4 ms·

Too high pressure actually decreases efficiency. While you have less deformation of the rubber, it causes the bike to bounce over irregularities more. The energ

by cultus 8y ago

Too high pressure actually decreases efficiency. While you have less deformation of the rubber, it causes the bike to bounce over irregularities more. The energy from this bouncing is lost. On rougher roads, often pressures below 90 PSI are best.

toxik 8y ago
Ok, yes, assuming traction isn't lost, stiffer is better -- really, smaller contact area is better, but that translates into stiffness. Then there is heat loss to tire deformation, of course.
- cultus 8y ago
  Stiffness in a tire is bad. That's why more expensive tires are suppler. Energy lost due to rolling resistance on a paved road is primarily viscous dissipation due to flex of the tire. If the tire is a stiffer material, this dissipates more energy. In addition, suppler tires deform over obstacles more readily, reducing bouncing and vibration. More or less, your contact patch is pressure/weight, since the tire can't support much weight on its own. It's going to be almost the same no matter what (slick) tire you are running. Wider tires have less rolling resistance for the same pressure (to a point), since the tire deflects less to maintain the same contact patch. Two tires of the same width, one stiff and one supple, will have to bend in the same way, and have nearly identical contact patches. However, the supple one will dissipate less heat doing this.
ema 8y ago
As a casual cyclist 50 psi already feels like "this is amazing I just hope my tires aren't gonna burst". So it seems "higher is better" is solid advice for most people, who aren't gonna go over 90 psi anyway.
- cultus 8y ago
  On a road bike, you will get a pinch flat from running tires that low, where the tube gets cut between the rim and the ground. Recommended pressure always varies. With wider tires, you typically must run them lower, since a too-high pressure will cause the tire to blow off the rim.

by cultus 8y ago

toxik 8y ago

Ok, yes, assuming traction isn't lost, stiffer is better -- really, smaller contact area is better, but that translates into stiffness. Then there is heat loss to tire deformation, of course.

cultus 8y ago
Stiffness in a tire is bad. That's why more expensive tires are suppler. Energy lost due to rolling resistance on a paved road is primarily viscous dissipation due to flex of the tire. If the tire is a stiffer material, this dissipates more energy. In addition, suppler tires deform over obstacles more readily, reducing bouncing and vibration. More or less, your contact patch is pressure/weight, since the tire can't support much weight on its own. It's going to be almost the same no matter what (slick) tire you are running. Wider tires have less rolling resistance for the same pressure (to a point), since the tire deflects less to maintain the same contact patch. Two tires of the same width, one stiff and one supple, will have to bend in the same way, and have nearly identical contact patches. However, the supple one will dissipate less heat doing this.

ema 8y ago

As a casual cyclist 50 psi already feels like "this is amazing I just hope my tires aren't gonna burst". So it seems "higher is better" is solid advice for most people, who aren't gonna go over 90 psi anyway.

cultus 8y ago
On a road bike, you will get a pinch flat from running tires that low, where the tube gets cut between the rim and the ground. Recommended pressure always varies. With wider tires, you typically must run them lower, since a too-high pressure will cause the tire to blow off the rim.