Originally Posted by
Cfiber
Nope! Both mass and radius are important.
But that would be true, regardless as to which wheel we're talking about! All other things being equal, the larger wheel should be heavier. Therefore, it will have more weight and be harder to speed up or slow down.
What do you mean? ...Those are all facts, given the same tire width!
Lighter and more aerodynamic wheels will help you to accelerate and maintain speed, both by decreasing air friction and having less mass.
Tom Sarazac explains the wheel diameter thing best:
www.tomsarazac.com/tom/opinions/wheelsize.html
But he also seems to think that benefits from the smaller size are offset by the greater rolling resistance. And the aerodynamics argument gets complicated because a 26" wheel will have to spin faster to maintain the same road speed as 700c wheel. So while a 26" wheel has a smaller profile, the spokes need to push through the air at a faster speed.
The bigger question is of course does it even matter. I suspect tire choice makes a bigger difference than wheel size (as far as 700c vs 26" goes).
As to the 5 year old original post: "Why not 26 inch?", looking at performance aspects is the wrong approach. My guess is that the "commuter bikes" we're now seeing in the states are loosely based on city bikes from Europe many of which use 700c or the old 28" wheels.
26" wheels are popular in the states because of the commonality of the mountain bike. The original mountain bikes were more or less beach cruisers which used 26" wheels and really big tires.
So I think the reason for 700c wheels on commuter bikes is historical in nature and not necessarily because of some inherent advantage to 700c wheels for commuting. I also believe that the reason for 26" wheels on mountain bikes is historical rather than the result of careful study and testing.