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Is the data available somewhere ? It doesn’t match my experience at all. I have a road bike and a gravel bike - same quality range (gravel slightly higher). At

Is the data available somewhere ? It doesn’t match my experience at all. I have a road bike and a gravel bike - same quality range (gravel slightly higher). At low speeds, that may be true - the difference is negligible. But at higher speeds / power outputs, the road bike beats the gravel hands down - by a significant margin (big enough to be felt, without a power meter)

brianwawok 5y ago
Does your gravel bike have road slicks? Is your geometry the same, i.e. your reach and drop is the same?
- TheAlchemist 5y ago
  No. Fair point indeed - the tires are not the only difference. I suspect they are one of the biggest though (based on subjective feeling - for what it’s worth).
  - reubenmorais 5y ago
    It's almost physically impossible for the tires to be a bigger difference than geometry (and thus your position), specially at faster speeds as you mentioned, because aerodynamics quickly dominate the overall resistance you're fighting to keep your speed.
derbOac 5y ago
My impression from reading articles and technical reports about this is that there's a couple of things going on. First, I think the wider-tires-are-faster argument has to be appreciated in the context of the narrow-tires-are-faster argument that dominated for a long time. With the latter paradigm, you wanted your tires as narrow as possible, with some lower boundary constraint due to wheel and tire thinness limitations, maybe around 20-21mm. The former paradigm emerged in part in contrast to that, in that "wider" doesn't mean "infinitely wide" but rather "wider than what's typical for people striving for narrower tires". Some of the arguments about rolling surface area are maybe understood in that context -- the patch of tire in contact with the road maintains the same area as a minimal area under the narrow tire paradigm, and then it starts to become larger, at which point you start increasing friction theoretically with more tire surface area in contact. The other argument for wider tires is about impedance gains due to wider tires -- decreased vibrations basically. This is different than decreased or equal rolling resistance per se. However, there are eventual aero losses for wider tires, as well as weight increases (which then increase rolling resistance). Eventually these aero losses and weight increases overshadow any impedence gains, and the wider tires' costs exceed their benefits. This is the sort of thing about cycling that is frustrating to me. I love cycling, but so many mechanical factors get really oversimplified: costs aren't often realistically assessed against actual gains, and sometimes gains are very restricted in the circumstances under which they apply. Disc brakes, for example, are safer, but you see little discussion about whether the safety margin they afford actually would make any practical difference in scenarios in which accidents typically occur (e.g., where a car is coming from the side or a blindspot), and they're often heavier and less aero (so yes, they save your carbon wheels, but you almost have to have deep section carbon wheels to make up for their weight and aero costs to begin with). I'm not saying disc brakes are a bad thing, but I think in practice their gains are more complex than is often made out to be. In the same way, wider tires are probably more optimal than a lot of people thought in, say, 1985. But I think the pendulum has swung a bit too indiscriminately in the other direction at the moment. What's probably most accurate is to say you want the widest tire that affords some impedence gains given your typical riding surface, and not anything wider. Aero effects increase exponentially (?? polynomially?) with speed (that is, as your speed increases, aero effects become more of a factor in further speed increases), which would match your experience. As your speed increases, the wider tires become more and more of a burden, and require higher wattage to compensate for. All sports with any significant tool involved are full of misperceptions and myths, not supported by science. Cycling is full of them, but it's not the only athletic discipline like that.
sjburt 5y ago
This is an old article that compares tires in the 20-25mm range. The bike industry has moved to wider tires and 25 or 28mm tires are now quite common on road bikes, and gravel bikes have much wider tires. I would be the optimum is around 25 or 28 for road bikes on typical roads, especially as aerodynamics become a bigger factor.
wiredfool 5y ago
They (Jan and the RH crew) have done several versions of this over the years, and the takeaway is that some gravel bikes feel slower due to geometry, rider position, Q factor, and so on, but the tire width isn’t a factor. (I think one was testing the open vs firefly, with similar riding positions but drastically different wheels)
- et-al 5y ago
  Don't forget Jan's signature word: planing. This is prob the Open vs Firefly test you're thinking of: https://www.renehersecycles.com/what-makes-a-bike-fast/ https://www.renehersecycles.com/what-makes-a-bike-fast/ In the test, they apparently isolated the wheel weight by swapping out wheels on the slower-on-paper Firefly and the bike didn't ride up the hill significantly faster. However Jan Heine's experiments are often pseudo-sciencey and subject to rider effort. In this test, there were no power meters to show the difference in rider efforts between the two bikes. But somehow planing gives you free watts.
  - jmilloy 5y ago
    Yeah, the lack of power meter data in their tests is really frustrating.
  - wiredfool 5y ago
    Jan has a PhD in a science (geo I think), and has done bike experiments with Jim Papadapolis. I would generally take his experiments over most random ones cited on the net. Gospel truth? No. Probably not. Generally pretty good if you look at what he’s actually testing? I think so. (Disclaimer, Jan was a teammate 25 years ago, and apart from not having talked since then, I’d consider him a friend)
gnopgnip 5y ago
https://www.bicyclerollingresistance.com/ https://www.bicyclerollingresistance.com/ compares some different tires.
- oriolid 5y ago
  Jan Heine's whole claim is that these tests are wrong and his method reveals the truth. It's so frustrating that he doesn't test any mainstream tires so we don't even see how the results match.
nabilhat 5y ago
Absolutely, Jan isn't the only one running some numbers, nor the most objective / consistent. Here are two sets of better measurements on a range of sizes of a single tire model, on the same wheel, over a range of pressures, with precise measurements of critical factors like tread depth, sidewall thickness, tread thickness, real world actual width, and actual rolling resistance measured in watts: https://www.bicyclerollingresistance.com/specials/conti-gp4000s-ii-23-25-28 https://www.bicyclerollingresistance.com/specials/conti-gp40... https://www.bicyclerollingresistance.com/specials/schwalbe-marathon-32-37-40-47 https://www.bicyclerollingresistance.com/specials/schwalbe-m... So, wider tires mean you can run a comfier lower pressure at the same rolling resistance. Looking through the rest of this site, it's also super clear that there are far more significant factors to rolling resistance than width. It's practically criminal this site doesn't get tons of attention!
jmilloy 5y ago
This article is really a summary, as part of a series on myths in cycling. Here's a pair of much more recent article with more data and methodology and nuance specifically about testing and speed: https://www.renehersecycles.com/how-we-test-tires/ https://www.renehersecycles.com/how-we-test-tires/ https://www.renehersecycles.com/bq-tire-test-results/ https://www.renehersecycles.com/bq-tire-test-results/

