However, the tour also included long stretches of gravel, stones, and often wet. There was no doubt that on those stretches my Marathon Extremes gave rather better traction, and were safer. The Extremes (sadly discontinued) were a nice compromise for such conditions: wide (50 mm), quite light (about 600 grams), relatively flexible, and still pretty sturdy, plus modest knobs.
    By and large I agree with Jan, however. Very wide slicks like tyhe Rat Trap Pass will get you a long way. Thus far, I have not yet had a flat with them. As for flats in cyclo cross: yesterday’s world championship was a sad story, however, with one of the top riders suffering four flats in one race. The winner had chosen a set of old sturdy tyres instead.

    • 47hasbegun says:

      I believe Schwalbe billed the Marathon Mondial as the successor to the Marathon Extreme. They also now have the Marathon Cross and Marathon GT 365, which are more aggressive than the Marathon Mondial.

  2. STS says:

    Jan,
    while I can’t really speak for rallye cars since I very unfortunately never made my move into that fascinating sport, I can certainly speak for mountain biking and gravel riding. And according to my experience with many different tires it surely makes a difference whether I ride a tire with minimal tread, a file tread for instance, or a more pronounced tread like the one the WTN Nano 40c TCS or the Clement XPlor MSO has. The difference is more than just tangible be it when climbing out of the saddle, braking hard bombing down a fire road before the next sharp turn and also in turns with regards to “lateral” traction. While the minimal tread tires most of the time feel a little faster in a straight line the overall speed especially on routes with curvy gravel descents is higher on the MSO. And the stability limit is not only higher they typically also behave more controllably when they finally skid.
    As always the design of the tread does matter. Being good on gravel certainly requires a different tread design than being good on soft soil and I can see how your Steilacoom tire is probably a good choice for mud.

    • My experience – and that of many gravel racers – is different. In the Otaki Mountain Bike Race in Japan, I was riding with top-level amateur racers (for a while), and I was surprised that on my amost-smooth Rat Trap Pass tires, I cornered at the same speed as they did on their knobbies. Of course, mud is a different matter, and I can see an aggressive tire cut into deep soil, too, but on gravel, it’s just rocks sliding on rocks, not your tire sliding on a clearly defined surface.

      An extreme example is sand. When I worked at a desert research station in the Namib Desert as a student, they were running 4×4 pickup trucks with airplane wheels and tires. Zero tread (apart from longitudinal grooves that won’t help with traction), but lots of floatation, was the best solution for driving on loose sand.

      • STS says:

        Thanks, Jan,
        there we’re facing that amazing phenomenon again: Two cyclists thinking that they are talking about doing the same thing but obviously doing things different enough. I’m sure your experiences are like what you described. But I still wanted to comment that those are not universally true. And your explanation of “gravel sliding over gravel” is probably just to simple to explain what’s going on in gravel turns.
        Maybe it has to do with me being heavier (80 kg) than you and only riding 40 mm tires on my gravel bikes. Or maybe my riding terrain is so much more demanding with regards to the roughness of the “roads”. Or maybe I’m just going even faster? We will never know until we find the chance to do some rides together.
        But our “user profiles” surely must differ discernably since I could also only shake my head in (initial) disbelief when reading that you did not encounter a puncture in 15 years of gravel riding when riding tires without any puncture-preventing guard. I wouldn’t manage to do four weeks on those tires without the need to stop and repair a tire even when riding them tubeless with fresh sealant, inflated as low as possible and everything else optimized.

      • You are totally right, different riders have different experiences. However, more and more top gravel racers are using Compass tires, because they also find that knobs don’t make a difference. Nate King from Above Category placed 16th among all the professional in Grinduro on our Snoqualmie Pass tires. Check out his video here:

        https://www.instagram.com/p/BLXgLm1Aaas/?taken-by=kingthenate

        As to your punctures, what causes them? Nails, glass, thorns? I do get pinch flats when going very fast on very rough terrrain – in the Autumn issue of Bicycle Quarterly, we wrote about “underbiking” on 42 mm tires on the “Lost Pass” in the Cascades – but no punctures.

      • STS says:

        Thanks again, Jan,
        I have always appreciated an open-minded discussion but now in the time of fake news and post-factual times I enjoy it even more.
        While I haven’t tried out Compass tires for gravel riding so far I’ve tried out several high performance (read high TPI count, speed-optimized, supple) tires when I picked up that variant of our sport four years ago after being a mountain bike and road racer for more than 20 years. Nearly all of them failed quickly and catastrophically. Most of those failures were torn carcasses. Not predominantly at the sidewall but also somewhere in the middle of the tread obviously from hitting a sharp rock too hard. Right from the beginning my approach was that I want to be able to descend as fast as possible whilst choosing the best line and not hold back because the gravel bike is not capable of doing so safely. If I found that I had to hold back in the descents than I would rather ride my mountain bike. It turned out to be not necessary with the right tires for that job.
        Most “punctures” I see when using high performance tires without any protection belt are carcass tears or ruptures rather than your more conventional puncture of a goat head or something like this. Those tears might only be some millimeters long but evidently the sealant can’t heal those.
        I’ve had amazing success with regards to puncture-avoidance with the Specialized Trigger Pro 2Bliss in the 38 mm version. It features a bead-to-bead puncture protection belt that also seems to reinforce the carcass considerably. When testing carbon rims for one of the companies I work for I lowered the pressure even further to provoke bottoming out in order to find out how those rims handle that abuse. I was amazed that not only the rims turned out to be bomb-proof but I also could not make those tires fail.
        Normally a protection belt like that effective makes a tire so stiff that I don’t like to ride it. It feels stiff, uncomfortable and slow. Not so with that Spec tire. While I notice a little difference it doesn’t really disturb me. If Specialized offered a tire with a more grippy tread – the Trigger only has a file tread – on the same carcass that would be the ideal choice for my application.
        I agree though that choosing wider tires would be better for my hard-core usage but I have yet take the time and design my next custom gravel bike frame offering ample clearance for at least 53 mm tires.

      • I don’t think anybody claims that I ride slowly on gravel, nor do the other members of the “BQ Team”. The only puncture through the tread was on a well-worn original Pacenti Pari-Moto. Those were known for their ultra-thin tread. Compass tires use a little more rubber under the center of the tread, which may help prevent those types of punctures.

