3 ms·

This is not a new theoretical result, but it is a new practical reality. Tires are built differently today due to better materials like multi-layer puncture-res

by jl2718 7y ago

This is not a new theoretical result, but it is a new practical reality. Tires are built differently today due to better materials like multi-layer puncture-resistant weaves. It used to be a thick layer of rubber in the middle and relatively weak sidewalls, so the contact profile would be nearly cylindrical. Lower pressures were awful, and the sidewalls would blow out on a bigger tire above 60psi. There are a few other differences that matter a lot in the peloton. Power transfer is important for holding a tight draft. A pro on 28s will definitely notice a delayed/muted impulse response over 23s. I believe this also affects pedaling efficiency, as any MTB racer on a soft tail will attest. Narrow tires also give much better handling/braking and therefore much faster descents. Fat tires braking gives this weird kick-back that feels like it’s tossing you over. Still, I ride fatties. I love the way they smooth out the road. But they’re not necessarily faster.

tokai 7y ago
The width is crawling upwards for the pro riders. No sub 25mm tire was used in the Tour de France the last two years, iirc. I can't see them going over 30mm though. The article underplays aerodynamics in my opinion.
- SkyMarshal 7y ago
  Any idea if pro riders increasing their tire size is associated with them also transitioning to disk brakes? Disks solve at least half the problem - braking. (Narrow tires may still handle better in other ways though).
  - tokai 7y ago
    Yeah, disk breaks are definitely helping the trend. From the head mechanic of EF Education last year: «The disc-brake thing has gained real momentum, so on those frames you can certainly run wider tires because there's the clearance for it. I could see it evolving to 26mm or 27 mm as the standard road-racing tire, sure. Why not.» https://www.businessinsider.com/tour-de-france-wider-tires-lower-pressure-faster-2018-7?r=US&IR=T https://www.businessinsider.com/tour-de-france-wider-tires-l...
frabbit 7y ago
contact profile would be nearly cylindrical How would a 2-dimensional contact profile be describable with a 3-dimensional object? A pro on 28s will definitely notice a delayed/muted impulse response over 23s. Really? Is this a measured, observable fact or another piece of woo that cyclists have believed for donkeys' years? I believe this also affects pedaling efficiency, as any MTB racer on a soft tail will attest. Are you seriously claiming that bouncing up and down on a rear-suspended MTB is comparable to riding on a 622-28 inflated to 620kPa ? Narrow tires also give much better handling/braking and therefore much faster descents. Fat tires braking gives this weird kick-back that feels like it’s tossing you over. Again, I have to ask for specifics and measurements. I will counter-claim that that the inferior response of over-inflated narrow tires to road imperfections leads to much more jittery descents and inferior handling on most surfaces, ths leading to slower descents (that's what all the Bicycle Quarterly tests of roll-downs are about).
_Wintermute 7y ago
As a competitive cyclist and someone who spends far too much time thinking and talking about bikes, I've never heard any of these claims, and in fact most of them are the opposite of the common consensus among cyclists.

by jl2718 7y ago

tokai 7y ago

The width is crawling upwards for the pro riders. No sub 25mm tire was used in the Tour de France the last two years, iirc. I can't see them going over 30mm though. The article underplays aerodynamics in my opinion.

SkyMarshal 7y ago
Any idea if pro riders increasing their tire size is associated with them also transitioning to disk brakes? Disks solve at least half the problem - braking. (Narrow tires may still handle better in other ways though).
- tokai 7y ago
  Yeah, disk breaks are definitely helping the trend. From the head mechanic of EF Education last year: «The disc-brake thing has gained real momentum, so on those frames you can certainly run wider tires because there's the clearance for it. I could see it evolving to 26mm or 27 mm as the standard road-racing tire, sure. Why not.» https://www.businessinsider.com/tour-de-france-wider-tires-lower-pressure-faster-2018-7?r=US&IR=T https://www.businessinsider.com/tour-de-france-wider-tires-l...

frabbit 7y ago

contact profile would be nearly cylindrical How would a 2-dimensional contact profile be describable with a 3-dimensional object? A pro on 28s will definitely notice a delayed/muted impulse response over 23s. Really? Is this a measured, observable fact or another piece of woo that cyclists have believed for donkeys' years? I believe this also affects pedaling efficiency, as any MTB racer on a soft tail will attest. Are you seriously claiming that bouncing up and down on a rear-suspended MTB is comparable to riding on a 622-28 inflated to 620kPa ? Narrow tires also give much better handling/braking and therefore much faster descents. Fat tires braking gives this weird kick-back that feels like it’s tossing you over. Again, I have to ask for specifics and measurements. I will counter-claim that that the inferior response of over-inflated narrow tires to road imperfections leads to much more jittery descents and inferior handling on most surfaces, ths leading to slower descents (that's what all the Bicycle Quarterly tests of roll-downs are about).

_Wintermute 7y ago

As a competitive cyclist and someone who spends far too much time thinking and talking about bikes, I've never heard any of these claims, and in fact most of them are the opposite of the common consensus among cyclists.