Originally Posted by
cplager
Assuming you have the same make tire at the same pressure, the rolling resistance will be less for a larger width tire. The air resistance of the larger tire will be more, but at the speed of the average bicycle, it won't be a big effect.
Yeah, but then you're cheating. If you have a 23mm tire and a 50mm tire at the same pressure, either the 23 is underinflated or the 50 is overinflated. Sure you can get great rolling resistance running a 50mm tire at 120psi but the ride will be rock hard and punishing. Each size tire has a given pressure that makes sense so the rolling resistance is more or less a wash.