  3. Peter Turskovitch says:

    “Punctures are less likely on gravel, because the tire pushes sharp objects into the (relatively soft) ground. On pavement, the hard road surface forces the object into the tire. That is why punctures from glass or nails are rare on gravel.”

    Is that true? I would have thought that there is just less glass and nails on gravel roads.

    • It’s probably a combination of both. In more than 15 years of riding on gravel, I’ve never had a puncture. Pinch flats, yes, but no punctures. No sidewall failures, either – touch wood – although I did cut through the first of three layers of my Rat Trap Pass in the 100 km Otaki Mountain Bike Race in Japan. I was running too high a pressure after having pinch-flatted twice and run out of tubes. Next time: tubeless!

      • Peter says:

        Hi Jan, thanks for the reply. What kind of gravel do you have in the cascades? I ask because I’ve noticed that the rock type makes a big difference where I ride (the Swiss Alps). Some roads are soft calcareous rock or “mudstone”, and I never have a problem there. In contrast, many roads are made of extremely sharp granite shards. On those roads I need to use ample sealant and inflate my tires as low as possible. Before sealant, I was simply unable to ride on these roads. I should note that I use compass tires exclusively.

        One horrible example is the gravel road bypassing the Lucomagno pass. It’s visible in the google map link below, crossing above the dam before veering to the south-west. The first time I tried this road I was on 42 mm compass tires with tubes, and I didn’t even make it 5 km. In that time I used both of my spare tubes and my whole patch kit (4 patches)… so 6 punctures. I assure you that these were not pinch flats and that I did not have a shard in my tires. I haven’t been back, but the experience led me to buy a whole new bike that could handle 2+ inch tires. I plan to return this spring on Rat Trap Pass tires set up tubeless and inflated to about 7 psi.
        Here’s the road https://www.google.ch/maps/@46.5674068,8.7935111,1762m/data=!3m1!1e3?hl=en

        Anyways, like most things, it’s not so simple as “less glass and nails = less flats on gravel”

      • Those do sound like extreme conditions, and it’s clear that high-performance tires, including our Compass tires, eventually reach a limit where they aren’t sturdy enough. That limit is much higher than many people realize, but it still exists.

        When I talk about “gravel”, I talk about “average” stuff, not the extremes that you seem to have encountered. I’ve ridden on gravel in the Cascades, in Oregon, in Japan, in France, in Ontario and in Colorado on our Compass tires. Oh, and Marin County, albeit not very far. I never had a puncture in all those places, which vary from “all kinds of rocks deposited by glaciers” (Cascades) to limestone (much of southern France). But of course, there always will be exceptions. I hope you have better luck with the Rat Trap Pass tires, but those roads may call for some sturdier tires, or even airless ones!

  4. larryatcycleitalia says:

    I agree – your tires work great for us on unpaved roads in all the bici d’epoca (as in l’Eroica) events we’ve enjoyed. “Gravel” anything is merely the newest-latest fad the industry wants to cash-in on!

  5. Dr J says:

    Compass tires are great not just because they roll well but also because they’re quite different than anything else on market.

    What I’m really waiting for though is a 54-58mm wide version of Switchback Hill (650B). Anything like it in development?

  6. Jan,

    I’m sorry, but you are very, very much mistaken about Automotive Rally tire choices for gravel. As someone who has been an avid follower of pro rally from the Group B era to the present, and someone who owns a rally car and a garage full of gravel rally tires, you are incorrect.

    Gravel rally tires have a distinct tread pattern designed to move gravel out away from the wheels, and from a performance perspective, it makes a significant difference. Bicycle tires are not the same, but your statement about pro rally teams using slick tarmac tires for gravel is incorrect, even in the Group B Audi Sport Quattro image of the Rally of Finland you are using. Audi Sport was a user of Michelin tires (everybody was), and used gravel tires for gravel, tarmac for tarmac, snow for snow.

    To view Michelin’s line of rally tires: http://www.michelinmotorsport.com/Tyres/Rally

    Sincerely,

    James Phillips

    • I’d love to learn more about rally cars. I followed car rallying closely only when I was a teenager, and I remember reading that the Audi Quattros had switched to slick tires on gravel, because they were faster than the gravel tires they’d been using before. That was pre-Group B, though, and slick tires were banned from rallying shortly thereafter.

      • The regulation in rallying is that the vehicles must be street legal (they transit public roads between special stages), which includes tires. In Germany, minimum tread depth for legal tires is 1.6mm, 2/32″ in the US.

        Regardless, the logic of racing slicks on gravel is absurd: the tire compounds for race tires are quite soft. Gravel rally tires will leave rubber behind on hard pack dirt; slicks are much more soft, gravel sticks to the tires like dirt to a gumball, rendering the tires useless for any kind of driving in anger.

        I agree that tread on bicycle tires has minimal impact on bicycle performance on gravel, but the situation is quite different when it is applied to motorsports tires that last less than 100 miles of performance use.

      • Perhaps that is why slick tires were outlawed, that they required the cars to be street-legal even during special stages? It’s peripheral to this discussion, but they really did use slicks on gravel on those early Audi Quattros. Not sure why and how they worked, but they won rallys…

  7. Dan says:

    You have mentioned several times that to avoid tire punctures to ride “light”. Can you explain that in more detail?

    • We’ve been thinking about what is going on, as it’s not easy to describe. You can see it when you watch top-level racers, especially in cyclocross. When there is a bump in the road, their bodies don’t move, because they allow the bike to move under them. On gravel, this isn’t just in the up-and-down direction, but also sideways. It requires a light touch on the handlebars and “hovering above the saddle”. It appears that allowing the bike to deflect as it hits rocks greatly reduces the risk of sidewall cuts.

  8. Guy says:

    I’ve had good results on gravel with 650b Babyshoe Pass, but have often wondered if I was missing anything by forgoing the fine knobs of so-called gravel tires. Thanks for this perspective. For truly muddy rides, I could still do with a 650b version of the Steilacoom – are there plans to introduce such a tire?

  9. Jeffrey A Guild says:

    Jan,
    I have a couple sets of your tires (rat trap pass and switchback hill), and I run both tubeless. Aside from being plush and fast, no pinch flats.
    Are you still running tubes and if so, why?

