Chalo wrote:
jeffreybike wrote:

Is there any real difference between 23mm and 25mm tires as far as
speed. Will 2mm make you that slower or faster?

There is no significant difference in speed between those two sizes of
tire. Too narrow a tire will slow you down quite a lot when you get a
pinch flat and have to stop and repair it.

The rider will never get a pinch flat if it can be inflated highly enough to
support his weight when the tyre is slammed into potholes, etc.

Instrumented tests have shown that for tires of equal construction,
wider tires have slightly less rolling resistance at the same
pressure.

But wider tyres should not be inflated so highly to provide the same
suspension and traction, so then they are slower on the smoothest surfaces,
though faster on bumpy surfaces.

Narrower tires have slightly less aerodynamic drag.

And less weight.

While
these factors mostly offset each other, all other benefits (rim
protection, ride quality, wear life, pinch flat resistance, traction)
give the advantage to the wider tire.

Sport road bikes generally work best with the widest tire that will
fit under the brakes and between the chainstays with adequate
clearance. This is often a 28mm tire.

Often 25mm too, sometimes only 23mm.

~PB