What did you use to arrive at those PSI numbers? Seems high to me…I haven’t played with any of the online calculators, but based on what I run for my 48’s (~20psi), I expect to be around 17psi for my Thunderburts. (Note - I tend to run lower psi than the online calculators)
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That’s pretty high. I’d take that down to 20/21 at the highest, then work down from there.
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I ride my 2.2 Race Kings at 17/19 at ~180#, albeit with inserts and on my XC Bike.
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According to Silca’s site for 190lbs, 52 mm, category 2 gravel, mid range casing tubeless, cat 1, 2, 3 racing, it specifies 24 psi/23 psi.
During my last race, which was significantly more gravel and also slightly rougher, I ran my 47 pathfinders (that measured 48) at 26/22 and felt pretty good with them. For really chunky gravel I had previously ran them around 24/21 and found that good.
The Thunder Burt rear at 24 felt low on the pavement/tamed sections, but pretty bouncy on the rougher sections.
Maybe I should actually weigh myself with all my gear/liquids etc. My bike is probably around 19, I’m 157 in the buff, and have the typical tools, 3 water bottles, etc. Not sure that there’s a big difference in tire pressure between 185 & 190.
Gravel bike weight is generally 60/40, so you don’t need more than 1-2 psi back/front.
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I think you are always gonna run into this situation when using a MTB tire for any extended paved sections. The challenge is whether to optimize for those sections or the gravel…
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Yeah, I would let some pressure out as some others have mentioned. The pressure is pretty much the same in all these test it is whatever the wolf tooth App recommends Or the silca one they are pretty similar. That is also why I haven’t listed individual weights and pressures for everything because there is only so much information worth packing in to the post on these. I’ve also been really careful with temperature inside versus outdoors As that can change the actual tire pressure once you are riding.
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Can I still use 50 mm plus tyres on a 19 mm internal wheel? Will I be better off sticking with my 45 mm?
I don’t really fancy buying new wheels yet as these are still working.
Has anyone does Chung testing on wider rim vs narrow rim?
That’s narrow enough where I would consider this more of a compatibility question than a performance question… To directly answer your question, though it has been studied!
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50mm would work, but you would likely need to run a higher pressure than is ideal to keep the tire from rolling in the corners. I think people forget/don’t know that the upper limit of how wide a tire can be is much further than modern news/trends would have you think. I used to run ikon 2.35s that measured almost 2.4 on 21.5mm mtb rims and rode them everywhere from super tame XC to black diamond bike park trails.
It may not be optimal for handling, aerodynamics, or rolling resistance, but it will definitely work.
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I was thinking that. I’m sure my old xc wheels were around 20 mm running 2.1 and 2.2 inch tyres. I wasnt as fussed about optimisation back then so never thought about it. Reading this I was getting worried about needing modern rims all ill be 10 watts down. I will look into keeping the hubs and relacing onto some mtb rims
I’m sure there might be reasons not to do this, but here’s the setup I run for more extreme “gravel” (class 3 and 4 according to the 1-4 system): a drop bar hardtail.
Lynskey GR300
I9 650b wheels
Conti Race King 27.5 x 2,2 in the front (this fits in a Rockshox Rudy Ultimate)
Schwalbe Thunder Burt 27.5 x 2.1
The RK has slightly better grip than the TB, so I can hold the line on faster descents.
While it’s mainly for riding on light MTB trails, it does double duty as a backup/winter road bike.
Well DJ’s latest video opens this up again, and I’m glad it does… if anything to show that you have to remain open minded and sceptical, a few studies do not make science.
With cobbles being an extremity for ‘bounce’ the right tyre is a much more nuanced decision than many here have suggested.
It’s a shame he added so much anecdotal evidence at the end though. The testing said a lot and he should have left it there.
Dylan’s new video has a lot of good info in it. And it absolutely shows that races where I live that can be 50/50 road/gravel do not need mtb tires. I get it for Big Sugar and Unbound, but you really have to look at the course you will ride or race on and make the best choice. So the answer for the thread title is, it depends. Case closed.
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Also the majority type of the gravel, the surface at critical race moments, etc. It’s clearly a spectrum and different tyres will perform best on different sections. The harder packed, the more it leans towards a narrow tyre (where speed is also faster) and vice versa. I’m glad this will never have an absolute answer.
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This really shouldn’t come as a surprise…a lot of us have been saying that for awhile.
Heck, even Dylan himself has noted that running MTB ties in BWR NC last year was probably a mistake since he got dropped on the road section.
IMO, your tire choice need to reflect the course, with a deference to running the widest tire you can and then sizing down depending on the characteristics of the course.
Right, it’s not a surprise at all. Most of us have been saying this all along, but there has absolutely been a contingent that was all in on mtb tires as the overall best choice, including Dylan when he made that mistake at BWR NC. He ran the WRONG tires because he had an all or nothing mindset versus the more complicated shades of gray that actually exist.
What I’d like to see now is the results Dylan had used to make charts for 50/50 gravel/road, 30/70, 70/30, etc… The 50/50 seems easy. You take the pavement RR figure and add it to the cobbles RR number and divide it by 2 since both would be half the course. I think? Then you get a RR number for the total course and can choose what is best. How can we do that for other percentage breakdowns though?
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Yup, I mentioned this as one of the flaws in his previous testing (admittedly form a few years ago). He did some testing at Unbound on some segments but then used it for the analysis on the whole course. Well if you only test on the chunky stuff, but there is a fair amount of tamer gravel or asphalt, you may not be making the best tire choice.
Similarly, the gravel that I normally ride is (at best) Cat. 1 gravel…so a MTB tire may not be the best choice.
All that said, I think the real change in thinking here is that we generally used to start from a narrow tire mindset and then start adding width if the course was chunky. Based on recent data and testing, it seems we are now tackling the challenge from the other side - assume the widest tire you can run and then narrow down if needed.
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The BWR NC race is more complicated than he made it out. He got dropped on the pavement after unpaved Pinnacle Mountain road. Given the state of that unpaved section it’s as likely, perhaps more, that he would have been dropped there or earlier on the pavement if he’d been on smaller tires.
DJ and the Bonk Bros have a fair understanding of what the testing says, but they all seem to struggle with the actual factors that are at play in the real world and the tests are trying to tease out as proxy. Or at least they struggle to explain on the podcast.
As was said above “a few studies do not make science” and it’s hard to draw a concrete conclusion from one instance in one race by one rider. I rode larger tires for the races that I felt called for it this year and so far my results are better than years past, with about the same fitness and otherwise equipment/position.
If you go back and look, my first post in this thread was a “no” to the thread title, which became a “yes” the more I read and rode. I’ve been a flip-flopper on this for a long time so DJ’s current vid is more information to obsess over, which I like. Gravel tires are getting much better and it seems clear that in the future we will see more clearly delineated bike types, and tire choice metrics.
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I agree with the “it depends” comments.
My first thought about calculating for mixed surface courses (e.g. 70% road, 30% gravel) using simple math would be to weight the different resistances based on time spent (not distance) on each surface. So you also have to make an assumption about average speed on each surface. But that shouldn’t be too difficult to estimate.
While I agree with others about potential “decisive moments”, this is trickier because it’s not just about the moment, it’s about everything you do leading up to it that matters as well.
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