    • I’ve been experimenting tubeless. Not getting pinch flats is a big plus. Keeping track of the sealant inside is a bit of a hassle, though. When it dries out, the tires start leaking at the rim/tire interface.

      • Jeffrey A Guild says:

        It can be a little finicky and there’s a bit of a learning curve, but I’ll trade some time and prep back home in the garage for some additional speed and durability on the trail any day.
        This came to the top of mind when reading last quarter’s article on the Japanese MTB race you participated in. Tubeless next time?

      • For really rough gravel roads or mountain biking, it’s tubeless all the way! On the road, I am not yet convinced. As to speed, I am not aware of anybody who has tested inner tubes vs. tubeless. You get rid of the (thin) rubber tube, but you do have a liquid sloshing around in your tire. Which slows you down more?

      • I’ve never been able to perceive any sloshing around… Sounds like a great test for the BQ team (unless you want to donate a bunch of wheels and tires and I’ll do it for “free”)!
        As far as the sloshing goes, it would be interesting to see what is going on in there – my guess is that the centripetal force makes any sloshing negligible at relatively low rpm. Would be interesting to see a video from inside or through a clear tire.

      • I’ve been wondering what happens to the sealant. Since it actually seals the bead at all times – ride with the sealant dried out, and you soon start losing air, even without a puncture – I suspect at least some of it gets atomized into a fog from the rotations. The resistance probably isn’t great, but on the other hand, a butyl tube is extremely supple and takes almost no energy to deform, either.

      • Tom_Anhalt says:

        Jan, BicyleRollingResistance.com has done some work on the Crr effects of sealant:
        http://www.bicyclerollingresistance.com/specials/road-bike-tubeless-sealant

        More appropriate to your uses is probably the following test though, since it’s on wider tires and at lower pressures:
        http://www.bicyclerollingresistance.com/specials/tubeless-latex-butyl-tubes

        I’ve also tested tires set up with a tube (latex) and set up tubeless (same tire with sealant) and found no difference in Crr between the setups. Those have been traditional road tires of 23-25C width, and at higher pressures (100-120psi). That result of “no difference matches” the trend shown in that Crr vs. pressure chart in the second article I linked above. But, for lower pressures, it appears that running tubeless with sealant is lower Crr than even running latex tubes. That was a surprise to me.

        As far as the “sloshing” goes, I’m pretty certain that centripetal force with cause the liquid to basically be “flung” uniformly around the inside of the tread area of the tire…and so the only extra losses would be the shearing forces of the liquid in the contact patch deflection area…which must be quite tiny. This is the reason why sometimes when the sealant can’t quite seal a puncture while riding, it’s best to stop and put the hole at the bottom…while the sealant all then pools in that location.

        Lastly, for ANYONE running a tubeless setup with sealant, I HIGHLY recommend getting one of these kits for your repair bag. It’s JUST like an automotive tire plug, but downsized for the bicycle purpose. From experience, they work pretty well for larger punctures the sealant can’t handle by itself, and it’s significantly faster, and infinitely less messy than trying to break a tubeless tire bead in the field and swapping in a tube. Just an FYI: http://www.genuineinnovations.com/us/products/tools-accessories/tubeless-repair-kit.php

        BTW, I used that kit just last week on a Naches Pass tire that I’m running tubeless. Worked like a charm.

      • That is interesting. However, without a proper statistical analysis, it’s hard to know whether what is observed are real differences in performance or just noise in the data. Compared to our on-the-road testing, it seems that the steel drum greatly overestimates the importance of the tube. We tested heavy and light butyl tubes, and found no difference, while a (relatively thick) Michelin latex tube actually rolled slower. (We tested two sizes in two different tires.)

        Whatever it is, it appears that running the same tire tubeless and with a tube offers remarkably similar performance. It’s something we should test more carefully on a real road. There is a possibility that the tubeless setup reduces the suspension losses, which wouldn’t be measured on the steel drum.

      • Tom_Anhalt says:

        Hi Jan, I know we’ve talked about this before, but I think your previous testing has some un-modeled effects that might be skewing your data (and/or making it difficult to “see” certain differences). The more tightly controlled roller testing data is actually measuring the one tire property that affects losses in the tire. It would be possible to modify the roller testing setups to include a spring and damper between the wheel and the load mass, and use a “rough” surfaced roller. However, it’s probably more effective to use the smooth roller testing as it is, as a way to rank the tires for their low hysteresis losses. Then rely on field testing using a more controlled method than your coastdowns, such as the “Virtual Elevation” tests performed by myself and also by Silca (Josh Poertner) in order to understand at what inflation pressures the “suspension losses” in the system start becoming a large detriment to the forward motion.
        https://silca.cc/blogs/journal/part-4b-rolling-resistance-and-impedance

        It has been shown multiple times that below the “breakpoint” pressure of a particular setup, the rank order (and percent differences between them) of tires as determined in a smooth roller test match what is found in a well-controlled field test. This implies that the driving characteristic of the tires is the hysteresis losses in the casing and tread material, which is exactly what is measured on a smooth roller test. Here’s an example of one of those such correlations from Andy Coggan (he determined his on-road Crr using a regression analysis): http://www.trainingandracingwithapowermeter.com/2010/12/crr-roller-vs-field-test-results-part.html

        I guess what I’m saying is don’t make hasty conclusions about your own data when there are many examples out there showing something different 😉

      • It’s hard for me to believe that a butyl tube takes 1/4 as much energy to flex as a mountain bike tire. Just kneading them in my hand, the tire is pretty stiff, the tube has almost no resistance. For all these studies, I’d like to see some rigorous statistical analysis, just like we did for Bicycle Quarterly‘s tire tests. Also, the graphs on that web site look too smooth to be raw data. Our tire tests reported the raw data, so people could see for themselves what we actually measured. Without seeing that, it’s hard to even believe the hysteretic losses reported by these studies.

        It’s interesting that Josh finds a “breakpoint” when we did not. We tested many, many tires at many different pressures, once going from 60 to 200 psi, and there was no clear break-point anywhere. I’ll talk to Josh Poertner some more about this – we should be able to reconcile our studies somehow, considering we use the same methodology.

