Originally Posted by
abdon
The biggest difference would be a 650b wheelset. Long story short; the biggest impact on rolling resistance is tire pressure. It just happen that bigger tires cannot take a lot of pressure. So, you want smaller slick tires that can take higher pressure, but doing so shrinks your tires which changes your bike geometry and you have to crank faster for the same speed (which some actually like). a 650b rim is a bit larger than a 26" with the end result that even with the skinnier tire (that can take higher pressures) you end up with the same tire diameter as the fatter 26" tires. The one caveat is that your brakes need to have enough reach to contact the bigger rims.
Sorry, but I disagree completely. The skinny tires + high pressure = low rolling resistance myth has been extensively debunked which is why so many racers have moved to wider softer tires (too many sources to list, but search for Jan Heine and tire pressures). Also, over inflating your tires is only going to have an infinitesimal effect on tire pressures and will not change either your bike geometry or the gearing in any way that is detectible by the rider.