Originally Posted by
TimEarl
Really? A flexing tyre (and an under-inflated one) will deform and increase rolling resistance,
that's why we pump them up so hard. Any extra, or stiffer sidewall material would add
to stiffness and decrease RR.
With a tyre as small as a bicycle tyre, the deformation wouldn't be that great, so
you'd still get some braking, and with a flat, you wouldn't want to slam the brakes
full-on anyway. And given the choice between a flat tyre and a rim failure,
I know which one I'd choose. That's the point of the idea, moving the wear from
braking from an expensive, infrequently-replaced component to a less expensive
frequently-replaced one.
Actually this is not correct. Bias belted tires on cars of days gone by had stiff sidewalls, then radial tires were invented with thinner sidewalls and radial direction plies allowed the tire and sidewalls to flex increasing handling and decreasing rolling resistance. Bicycle tires do the same thing which is why you see paper thin sidewalls in tires like the Conti Supersonics, sure they run high psi but that psi is the same for thicker sidewall tires too! The thinner sidewall allows better handling and lower rolling resistance. However as sidewalls get thinner damage to the sidewall goes up so one has to be careful that they buy a tire like the Supersonics only to find them tearing within 500 miles of street use.
You are right about underinflated tire though, and an over inflated tire will lose traction plus increase rolling resistance on rougher surfaces.