Is a MTB tire the fastest and best tire for Gravel racing?

Imagine if Lachlan Morton wasn’t running a 44mm Vittoria rear when he won unbound last year. Math says he’d have been like, 15-20 minutes faster.

Or if Keegan wasn’t sponsored by Maxxis, a company that never comes in near the top of any rolling resistance lists.

A bit of sarcasm above, but between these general examples in the insanely conflicting data between test methods and results, it certainly backs off a lot of (what previously seemed like) absolutes. I can fit 2.1’s on my bike with enough clearance for dry conditions, but certainly starting to feel like going back to a 47 pathfinder as a general “all around” pavement/gravel tire doesn’t seem like it’ll leave me in the dust that it once did.

After doing an all out solo effort on my thunder Burt’s that were 50/50ish road/gravel conditions, my speed did seem an about 1/2 mph slower than I would have expected.

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I personally would not run TB 2.1’s on a course like that…

As for the claims of time savings, focusing on the absolute number is like focusing on time savings from aero kit…of course you are not going to save XX-specific amount of time. But directionally, you can ascertain which gear choices are faster…and if you have to run tires or a helmet, you may as well pick faster options, whatever the actual times savings will be.

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According to BRR, it seemed that the thunder burt had a lower rolling resistance than mostly all/all 45mm tires. I don’t know that BRR differentiates between conditions in their testing and the conditions would mostly mimic pavement. Maybe I was entirely misinformed, although I follow the topic pretty closely.

It didn’t really seem until DJ’s most recent video actually comparing the conditions of the pavement vs cobbles that it became more evident.

I seem to recall maybe even in this thread people mentioned that tires like the TB & RK were faster than the higher rolling resistance (pet BRR) narrower tires on pavement.

I could probably argue that rolling resistance is more important than aero savings in some ways. Of course, as you mentioned, optimize both.

However, rolling resistance is in 100% effect the entire race. Aero gains are significantly limited when drafting in a group.

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I’m not arguing for one over the other…just pointing out that I only look for at claimed time savings directionally, not for actual time savings.

So if the data says that Helmet X is 20" seconds faster in a 40K TT than other helmets, I’m gonna accept the direction that it is a faster helmet and not worry too much about what the actual times savings will be.

Similarly, I will use a wider tire because the data suggests consistently that it will be faster on gravel, so I’ll use a wider tire. Do I believe a ThunderBurt 2.1 is gonna save me 26 minutes over 100 miles? Hell no…but I believe it is going to save me time overall and since I need to have tores, I might as well choose what appears to be one of the fastest tires out there.

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I’m if I should save 26 min with TB2.1 I would assume I see 50% of that savings in real world

I just mounted up an old set of Race Kings on my MOG - and they definitely fit for dry conditions although I need to take actual clearance measurements. Makes it look like a really cool Monster Truck of a Gravel Bike.

I probably do need to have another option available though for Unbound. I’m guessing that the clearance isn’t enough if it gets sloppy. Schwalbe does have the Burt, Ray, Ralph, Rocket Ron all in 2.1 and many of their tires run small…

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Is it true that aero gains are limited when drafting? I think aero gains allow you to use fewer watts even when drafting. Or am I mistaken?

Yeah depending on the group it decreases relevant CdA (aero drag) a good bit. But it is scalar as you hinted at for sure.

Best start with best you can get as it stays relevant even in the draft, just not as much as when out front.

This shifts the bias to rolling resistance importance, same as courses with more elevation change.

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Aero gains are severely limited when drafting because the air resistance part of the overall resistance that you need to overcome is significantly reduced. Not only that, but when drafting you are typically working sub-threshold where every watt saved is less valuable (e.g. 190w instead of 200w is far less impactful than 290w instead of 300w).

It’s why people sit up when drafting.

I know a couple guys who tried the Burt and unbound, and all flatted at least once

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Yeah, I’ve heard that about the Burt which is the reason I’ve never used it.

Currently I’m leaning towards Race King, or if I have to go narrower something like a 2.1 Ray/Ralph before dropping back to something like a Thundero 44/48 if Mud looks like it’s going to be a real issue.

