General Cycling Discussion - Tyres, speed - weight v rolling resistance
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09-02-03, 08:56 AM
A new set of tyres has set me thinking.
What has the most noticeable effect on speed - rolling resistance or weight? I'm assuming it's rolling resistance, and that the weight only really effects initial acceleration and climbing. The new tyres although heavier are slightly narrower and more rounded and feel faster over the short distances I've used them so far.
09-03-03, 09:22 AM
Come on folks - some of you must have a better grasp of physics than me ;)
Rolling resistance is proportional to the energy that goes into deforming the tires. (i.e. rolling resistance is the energy lost when flattening and unflattening the tire in contact with the ground)
The rolling resistance of the tires is really a complex function of the entire spring action of the tire as it deforms and returns to normal shape. The more efficient this 'spring' the less rolling resistance.
Higher pressures generally minimize the deformation and reduce resistance.
Smoother tires seem to reduce rolling resistance. This seems to be due to energy wasted in locally deforming the tread bumps on knobby tires, etc.
Harder compound in the tires would seem to suggest lower rolling resistance.
Weight difference between tires would have a very very minimal effect on rolling resistance, although anything which reduces the rotational inertia of the wheels will give the bike more acceleration for a given effort and may make it seem faster.
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