brianwawok 5y ago

Does your gravel bike have road slicks? Is your geometry the same, i.e. your reach and drop is the same?

TheAlchemist 5y ago
No. Fair point indeed - the tires are not the only difference. I suspect they are one of the biggest though (based on subjective feeling - for what it’s worth).
- reubenmorais 5y ago
  It's almost physically impossible for the tires to be a bigger difference than geometry (and thus your position), specially at faster speeds as you mentioned, because aerodynamics quickly dominate the overall resistance you're fighting to keep your speed.

derbOac 5y ago

My impression from reading articles and technical reports about this is that there's a couple of things going on. First, I think the wider-tires-are-faster argument has to be appreciated in the context of the narrow-tires-are-faster argument that dominated for a long time. With the latter paradigm, you wanted your tires as narrow as possible, with some lower boundary constraint due to wheel and tire thinness limitations, maybe around 20-21mm. The former paradigm emerged in part in contrast to that, in that "wider" doesn't mean "infinitely wide" but rather "wider than what's typical for people striving for narrower tires". Some of the arguments about rolling surface area are maybe understood in that context -- the patch of tire in contact with the road maintains the same area as a minimal area under the narrow tire paradigm, and then it starts to become larger, at which point you start increasing friction theoretically with more tire surface area in contact. The other argument for wider tires is about impedance gains due to wider tires -- decreased vibrations basically. This is different than decreased or equal rolling resistance per se. However, there are eventual aero losses for wider tires, as well as weight increases (which then increase rolling resistance). Eventually these aero losses and weight increases overshadow any impedence gains, and the wider tires' costs exceed their benefits. This is the sort of thing about cycling that is frustrating to me. I love cycling, but so many mechanical factors get really oversimplified: costs aren't often realistically assessed against actual gains, and sometimes gains are very restricted in the circumstances under which they apply. Disc brakes, for example, are safer, but you see little discussion about whether the safety margin they afford actually would make any practical difference in scenarios in which accidents typically occur (e.g., where a car is coming from the side or a blindspot), and they're often heavier and less aero (so yes, they save your carbon wheels, but you almost have to have deep section carbon wheels to make up for their weight and aero costs to begin with). I'm not saying disc brakes are a bad thing, but I think in practice their gains are more complex than is often made out to be. In the same way, wider tires are probably more optimal than a lot of people thought in, say, 1985. But I think the pendulum has swung a bit too indiscriminately in the other direction at the moment. What's probably most accurate is to say you want the widest tire that affords some impedence gains given your typical riding surface, and not anything wider. Aero effects increase exponentially (?? polynomially?) with speed (that is, as your speed increases, aero effects become more of a factor in further speed increases), which would match your experience. As your speed increases, the wider tires become more and more of a burden, and require higher wattage to compensate for. All sports with any significant tool involved are full of misperceptions and myths, not supported by science. Cycling is full of them, but it's not the only athletic discipline like that.