    • Tom_Anhalt says:

      Well, butyl is one of the most “lossy” of the rubber compounds used in tires. In fact, the rebound resilience is ~1/4 that of natural rubber (15% vs. 60%) in the range of temps a bicycle tire is typically used. As you well know, the main feature butyl is selected for use in common inner tubes is it’s low gas permeability. In other applications, butyl rubber is specifically used because of it’s large internal damping losses (i.e. in vibration isolators). Also, at lower pressures in a large tire such as a MTB tire, you can also start getting interface friction between the tube and the tire. That’s what is seen in the plot showing the 2 tubes and tubeless in the MTB tire at different pressures. Even the latex tube starts showing that additional frictional loss at the lower pressures, where it’s not pushed against the casing as tightly. So yes, that data is very believable.

      You may have missed it, but all the raw data points (run averages) for the BicycleRollingResistance plots are displayed in the table accompanying the article. I too show the actual power values (along with many other relevant properties measured at the same time) in my spreadsheet results.

      Statistical analysis is great, but as you well know, the commonly used tools (i.e. significance testing) can only tell you about random errors, and not systemic errors. It’s the latter that I think might be of some issue in your previous data, especially considering the details of the protocol. In the case of roller testing, the sources of random error are very small in the first place, so identifying and controlling (or measuring and modeling) the possible sources of systemic error is a much more valuable exercise in my experience.

      On the subject of your previous statistical analysis, what p-level did you choose, and why? Was it the “standard” p=.05? And if so, did you consider whether that was appropriate for the particular analysis and the effect sizes? I’m just curious really and I’m interested in the thought process.

      Yes, please discuss this all with Josh. As I understand it though, he used a form of “Regression Testing” (which looks at a plot of Power/Velocity vs. Velocity^2) to get an estimate of both CdA (line slope) AND Crr (y-intercept). The “Virtual Elevation” testing I do myself for field testing is a sort of special version of the same thing. Both are different than both the coast down testing you’ve done previously and (as I recall) the constant speed or constant power testing you’ve done more recently. The methodologies give more insight into possible systemic errors.

      Thanks for listening!

      • You are right, with steel drum tests, there is no need to show statistical significance. I was thinking in terms of real-world tests, where you are actually replicating what happens on a bike on the ride.

        As to our testing, we used two totally different methodologies (roll-down and constant speed with power meter) to rule out systemic errors. Our results were the same with both, which shows that there aren’t any systemic errors.

        The complete methods were published in the Bicycle Quarterly articles – if you are interested, we have a back issue 4-pack with all the tire test articles. However, a detailed article about the statistical analysis was in BQ 19.

        Mark Vande Kamp, who has a Ph.D. with a minor in statistics, did all the analyses. I’d have to look it up, too – it’s been more than 10 years since we did the first tests. It’s great that the “experts” finally agree that wider tires can roll as fast as narrow ones, and that higher pressures don’t roll faster…

      • I would love to see a BQ test on this. Suggest RTP, SBH, and BJP, all extra light, with and without tubes. From my own unscientific and subjective experience, I think Tom’s data is going to prove out in real world (but high rigor/scientific) BQ testing.
        My guess is that there are even bigger losses in cornering with tubes.

      • We are working on it. One issue is that the differences are likely to be quite small – the steel drum data suggests about 3 watt per wheel. This is on the lower end of what we can detect reliably in real-road testing.

      • As you have proven in the past, the drum test can over/under estimate real world testing. I put more stock in BQ tests.

      • Tom_Anhalt says:

        Aaah…only being able to detect differences in ~6W total in a field test is a bit on the high side for field testing. For a regression-type field test (similar in technique to Josh’s testing), Andy Coggan was able to discern differences approximately equivalent to ~1.5W total:
        http://www.trainingandracingwithapowermeter.com/2010/10/challenge-to-cycling-aerodynamicists.html

        For my own field testing (using the “Virtual Elevation” variation), I did a similar study based on Andy’s “Tom Compton” challenge, and had similar sensitivities: http://bikeblather.blogspot.com/2013/08/aero-field-testing-using-chung-method.html

        Now then, both of those tests linked above were concentrating on difference in aero drag, but could both be used for detecting differences in “on-road” rolling resistance as well, or as Josh termed it, “impedance”. In fact, that’s exactly how I created that first plot back in 2009 that Josh points to in his article that demonstrated the “breakpoint” pressure.

      • We can detect much smaller differences, but what we worry about is whether they are meaningful.

        What I’d like to see from all the experiments you mention is the basic scientific idea of repeatability. You do four runs with different equipment, and each time you get a different result. You conclude that the equipment differences caused those variations. But you don’t control whether other variables have changed – perhaps it’s getting warmer as you go from larger to smaller balls attached to your bike, and so your bike is rolling faster even without changing the aerodynamics of the bike itself.

        When we test tires, we test the same tires multiple times. We also test a reference tire at the beginning, in the middle and at the end of our test runs. That gives us a good estimate of how accurate our results are. If we didn’t do that, we could report much more precise measurements, but that precision would be meaningless. Based on all that, we estimate that at moderate speeds, differences of less than 3% are not measurable with a real rider.

        Even when we tested in the wind tunnel, we had up to 3% variability between runs with the same equipment. The wind tunnel people thought that was excellent, seems like Lance A., who used the same wind tunnel, was moving around on his bike more.

        At some point, you also have to wonder whether it still matters. Considering that raising your stem by 20 mm can increase your aerodynamic drag by 5%, perhaps it’s pointless to worry about 1-2% differences? Back to the original question, if tubeless tires and those with tubes are within 3% of each other, then I wouldn’t consider either option superior based on performance alone.

  10. ST. says:

    yes, the only downside of these beautiful rolling tires are the weak sidewalls. experienced it myself.

    • Strong sidewalls means slow rolling – there is no way around it. Other companies make tires with a lot of “protection” – Panaracer’s Pari-Moto and Gravel King tires are good examples. (I just wish their center tread was a bit thicker, so they’d last as long as our tires.)

      Compass tires are designed to be the fastest and most comfortable. Most riders have no problems with them, but it all depends on how and where you ride.

