Originally Posted by meanwhile

There's an excellent wikipedia article - I already sent the link to Mr Fantasy Physcis - on bicycle performance here:

Originally Posted by cyccommute

By all means go look at the links but before you do, look at this article on bicycle drag. It clearly shows how little importance rolling resistance of the tires has on the over all drag on a bicycle. The whole discussion above has been about how to reduce a tiny fraction of drag. The whole discussion is mostly a tempest in a teapot and, in reality, has only an marginal effect for the commuting cyclist. Reducing rolling resistance is important at a professional level where tenths of a second make a difference but for the bicycle commuter, rolling resistance makes little difference.

Weight, on the other hand, can make a huge difference for a bicycle commuter. We are constantly slowing, stopping, starting and accelerating. Adding more weight to the wheels of the bicycle means that we have to put more energy into riding to get back up to speed and then, once at speed, we have to keep putting more energy into the system to keep it at speed due to air resistance which is a power curve vs a linear curve for rolling resistance. Going to heavier, wider tires may give a cushy ride but you have to pay a penalty for it.