Originally Posted by
foamy
I'm not an authority, but what folks have been saying is basicly true. 26 in. for anything out of the States or off roading, 700c for paved roads. That's been my experience. If you're gonna be riding the roads, the larger wheels are faster. That may or may not make a difference to you.
Sorry, I just don't think there's any evidence that would demonstrate that 700c wheels are "faster" in the real world.
However, typically bikes with 26-inch wheels are set up with big, fat, heavier tires, mounted on pretty sturdy rims - so they are often heavier than the 700c bikes they are compared with (which typically have narrower, lighter tires). But one can obviously put pretty narrow tires on a 26-inch wheel and conversely mount fatties on a 700c wheel (assuming that the bike in question would accept those tires).
It is true that a 26-inch wheel would travel less far with each revolution of the crank, but that can easily be corrected by a change in gearing. It's also true that a Bike Friday with 20-inch wheels is plenty fast, too, given the right gearing.
But - all other things being equal - a 26-inch wheel would not necessarily make a bicycle slower than a 700c wheel.
Happy to stand corrected if there is evidence to the contrary.