Wider Tires Roll Faster
I'm wondering what opinionated Chainlinkers make of this study:
http://janheine.wordpress.com/2012/06/13/bicycle-quarterly-performa...
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Replies to This Discussion
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Permalink Reply by Lanterne Rouge on -
Science! How does it work?!
Wider tires are much more comfortable. I am reminded of that when I ride my hybrid with 32mm tires.
I will agree with this much: wider tires roll faster than skinnier tires *at the same pressure*.
naturally a 32mm tire will roll faster than a 23mm tire with both at 85 psi.
It's a good thing I don't care about speed one bit.
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Permalink Reply by Cameron 7.5 mi on -
I'm surprised that a tire with a supple casing was a faster tire. Since deformation of the casing is one of the main sources of energy loss, I would have expected a rigid casing to be faster. One possible explaination is that the stiff casing deforms as much as the supple casing, but requires more energy to do so.
With the widths he was comparing (23mm vs 25mm), I'm not overly surprised that the wider tires performed better. Again the deformation of the casing is the main source of energy loss. The tire must deform until (contact area) x (pressure) = (weight of bike and rider). With a wider tire the contact area starts wider, and therefore the casing doesn't need to deform as much to create the required contact area. I would except tires that start wider than a skinny tire's contact area to have little to no benefit.
Disclaimer: I don't have any sources or studies to back any of that up, except the reasoning I gave above. If anyone knows of any research supporting or refuting anything I said, I'd be interested in reading it.
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Permalink Reply by Jeff Schneider on -
A more supple casing is the reason tubular tires are so much easier to push than clinchers, I think. While the tire itself may absorb more energy from deformation, the fact that the bicycle as a whole is deflected less (and so loses less kinetic energy) by small bumps makes these tires more efficient.
I would guess that wider tires do have less rolling resistance *at a given pressure* because they also have less deformation at a given pressure.
The main disadvantage of wider tires is that they require wider (and hence heavier) wheels, which require more energy to get going from a stop.
The best result is gained IMO from using a tire width appropriate for the roughness of the road surface. Where there are larger bumps, a narrow tire just can't absorb the deflection.
For short rides in the city, none of this makes much difference compared to the fact that most people ride on seriously underinflated tires, have rusty chains, derailleurs that are far out of adjustment, incorrect saddle height/tilt, etc...
Cameron Puetz said:I'm surprised that a tire with a supple casing was a faster tire. Since deformation of the casing is one of the main sources of energy loss, I would have expected a rigid casing to be faster. One possible explaination is that the stiff casing deforms as much as the supple casing, but requires more energy to do so.
With the widths he was comparing (23mm vs 25mm), I'm not overly surprised that the wider tires performed better. Again the deformation of the casing is the main source of energy loss. The tire must deform until (contact area) x (pressure) = (weight of bike and rider). With a wider tire the contact area starts wider, and therefore the casing doesn't need to deform as much to create the required contact area. I would except tires that start wider than a skinny tire's contact area to have little to no benefit.
Disclaimer: I don't have any sources or studies to back any of that up, except the reasoning I gave above. If anyone knows of any research supporting or refuting anything I said, I'd be interested in reading it.
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Permalink Reply by Michael A on -
All this aside, the Giro (second largest bike race in the world) came down to the time trial and was won by a mere 30 seconds, every single rider in the top 20 used 19-21 mm wide tires. These are the men who race and ride at the top limits of human power, not some dude in a wind tunnel or in front of a computer.
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Permalink Reply by ilter on -
Haha, Jan Heine finally made it to the Chainlink :)
In comments section, he gives an explanation as to why.. he says deformation is less w/ wider tire because the contact patch is shorter, assuming same pressure.
I also remember reading (either in this same blog or his Bicycle Quarterly magazine) that skinny tires at very high pressures cause energy loss in rough pavement, as they transfer road vibration/bumps to vertical movement, whereas thicker tires absorb more & not transfer it to the bike & rider.. something in those lines..
Edit: I realize I mostly rephrased what Jeff already said above. oh well :)
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Permalink Reply by ilter on
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Did you read the details ? I think this dude is different & may convert you too :)
Michael A said:
All this aside, the Giro (second largest bike race in the world) came down to the time trial and was won by a mere 30 seconds, every single rider in the top 20 used 19-21 mm wide tires. These are the men who race and ride at the top limits of human power, not some dude in a wind tunnel or in front of a computer.
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Permalink Reply by Michael A on
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I have been cycling a long, long, time When I started racing there were only tubulars, we would train on 21mm tires and race on 18-19 mm. I now train and race on both tubular and clincher 21-23 mm tires. I commute on 28mm high perf tires on my cross bike. With the right tubular tire you and the right pressure you get unmatched comfort and performance.
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Permalink Reply by ilter on
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I see. Which type of tire do racers use these days ? I think JanHeine`s research is all clinchers.
Michael A said:I have been cycling a long, long, time When I started racing there were only tubulars, we would train on 21mm tires and race on 18-19 mm. I now train and race on both tubular and clincher 21-23 mm tires. I commute on 28mm high perf tires on my cross bike. With the right tubular tire you and the right pressure you get unmatched comfort and performance.
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Permalink Reply by Allen Wrench on -
I don't care how fast my tires are up to a certain point, so grain of salt. But it's fun to see Jan Heine's nerdy article cited here... He rode on a rumble strip with an ergometer hooked to the bike.
There was a companion piece to this if I remember right saying that "low" pressures like 85 psi roll faster than the common 120 psi or so as soon as there is any bumpiness in the road (and almost the same if the road is smooth). The argument for that was, as Ilter noted, that the thing that has to move when you hit a bump is the entire bike and rider, for the high pressure tires, or for the lower pressure tires it's only the little piece of rubber in the contact area. Additionally, the movement of the tire rubber in the latter case is more elastic since it's sprung by the air inside, and you get most of the energy back out again. If I recall right, the narrow tires don't do as well at that elastic thing since they hold less air. The floppier sidewalls convert less springy energy to heat than thick ones do so they're supposed to be better too, though I seem to remember that didn't make as much difference.
If you think high pressure tires are most efficient why not take it to an extreme and get solid rubber wheels?
Remember Jan Heine is a fan of randonneur biking, not criterion road racing, so maybe he's not without bias.
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Permalink Reply by James BlackHeron on -
Skinny tires and skinny jeans are hip. If you don't conform you are not cool.
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Permalink Reply by Duppie 13.5185km on -
Nice article. but rather meaningless for the majority of bicyclists because it completely ignores real-life considerations like: comfort, durability, puncture resistance, availability and most importantly: price.
It's like testing a bunch of race cars and proving that a certain design element really improves acceleration. Moot point if your are have to transport a family of four.
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Permalink Reply by Kelvin Mulcky on -
Anyone see the article in print? I'm more interested in 30mm vs. 25mm than 23mm x 25mm.
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