      • ST. says:

        I use your tires, they are great. just when your out in for example Romania or Georgia (Caucasus) for 4 weeks, only off road, thats a bit risky. 2015 in Romania I had a clean sidewall cut. 😉

      • I think if you venture that far off the beaten path, you should carry a spare tire, no matter what tire model you run. But I also agree that Compass tires are high-performance tires. There are conditions that are so rough that high-performance tires may not work…

      • ST. says:

        always carry a spare one when touring… 😉

  11. julianactive says:

    Tubeless is a commitment to learn but mountain bikers have embraced it. Fewer flats, the ability to run lower pressures and reportedly better rolling resistance. I ride my mountain bike in the desert of southern California and there is no way you can get through most rides without a flat if you were running tubes. Then with goat head season running tubeless is a no brainer.
    Every few months we break the bead on one side, take out the dried “Stans bugger” and then add some more.
    I have been running 6 of your Compass tires tubeless and there is no way I would go back to tubes.
    I ride your 44C tires on gravel and for the most part they work pretty well but I did crash trying to come out of a rain rut that my 3 inch tire mountain bike would have laughed at! I would certainly like and buy a tire in 700C that was at least as wide as your rat trap pass tire. I think there would be a nice sized market for a tire like that since you could put it on any 29er mountain bike. It is funny when I ride my 44c Compass Snoqualmie pass tires and they look too narrow!

  12. Conrad says:

    I would take it one step further and say that knobs are really overrated for mountain biking, too. If it is muddy enough to make the knobs truly worthwhile, you probably shouldn’t be on the trails. With the rat trap pass tires, I don’t dread riding to the trailhead. Once I am on the trails, the performance of the rat trap pass tires are at least as good as my old knobbies.

  13. I’ve got a set of 700 c Snoqualmie Pass ‘extra light’ casing tires mounted on my ‘gravel’ bike. Compass says that the tires are ‘tubeless ready’ – yet I found them impossible to mount on a WTB rim that I was previously able to mount a tubeless tire on. Has anyone else had issues with tubeless mounting of this particular tire. I’ve got an air compressor and tons of sealant… any ideas ?

    I’m not sure using minimal tread tires in ORV or rally cars is a good analogy for bike tires – the mass per contact patch surface area is higher in ORV/auto case, so more displacement loose material and better cornering with less skidding. On a bike, there is less displacement of material and traction relies more on tread’s engagement with surface material under tread.

    Thoughts ?

    • WTB rims vary a lot in their diameter. We’ve had some that were great, and some that were clearly undersize and very difficult to mount tires on. With supple tires, the interface is a bit more crucial, as the tire doesn’t hold its shape on its own. That said, with a little massaging of the tire (pull the bead outward so it sits on the shelf as much as possible before you start inflating the tire), we’ve been able to mount tires even on the smallest WTB rims.

      It appears that the tolerances vary from batch to batch, so you either get two good rims or two not-so-good ones. Compass sells HED rims, because we’ve found their quality to be more consistent.

    • Conrad says:

      The wheel fanatyk wrote some great things about this. There is very little variance in bead diameter and rim diameter for any given model of tire or rim. Between models, there is a lot of variance, such that some tire/rim combos flat out don’t work. I prefer to use an asymmetric rim for rear wheels. Now that velocity discontinued the Synergy, my only option is the A23, which is a tubeless compatible rim and generally a pain to mount Compass tires on. If I lived in goat head country I might be more excited about tubeless. My personal observation in cyclocross and gravel races around here is that far more mechanicals are due to burping tubeless tires, compared to pinch or puncture flats. Changing a tube on a tubeless rim usually involves 10 or 15 minutes, some snapped tire levers, bruised knuckles and plenty of cursing. I can change a tube on a normal rim in less than 5 minutes.

      • On good tubeless-ready rims, it’s no harder to install tires than on classic rims, but the technique is a bit different.

        First thing, you must use a tubeless rim tape (even if you use tubes). Cloth tape is too thick and to rough to allow the tire bead to slide onto the shelf where it needs to sit. I’m surprised that there are still experienced mechanics and wheelbuilders who use cloth tape with tubeless-ready rims. Don’t!

        Second, you need to make sure the tire bead is in the well all the way around. Push it to the center everywhere. If it’s hung up on the shelf anywhere, you will get the scenario you describe. And with supple tires, it’s more likely to be hung up in just one place, because the sidewall is so flexible. So if in doubt, check again!

        Then it’s easy to mount the tires. Since most modern rims are wider (which allows for a deeper well in the center), I usually can take off and install the tires without any tools, and without needing exceptional hand strength. Having to equip every Bicycle Quarterly test bike with our reference tires – otherwise, we’d be testing tires, not bikes – I’ve got practice now, including with the Synergy A23s you use. The only ones that have needed tire levers are the Bontrager carbon rims on our Specialized Diverge long-term tester and a set of Reynolds carbon rims. Enve carbon rims mounted like a charm by comparison.

        It’s not very difficult – it’s all about finessing the bead.

      • Conrad says:

        What kind of tape do you use? I am not using cotton, but the strips I have tried don’t stay in place very well.

      • Stan’s tape comes in big rolls, and it works well.

  14. david says:

    I am in the middle here in the South East. Our “gravel” is most often rock, or mud or a dry almost talc…all depends on location and weather. In the summer the roads have a dry dust that is almost like talc…. horrible to ride on. I use the Soma CAZADERO then with good result; the Baby Shoe Pass cant get any traction when it is steep. When the roads are more “normal” the Baby Shoe Pass is perfect but then when things really wet it is back to the CAZADERO.

    I have chased the perfect tire pressure on the baby shoes a LOT. Too little and I pinch, too much and I bounce! I love the ultralight Baby Shoe but it can be an expensive learning curve for sure.

    The CAZADERO is fine for what it is but I will be getting the Steilacoom very soon.

    • Perhaps fine talcum powder is the one place where the Cazadero’s tread with lots of small, closely spaced knobs works. When we tested them in typical Seattle conditions, we found that they clogged up immediately in mud. On the road, the small knobs suddenly folded over in corners, causing the bike to slide unpredictably. In fact, what we learned from the Cazaderos helped us tremendously when designing our Steilacoom knobbies – wider knob spacing for mud clearance, and larger knobs so they don’t fold over on pavement.

      • David says:

        Yep, I have experienced the “insta clog” more than once. There seems to be a very small widow where they excell but that is it. I made the mistake of trying to ride in town on them and realized that, at speed, they are downright dangerous.