sjburt 5y ago

This is an old article that compares tires in the 20-25mm range. The bike industry has moved to wider tires and 25 or 28mm tires are now quite common on road bikes, and gravel bikes have much wider tires. I would be the optimum is around 25 or 28 for road bikes on typical roads, especially as aerodynamics become a bigger factor.

wiredfool 5y ago

They (Jan and the RH crew) have done several versions of this over the years, and the takeaway is that some gravel bikes feel slower due to geometry, rider position, Q factor, and so on, but the tire width isn’t a factor. (I think one was testing the open vs firefly, with similar riding positions but drastically different wheels)

et-al 5y ago
Don't forget Jan's signature word: planing. This is prob the Open vs Firefly test you're thinking of: https://www.renehersecycles.com/what-makes-a-bike-fast/ https://www.renehersecycles.com/what-makes-a-bike-fast/ In the test, they apparently isolated the wheel weight by swapping out wheels on the slower-on-paper Firefly and the bike didn't ride up the hill significantly faster. However Jan Heine's experiments are often pseudo-sciencey and subject to rider effort. In this test, there were no power meters to show the difference in rider efforts between the two bikes. But somehow planing gives you free watts.
- jmilloy 5y ago
  Yeah, the lack of power meter data in their tests is really frustrating.
- wiredfool 5y ago
  Jan has a PhD in a science (geo I think), and has done bike experiments with Jim Papadapolis. I would generally take his experiments over most random ones cited on the net. Gospel truth? No. Probably not. Generally pretty good if you look at what he’s actually testing? I think so. (Disclaimer, Jan was a teammate 25 years ago, and apart from not having talked since then, I’d consider him a friend)

gnopgnip 5y ago

https://www.bicyclerollingresistance.com/ https://www.bicyclerollingresistance.com/ compares some different tires.

oriolid 5y ago
Jan Heine's whole claim is that these tests are wrong and his method reveals the truth. It's so frustrating that he doesn't test any mainstream tires so we don't even see how the results match.

nabilhat 5y ago

Absolutely, Jan isn't the only one running some numbers, nor the most objective / consistent. Here are two sets of better measurements on a range of sizes of a single tire model, on the same wheel, over a range of pressures, with precise measurements of critical factors like tread depth, sidewall thickness, tread thickness, real world actual width, and actual rolling resistance measured in watts: https://www.bicyclerollingresistance.com/specials/conti-gp4000s-ii-23-25-28 https://www.bicyclerollingresistance.com/specials/conti-gp40... https://www.bicyclerollingresistance.com/specials/schwalbe-marathon-32-37-40-47 https://www.bicyclerollingresistance.com/specials/schwalbe-m... So, wider tires mean you can run a comfier lower pressure at the same rolling resistance. Looking through the rest of this site, it's also super clear that there are far more significant factors to rolling resistance than width. It's practically criminal this site doesn't get tons of attention!

jmilloy 5y ago

This article is really a summary, as part of a series on myths in cycling. Here's a pair of much more recent article with more data and methodology and nuance specifically about testing and speed: https://www.renehersecycles.com/how-we-test-tires/ https://www.renehersecycles.com/how-we-test-tires/ https://www.renehersecycles.com/bq-tire-test-results/ https://www.renehersecycles.com/bq-tire-test-results/