Need to measure, I have more clearance than I thought I would.

Read the cycling news article. Sounds like the widest and most supple tire will be the fastest.

I don’t have access to the article. Do you know what pressures they ran those at?

Each tyre was set up to a pressure determined using SRAM’s online pressure calculator, inflated using a digital track pump and verified by a standalone tyre pressure gauge. Both the Panaracer tyre casing test cohort and the Pirelli models were all 40c in width, so an identical pressure was used for a great many of the tyres on test.

Even if we don’t take the 33c option out, the fastest tyre width at both 7m/s and 9m/s was the giant 2.1” option, with a saving of 5.9 watts per tyre at 7m/s and 6.5 watts per tyre at 9m/s, comparing the 31c to the 2.1”. That’s an 11.8-watt difference for a pair, or 13 watts at 9m/s for two tyres across the whole range.

In aerodynamic terms, while we did not take these setups into the wind tunnel ourselves we are able to draw on the work of others. Dylan Johnson, professional gravel racer and YouTuber, also recently undertook his own tyre testing at the SSE Hub, and while his tests involved different parameters, speeds, and setups to ours, he did also put his own race bike in the wind tunnel with varying tyre sizes. At 36km/h he found a 5.5 watt penalty moving from a 40mm to a 50mm Pirelli Cinturato H, but was also at pains to point out that his tests of the 2.2in (56mm) Continental RaceKing actually tested faster than the 50mm Pirellis, perhaps due to the sidewall texture, at least showing there is more to aerodynamics than simple frontal area calculations.

Cumulatively then, accounting for choosing a faster tread and the fastest width, we are currently looking at a total rolling resistance difference of around 20 watts on a smooth surface, and likely more on a rough one, moving from a narrower knobbly tyre to a larger, more slick option.

At more reasonable speeds - below 30km/h, so essentially everything below top-end gravel racing - the gains will be even greater, as the impact of aerodynamics, while still important, will play a lesser role in the overall picture than it does at fast road riding speeds. Essentially, as a rule, you should fit the widest tyres you can, and if you’re buying a new bike then the maximum tyre clearance should be a key consideration. Not only will you be faster in almost all scenarios, but you will be more comfortable, and have better grip too

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It seems like that information cherry picks content from numerous sources. Initially comparing the 33c to 2.1” stating that the 2.1” is faster (on what I assume is smooth conditions, based on the last paragraph).

Then referencing DJ’s latest video, where he very specifically mentioned that on pavement, the 2.2” is a pretty huge penalty over the narrower gravel tires.

I think if there is one thing we are learning is that apparently the testing methods for rolling resistance leave a lot to be desired and are far from accurate. Also, some of the studies would probably be better off testing at like 18/21 mph vs like 21/26 mph (or whatever the actual numbers), considering that like 95% of people actually relying on this data will spend a lot more time at 18 mph than 26 mph… Granted, the above does meters/seconds, because frequently going between km/mph isn’t quite enough lol.

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Yeah, i found the article bulky.

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Yeah. It’s tough to present. I’m using 15 mph medium gravel and 20 mph medium gravel to show wattages along with 17 mph road and 22 mph road. They seem to make the most sense to me from looking at mid pack and pro speeds On gravel bikes.

That testing rig still kind of boggles me … But the wattage numbers on the road tires they tested on their website Was pretty close to BRR, aero coach, and what I’ve had doing them outside. Thanks so much for the extra information there!!

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Sooo Pathfinder Pro 47 vs Thunderoo 48 for a front tire. I’m thinking thunderoo 44 for the rear of my revolt. I need a new front and eventually a rear but that can wait a bit.

Having ridden both extensively, I would say the Thundero 48’s, hands down. Suppler casing, smoother ride and better traction (note that most of the gravel I ride is hardpack w/ kitty litter, so a smoother tread like the Pathfinder can get a little sketchy at times).

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As a fellow newer Revolt owner, what rim widths and tires did you try that with?

I have 30mm internal and I was a bit concerned about using 2.2/2.25 like a Rocket Ron/Race King combo. I thought I might need to stay at 2.1.

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