        I am far (very far) from being or riding “light” but I try to and have seen a significant difference in saving the sidewalls. Years ago I would bomb around on MTBs and monster tires and it took a bit to get out of that habit and really ride as if I am on a much more fragile bike and try to pick the line and float….

        (Sure sounds good….in reality I am sure it is more like the Michelin man on a suicide mission but the plan is sound)

  15. I love your tires Jan. I ran the BSP ELs last year in the 4300 mile Trans-Am bike race and they performed wonderfully. I suspect more and more racers will start using wider tires as they continue to gain acceptance. Many more production bikes can accommodate them now.

    This year I will be taking on the Tour Divide. Most of the route looks like it would be manageable on non-treaded tires but it is a long race with plenty of chance for very long stretches of mud.

    Jan – if you were lining up for the TD what tires would you chose?

    • I’ve been thinking about the Tour Divide. It’s a fascinating race. Much of it is on gravel roads. Even on mud, if it’s not clay-rich (which you only find in valleys), tread isn’t necessary. (I had plenty of springs that made the trail muddy in the Otaki Mountain Bike Race, and never spun my wheels.) So I’d go with the Rat Trap Pass or Switchback Hill Extralights, if you want to win. You’ll gain much more time on the non-muddy parts than you loose in the places where a knobbier or sturdier tire would provide an advantage.

    • WillK says:

      I think non-treaded tires are ideal for (parts of) the Great Divide route. June 2016 I rode the Canada and Montana portions on 700×38 Barlow Pass standards (with tubes and Velocity Dyad rims). Compass 29×2.0, tubeless, with wide rims, would be ideal. I pinch flatted a couple times on fast chunky gravel roads. No punctures. I was riding a cross bike, but I kept thinking how my 90’s rigid MTB with RTP tires would have been a pleasure.

  16. Simon Norris says:

    If you were to offer tires with the volume and outer knobs of the Steilacoom but with a file tread or road tread on the centre, I’d be eager to try them for my riding. Something like the Schwalbe Sammy Slick. I haven’t tried the Steliacooms – they would be far too knobby as my cross bike sees mostly gravel and pavement… but my excellent Bon Jons slide out pretty quick when cornering on dirt/mud.

    • Try the Steilacooms on pavement. They roll remarkably well. I just did a long road ride on them yesterday, and was surprised how well they corner, and how easy it was to keep up with the other riders. The knobs are staggered, so that the transition from one knob to the next is smooth, rather than falling off one knob and having to climb up the next. And the knobs are big enough not to fold under hard cornering. Subjectively, the Steilacooms roll and corner 90% as well as our “road” tires, which is pretty darn good…

  17. Harry says:

    I love my Compass tyres (I have SBHs and RTPs), but to say that knobs make NO difference on gravel is a bit much. I live in the country, so I ride all kinds of surfaces all the time (Grass, dirt, hardpack, mud, blue metal, pea gravel, tarmac, blah blah), and generally the tyres are fine, nay, excellent. They do start to slide earlier than knobbies on most gravel roads, probably more where the gravel is thin, and knobs would cut through the gravel and bite in hardpack underneath. When gravel gets wet they can be a bit more treacherous too (perhaps here knobs can find more purchase as the gravel starts to bind together, whereas the slicks keep slidin). Anyway this in no way diminishes my love for them, there must be compromises, but making blanket generalisations like you did is just asking for robust discussion 😉

    • I can see that under some of the conditions you mention, knobs could help. It all probably depends on the gravel. Note that dry-weather cyclocross tires don’t have knobs, either. It’s only the “Super Mud” ones that feature knobs. These Clement Grifos (from the old Clement, no relation to the more recent company that uses the name) were the standard “dry-weather” cross tire of the 1980s:

      Classic Clement Grifo cross tire

  18. Ray Varella says:

    I notice that Compass offers a “Freeride” tube for the RTP sized tires.
    Any plans to offer that tube for 650b or 700c?

  19. I’ve used your tires since they came out. Last year I used them on a gravel ride and got 6 flats in a 100K ride. I can only attribute it to the tires. I am reluctant to go on gravel roads with those tires again.

    • Sorry to hear about your bad luck with flats. 6 flats in 100 km would be a record for me, too. Which tire model did you ride, and what caused the flats? I agree, it seems that the tires were not well-suited for the conditions. Often, going to wider tires helps a lot, but of course, we all ride the bikes we have, not the ones we wish we had…

  20. Jacob Musha says:

    The Rat Trap Pass is probably my favorite tire ever but I have one nit to pick. Will you consider changing the name/description from “26 x 2.3” to “26 x 2.1″ since that is the actual width? If I remember correctly the tire was intended to be a 2.3″ but since mold sizes can be unpredictable, it ended up at 2.1”. In the specifications it is correctly called out as 53-54mm actual width, but it might be confusing to someone trying to decide if it will fit their bike when they see 2.3″ (which converts to 58mm).

    • I am glad you enjoy the tires so much, and that your only complaint is related to the writing on the sidewall. There are a number of reasons why it was called a 2.3″ – but changing the tire molds (the size is molded onto the sidewall) is difficult. If you use a very, very wide rim and mount the tire tubeless, the tire actually will be close to 58 mm wide.

    • Alex says:

      This bothers me a bit too: not the nomenclature (but perhaps drop the outdated & inaccurate imperial/french measurements. . .), but the fact that the prototype came in below targeted width (AFAIK the only one of the Compass tires to do so: you mentioned that in your ‘intro’ blog to the tire, Jan). I use 55-559 Continental Race King *RaceSport* (the last word being extremely important: *RaceSport* is Conti’s extralight line), & it’s a true 55 mm & builds very high (is taller vertically, and thus has quite a volume).

      Leaving out wet/dry performance for now: in highly unscientific but long tests here in Brandenburg (as in concerto), I felt the Race King *RaceSport* was better than the RatTrapPass on everything but ‘forest highways’ (homogenous dirt/packed sand trails analogous to gravel roads, which we don’t really have here). Most of the terrain is flat, but extremely heterogeneous (non-smooth/inconsistent), varying every few minutes: roots/sand/mud/bumpy canal banks full of tall grass & animal holes, & all combinations of the above.

