One thing that most of the testing I’ve seen overlooks is that suspension tends to water down the advantage of bigger wheels. Not remove, but make smaller than they would be on rigid. I am curious how much difference there is when comparing 2 120mm bikes. Probably won’t know for a while
What’s the reference for this? I’ve only seen one instance of this and it was a somewhat niche scenario.
Logically it makes sense - where bumps / hits need to be 100% absorbed by the tire on a fully rigid bike, with a suspension, some of those bumps can be absorbed by the suspension itself.
I’ve seen this mentioned where people have tested 2.4 vs 2.2 (not sure how scientifically though) - choosing the 2.2 on a FS vs 2.4 on a hardtail for this reason. (Keegan at Leadville?)
So, I can see the 32” being faster in some scenarios, slower in others. Same reason you see testing differences from pavement, class 1, 2, 3, 4, etc….
This absolutely jives with my experience. I’ve done a good bit of gravel racing on my FS XC MTB against rigid gravel bikes and there is some terrain where full suspension is dramatically faster. Not just technical stuff where you’d expect suspension to shine, but that super heavy/chunky gravel, rutted roads, etc.. These are sections where it’s bumpy enough that Flight attendant is going into pedal mode or sometimes fully opening the suspension it’s so rough. It becomes obvious in a group where there are folks running the same tires on gravel bikes while struggling to hold my wheel when I’m on a MTB. And then on the smoother sections, that dynamic goes completely away. If gravel races had more sections like those, everyone would run suspension.
And I think there was a study by someone comparing big gravel tires vs. smaller gravel tires w/ front suspension and I believe the smaller tires came out on top when combined with suspension. I can’t recall the details or whether it was just a “bro science” test or somewhat valid, so take that for what it’s worth.
This article perhaps? Think MTB tyres are fastest on gravel? Think again.
This is something that warrants further investigation. Unfortunately the EC test was not performed well, as it was specifically limited by sponsor obligations. After reading all the critique; the article weighs in more as click-bait than relevant experimentation.
Joh Poertner and Tom Anhalt raised several points in the comments, probably the most succinct summary of issues here:
I would suggest a change to the title of the article as in fact, no actual fast MTB tires were tested in this test.. I get that it’s a great title for getting clicks, but essentially this was two days of testing that showed the lowest casing loss tire was fastest when unsuspended and the second lowest casing loss tire was then fastest when paired with suspension allowing it to be run at higher pressure, which likely was also predicted by the casing loss data. Our data show a 12% reduction in Crr for a 45mm Cinturato on a smooth drum when increasing pressure from 20 to 25psi, which more than offsets the ~7% loss in efficiency that tire has to the 40mm tire when both are run at pressures giving them the same effective spring rate.. so to echo Tom’s point below, the system is still likely being dominated by casing losses.
From Marc Graveline, the consultant/coach who performed the testing, etc.
Not sure what you mean. We tested same tires with and without suspension fork. We even tested with suspnsion fork locked. We tested the best performing tire with suspension without the suspension and vice versa. BTW, the goal of this excercise was to optimize one athlete given the boundaries she can race with, ie a preset group of sponsors.
After a number of the big bike brands were slow to adopt 29ers such as Trek and Giant, it’s sounding like behind the scenes this time they are all in on 32”. It makes sense as sales of bikes have been down and this is going to be a huge opportunity to put the marketing team into “overdrive” to hype the product. I suspect we are going to see the shift sooner rather than later.
Thanks, that’s the one I was thinking of. And yeah, it looks suspect.
But this is one of those things that I’ve seen first hand enough that I know to be true. I don’t expect anyone else to take my word for it, but there are some situations that the difference is really dramatic. Not a marginal thing, I’d bet it’s 30-50 watts on some road conditions. Enough to ride people off your wheel when they are pushing similar watts running similar tires. The challenge is the same as when debating any equipment choice for gravel racing. Courses are often dynamic and an advantage in one spot can be a disadvantage in others. A couple small sections where suspension is a cheat aren’t going to help you win a race unless it’s a section leading into the finish and you haven’t gotten dropped yet.
Let’s not go too crazy. His teammate was on 29” and I assume they ride together….
Of course 32” wheels are faster. That’s why motorcycles have used that size forever.
Joe
Is there another tire we want to focus on for the BRR votes?
I see the Pirelli Scorpion XC M Lite 29x2.4 is listed now so perhaps that may be a good option?
If you bother to watch the Cape Epic Stage where the 32 inch wheel “won”, you will note that he was towed to the line by his teammate who was riding a 29er. In fact, the teammate with the 29er did all the work with the 32 guy struggling to hold his wheel. I wouldn’t be so fast to jump on the 32 wheel bandwagon.
You are really taking a not very serious comment about a March race result way too seriously.
Sure, but he wouldn’t have been able to hold his wheel were it not for the 32’ers.
There is the EC test, but LMN over on MTBR (I think he is Katherine pendrel’s husband) mentioned having seen testing on that.
It also makes sense from a thought experiment. One of the benefits of a 32 is that it rolls over obstacles better, but if the wheel can move up over the same obstacles/undulations, that reduces the disadvantage smaller wheels have.
It also aligns with my experience.
When I raced a 29 hardtail in college, some of the other racers had 26 fs bikes. When it came to pedaling over small (1-2 inch) embedded rocks and roots, those bikes still were much faster. There was one short track race that was just bumpy for the 80% of its length, and I got lapped by one of those riders who did not beat me in a race the rest of the year, before and after.
That course was abnormal, but it highlights the point that suspension and wheel size are solving different things, and so having suspension allows the demands on the tire/wheel to be different. While there’s no suspension out there I won’t be looking into 32s. I am curious to see people test them though.
I did a janky cyclocross race last year that was horrible bumpy, some dude on an FS MTB just rode away from everyone. When it is that bumpy you just cannot stay on the power.
IMO the early days of 29ers were bad, very bad. Frame makers took a while to get the geometry right and in fact I am not sure all makers have taken full advantage of what 29 wheels have to offer. Dan Empfield has written about that, and how much impact it makes on how the bike responds to a bump on the road by simply changing tire width. Because of geometry change and not tire volume effect. And that is for road bikes and maybe champagne gravel. I can only imagine the bumpier it gets the more relevant proper geometry is. Looking forward to what the engineers come up with and how the adapted bikes perform.
Maybe I’ll take my 97-98 Trek HT for a spin. Just to remember how terrible that geometry is.
Any chance you’ve got a fatbike and can compare difficulty to seat the Scorpions to fat tires? I’ve had several fat tires that left me swearing. And a couple gravel tires too.
I can’t compare to fat bike tires but every Pirelli tires I have installed (P Zero for the road and Scorpion for MTB) have been harder to seat than other brands like Continental, Schwalbe or Specialized. Once they are installed though they keep their air extremely well.
Are people riding the Rock XC without inserts ? I read a statement by Schwalbe saying that the tire was designed with those solid strips on the shoulders to reduce the need for inserts. On paper, it sounds like an interesting idea, even if those don’t make for the cushioning effect of an insert to protect the rim, working rather as snake bite protectors I assume. Not using an insert offsets the higher weight of the Ricks compared to other tires