Sooooo, I think I notice an interesting tangent here:
Pavement rolling resistance of gravel and mtb tires … at the psi people are racing them for mixed surface events.
Right?
For me this would just be whatever pressure I’d run them on gravel anyway, so around 19-20 for a 2.2 and mid 20s for a 45.
Just wanna make sure I’m reading some of these comments correctly before I mess with this any further. Thx.
You can do your own testing reasonably easily.
Then decide what trade offs are best to get the fastest overall time and not get dropped on any deciding moments in the race.
Just going with a single tire width regardless of course is not the fastest option.
That’s about right for me at @77kg’s, maybe mid/upper 20’s for the 45’s.
What part don’t you agree with? Are you disputing the fact that a mtb tire is slower on pavement or disagreeing that it matters?
Basically the same for me. 2.1/2 is 19-20ish. 45 is 23-25ish. Seems to work well enough from my experience and testing.
Nice. Ok… so this is an area with VERY minimal testing from anyone.
I’ll see what shakes out. New test round starting today.
Both.
Although I’m concerned with the fastest MTB tires versus the average gravel tire, as well as the fastest gravel tires. There’s more overlap with the latter but even then I think suspension losses, hysteresis advantage, and general handling favor the MTB tires.
Race King/Dubnital, Thunder Burt vs. Caracal Race, RS Pro, EL Rene Herse, and Pathfinder, Thundero, Terra Speed etc.
People isolate the pavement sections without evaluating where they are in the whole. Many times the hypothetical success one would have had on pavement doesn’t exist because the narrower tires would have failed the selection earlier. I think suspension losses and handling have a much harsher and final selection criteria than aerodynamics and possible unrecognized hysteresis losses.
Regarding bigger tires, I am looking forward to the upcoming BRR results of the Schwalbe G-One Speed Pro 60. I predict they won’t be as fast as the Caracal Race on the drum but would probably be faster on Cat 2 or rougher, if not also on Cat 1. Seems like a large volume low profile tire with a good casing could help mitigate pavement losses while also maintaining some gravel gains.
I would like to counter this by adding in puncture protection.
The fastest MTB tyres have poor puncture protection. I’m pretty tired of seeing race ending (or result defining) punctures from thunder burts, the latest at The Gralloch where only 1 guy running them that I know survived puncture free for the race.
Rolling resistance is of course important, but it has been weighted far too highly recently and anecdotally the number of punctures is increasing due to the increase in RR focus.
I agree many racers are very slow to adapt, versus the sorts of people that spend time here - however it can also go the other way where the bigger picture is ignored because individuals go down a specific rabbit hole and end up making a poor decision.
Prime example - I qualified for worlds at The Gralloch running 48mm (50 measured) Thundero HDs. They are incredibly reliable for the sharp flint found on this course, and there were punctures and abandons all around me. They allowed me to descend at full speed, shift position across the flint where necessary, and didn’t seem to give up too much on the very limited tarmac sections.
I think you’d struggle to find a more appropriate tyre for the course - either because it is too susceptible to punctures, or overkill for the relatively consistent gravel type (loose, but not rocky).
Fastest measured is only fastest in reality for a solo time trial without any mechanical incidents. Not to mention, resistance values have completely different meaning when drafting (say the difference between 220-230w, which has practically no physiological impact) versus solo threshold (300>310w) where it could be the difference between blowing or not. Therefore, in a race where you spend a lot of time drafting, the importance of reliability, grip etc increases relative to rolling resistance.
So yes, it depends.
20 in the 2.1/2. 25ish in the 45.
eta: and with inserts as well.
I did the Gralloch on Thunder Burts, puncture free. On a set of the Nextie 30mm internal width rims, ran them at 21 psi front and 23 psi rear (I am 78kg). Several buddies of mine with smaller tyres had punctures, completely anecdotal and probably pure chance but given the nature of the punctures they had (sharp flint cutting in), I felt the lower the pressure the less likely a puncture was. There was not much in the way of danger of bottoming out to cause a pinch puncture.
Indeed, lower pressure is certainly a big factor in terms of puncture resistance, especially in resistance to cuts from sharp rocks. Imagine a balloon, blow it up to nearly bursting, and the slightest contact with a sharp object will cut it, then take the same balloon blown up to less pressure, now you can press a sharp object against it and it will resist cutting. So tire choice, and pressure, needs to be considered in terms of the balance of many factors.
Yeah interestingly I have heard a lot of people suggest you should run higher pressures than normal to prevent flats by skimming over the surface, but I’m in the same camp as you - lower is better and pinch flats are pretty unlikely on that course.
It is possible to survive on TBs, naturally… but I think they were a high risk tyre for that course.
Love this thread and thought I’d share some real world example. For the last few years I have done a gravel race called Seven in Western Australia, 125km and 3300m of climbing.
Comparing this year and last year I had pretty much the same NP and average power through each race but did change my tires. Last year I ran 45mm Schwalbe G One R’s front and rear. This year I ran the new Schwalbe G One R Pro 50mm in the rear and a Super Ground 2.1 Thunder Butt up front.
Despite carrying about 3 to 4kg more on me I managed a high number of PB’s and close Seconds across the course compared to last year. This year I ran pressures acrording to Silca’s guide and assumed cat 4 gravel. While the risk of flat here is quite low this year due to dry conditions the pea gravel was deep and like running on ball bearings. (one of the reasons local legend Sam Hill got so good)
I did run a speedsuit on course this year compared to last which would have an impact as well but average speed was only 23kph. But I am pretty convinced it was a marginal gain that helps on the day both in control in the decents and lower rolling resistance.
Depends what kind of flats you’re optimising to prevent, I guess. Lower pressure to reduce cut/puncture risk and higher pressure to reduce rim strikes and pinch flats. So both can be true…
Take a Thunder Burt vs your average gravel tire. Are we really claiming that
If so - what’s the mechanism that makes the Burt fast on the drum but slow on tarmac? Note we’re not talking about aero here - that part is well understood.
What about those new G-one Speed Pro(and older super ground) in 29x2.35” maybe they dont fit many frames but theyre fast.
I agree with all of that. Maybe I’m misinterpreting some claims but it does sound like people think the rolling resistance of mtb tires is higher on tarmac somehow - like in DJ’s test.
Yes - but the same point applies. The Race King is faster (or at least same CRR) on the drum than the Cinturato H it was compared with.
Unless I’ve missed some change in the laws of physics, there should be very few meaningful reasons that CRR on a road does not correlate to BRR drum speed.
That is exactly the point I was trying to make, sorry.
I understand the reasoning, I just don’t agree with it (or rather, it’s not applicable to the characteristics of this course to minimise puncture risk).