      I think the Race King *RaceSport* was better for two reasons: considerably greater volume (a real shame RTP is below 55!), and an even more important factor: the running surface of the Conti tire has small nobs like an overblown cross tire, but between the nobs it’s considerably thinner than the RTP, thus allowing more flexibility on heterogeneous surfaces. This last aspect deserves considerable study, I feel, & Jan, it’s perhaps here where a study of top notch minimal-profile MTB tires would pay off. There are very few out there!

      • The story of the width is a bit more complicated. The tire was based on a 2.3″ mtb tire originally. The casing is the same size, but since we don’t have shoulder knobs (and a thinner casing), the final tire is a bit narrower. Panaracer made Compass tires, and somebody put the 2.3″ back onto the mold drawing after we approved it. We advertise the tire as 54 mm wide, which it is, so I don’t think anybody will be disappointed.

        The idea that small knobs with almost no tread in between can flex more is interesting. I’d be concerned a bit about punctures in those “ultra-thin tread” spots, though.

      • This is the Thunder Burt recipe too. Although TBs seem to roll faster than RTPs ime, I have given up on TBs because I get so many punctures thru the tread just riding on normal dirt roads. It seems any type of rock will slice right thru the TBs, it’s always in between the micro knobs where the casing feels super thin. Sealant helps, but I’ve had to patch the tire every time (after I get home) to get it to stop leaking. I ride the same dirt roads with RTPs and have not yet had a puncture from rocks.

      • When we designed the Compass tires, we made the decision to add a little rubber in the center of the tread. The weight penalty is small, the rolling resistance penalty even smaller, but you get about 2x the wear life and much better puncture protection. For us, it was a trade-off worth making. Even in racing, you must arrive first in order to win.

  21. Thomas Sommer says:

    Hi Jan,

    this is the tire size of my current bike: 40-622 (28 x 1,50)

    so I assume the best fit would be your Compass 700C x 38 Barlow Pass, right?

    What is the difference between them and lets say the ‘Bon Jon Pass’ or ‘Stampede Pass’ – is it only the size?

    Where can I get Compass tires here in Germany?

    Thank you

  22. marciero says:

    Perhaps a little off topic, but I had read, perhaps here, that 650b 42 will be about the same wheel + tire diameter as 26″ rim with the 52 Rat Trap Pass. This sounds about right-if you take the difference in bead seat dia and divide by 2 you get about 12.5mm smaller radius. Assuming a round profile for the tires, the RTP at 52 would be about one cm taller which would make total radius only slightly smaller (though perhaps the lower pressure will make them sit a little lower.) So in consideration of chainstay clearances, with the fattest part of the tire is at about half the tire height less in radius. So rough calculation assuming round profile tires would put the fat part of the RTP about 7.5 mm smaller in radius than 42 650b. How does this play out in practice? Am trying to figure out where/how to measure for clearances.

    • I measured a 42-584 mm Babyshoe Pass and a 54-559 mm Rat Trap Pass. They were within 1 mm in diameter. The widest part of the tire is about half the diameter, so at 21 mm from the outer circumference for the 650B Babyshoe and at 27 mm for the 26″ Rat Trap. Difference is about 6 mm toward the rear on the chainstays. Plus or minus 2 mm, I would guess, as so much depends on your rims and other factors.

  23. julianactive says:

    YouTube is your friend for a lot of things. For tubeless I use two layers of gorilla tape and spray on a generous mixture of soap and water between the sidewall and the rims. I take out the removable core from the presta valve and then use a shraeder connector on my compressor hose to introduce a huge rush of air into the tire. Some people use an air nozzle. I make sure my compressor is adjusted for high pressure since the more air you can get into the tire the better. Sometimes with stubborn situations you might want to air it up with a tube to seat the gorilla tape to the rim and to stretch out the tire to the rim.
    I don’t put in any sealant until I can get the tire to seat tubeless since I have had too many messy encounters! You can either crack one bead to put in the sealant or I just put it in through the presta valve with the core removed. You can use an injector or a tube.

    • I don’t have a compressor, so for most of the tubeless tires I’ve set up, I used just a floor pump. (For the last BQ tire test, we used the compressor at Brandford Bikes, who also lent us the 14 wheels we needed.) The only one that refused, even with a compressor, was a set of WTB 650B rims… They were significantly smaller than all the others. It seems that their size varies from batch to batch. Stiff tires tend to work even on those rims, since they keep their round shape even without air.

      I also introduce the sealant after the tire is seated, through the valve with the core removed. That way, if I have problems, I only have a dry tire to deal with, not sealant spilling out…

  24. Jim says:

    I had a hard time getting Gorilla tape to seat my tires but as soon as I used 2 layers of Stans tape they popped right on. That was with Baby Shoe’s mounted tubeless and have been running them for almost a year with the only issues I’ve had is when the sealant gets low they lose air.

    • I’ve been running Rat Traps, Switchback Hills and Steilacooms tubeless, and my experience matches yours: When the sealant gets low, the tires start to move against the rim, and that breaks the seal. Then you start losing air quickly… without any punctures. It’s a sign that it’s time to top up the sealant…

      • STS says:

        Jan,

        I’m sorry (really!), but I would beg to differ again. If an active sealant is necessary to keep the connection between rim and tire bead airtight then that’s a sign for a less than good fit of the two. A tire with a properly designed tubeless bead on a rim that is meant to be ridden tubeless will not leak or burb air their even without any sealant at all.
        And that’s not (only) theory but well-experienced real world practice either with high pressures on narrow road bike tires as well as on low pressure gravel and mountain bike wheels.

      • I think a big difference lies in the supple sidewalls. The tire flexes completely differently, and so it’s much easier to loosen the bead in just one place with Compass tires than it is with the tires you’ve experienced. At the other end of the spectrum, you have a car tire, where you don’t run any sealant, yet it doesn’t lose air even in months… but the sidewalls are incredibly stiff.

      • STS says:

        The more supple the sidewalls the better also for the bead retention because a very supple sidewall can only transfer the tensile forces created by the pressure onto the bead which every sidewall does no matter how stiff it is. It’s in fact a function of how stiff (= tensile stiffness = E-modulus) the bead core material is and how tight the bead sits on its shelf close to the rim’s sidewall. If it literally “pops” into place during the installation of the tire and then ideally finds an interface designed to keep it in place with the aid of a hump there will be so much friction that it will not move a jota even under the highest braking loads a bicycle can generate.
        Modern high performance tubeless bicycle tires like those made by Hutchinson or Schwalbe’s Pro ONE and G-ONE of which I have cut up some use either carbon fiber (and not the relatively stretchy Aramid fibers) or a fiber called Zylon (as stiff as most carbon fibers but easier to handle), both with very high E-modulus to make sure they don’t stretch. In fact it’s only the rubber surrounding the bead core that “gives” and thus makes it possible that the bead jumps over the hump during the installation with that reassuringly loud “pop”.
        Your all to understandable preference for wide and very wide tires creates a lot of pull onto the bead just because of the big skin surface of the tire. Even though the pressure is low. And that pull stretches, lengthens the bead core just enough so that the interface of bead and rim leaks some air which is prevented by the sealant as long as it’s active.
        For perfect tubeless performance you should therefore discuss with Panaracer whether they can use a different bead material with a higher modulus. But probably you have already had that discussion as they are also offering high pressure road tubeless tires in the meantime.

      • The bead used for our tubeless-ready tires already has the highest modulus available. One issue is that most rims our customers use don’t have the little ridge to keep the bead in place, just a flat shelf. That makes tire installation and removal easier, but you need the sealant. As to a stiffer sidewall, like that used by Schwalbe and Hutchinson, being better or worse for bead retention, our on-the-road experience indicates that the supple tires can move more.

        We have the same issue when installing or removing a tire on a tubeless-ready rim. A stiff tire will pop off the shelf inside the rim, and then the entire bead will be in the well. A supple tires will pop off in one or more places, but the bead still can be hung up on the shelf in other places. It’s not a big deal, but it requires extra care when installing and removing tires.

  25. Dr. Bob says:

    Those looking for a larger 29’er should check out Schwalbe’s 29×2.35 Big One. Lowest drum rolling resistance of any tire tested. Lighter and faster than Super Moto. I run them on road and hard pack and they have been as good as Compass tires. Run liteskin with tube and skinwall tubeless. My Jones Ti Spaceframe is road bike fast with major stability and comfort. I weigh 260 lbs. and run 40 psi. A high tech ballooner that is great fun.

  26. Sam Krueger says:

    I’m a big fan of your blog and Compass tires. But I’m confused by my real world experience here: if i ride my “road” bike with slick tires on a California dirt trail (we don’t have any gravel here that I’ve ever seen), even one that is totally dry and packed, I have so little traction I can barely make it up a hill or make a turn. I have to stand up and pedal super carefully while weighting the rear wheel on an uphill, or again be super careful on turns. I’m running a 32 mm compass on front, 28mm on back (maximum widths I can fit).
    What’s going on? Is there a point where the smooth tires get so wide that they grip completely differently? Obviously mountain bike tires have tread, and it seems like it’s needed. Is this all in my head and I actually could have more traction? It sure doesn’t seem like it.
    Befuddled in Berkeley…

    • Lower pressure and wider tires definitively give you more traction. Beyond that, on some surfaces, there simply isn’t much traction. Sand is a great example. Even knobs will slide there. However, if you feel that knobs could cut through to a harder surface, why not try our Steilacoom knobbies. They roll very well on pavement, and they offer excellent traction on mud.

    • HaloTupolev says:

      >”even one that is totally dry and packed”

      It seems like *total* dryness can be a bad thing on some hardpack. In some cases, a slightly-moisturized surface will be firm, but a totally-dry surface will be dusty and loose. Without water binding them, the particles will slip if you subject them to high pressure. Wide tires, with a bigger contact patch, spread the force over a larger area; the tire is contacting more stuff, and the underlying surface is less eager to give way.

      In my experience, as far as Seattle-region examples, Lake Cavanaugh Road off of highway 530 is a good example. There’s a particularly steep spot leading up to a switchback complete with a gorgeous view of the valley; narrow tires simply won’t propel the bike forward if the road is bone dry, but they seem to be sort of manageable if there’s been recent rainfall.

  27. John Smith says:

    My issue with Compass tyres is that as soon as it gets even remotely damp mud or leaves it is almost completely unrideable at any significant speed due to a lack of traction. Dry conditions are perfectly fine. I wish Compass made an Allroad tyre with a little bit of tread on it like the SOMA C-Line tyres.

    I currently use the SOMA C-Line tyres and the little bit of tread that they do have actually allows you to ride when the conditions get damp with wet mud/leaves without falling over.

    • Wet leaves can be treacherous, and mud is, well, mud. However, I’d be surprised if the tread of the Soma C-Line, which looks identical to the Panaracer Pasela, will do much there. It’s just a few sipes cut into what essentially is a slick tire. For mud, you need knobbies!

  28. Will says:

    Interesting discussion. I’ve been tempted to try a Compass/Gravel King/etc. My regular gravel tire is a simple Ritchey SpeedMax Pro on Stan’s rims – they’re light but the 32mm still comes out to about 34-35mm with plenty of volume to play with, and I find the file tread in the middle gives a decent amount of durable centerline tread and flat protection while keeping them fast enough for paved sections. The side knobs I could give or take on easier gravel and paved cornering but my feeling is they help a lot with sidewall protection on sharper surfaces, especially with the tire profile they take on with wider rims. I’ve only flatted once ever on this set up (pinch flat from unsighted downhill pothole) in thousands of miles of gravel.

    I’ve also ridden gravel on tubeless CX tires, and cheap mostly-slick urban tires – I felt that the CX tires’ knobs are generally wasted on gravel and the softer compounds a little too vulnerable to punctures (through the tread). The stiffer, slicker tires were obviously less comfortable but rode fine otherwise which is why I’m tempted to try a suppler version, run tubeless. My concern would be sidewalls.

    The recent CX Worlds was interesting for tire nerds too – seems like all those low-pressure supple tubulars did not fare so well with sharp rocks and debris.

    • Sidewall protection is important. We design all our Compass tires that no sidewall is exposed when you look at the tire from directly above (or below, in the case of rocks poking out of the road surface). I am surprised that many other tires either wrap the tread around the tire further than necessary (making them less supple) or exposing the casing to direct hits (making them vulnerable).

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