Originally Posted by pharnabazos
The smaller the wheel the 'faster' it is, because of less rotating mass and less aerodynamic drag.
this school of thought was why 650 wheels were big in triathlon for a while. However it's not confirmed in wind tunnel testing. While the smaller wheel presents a smaller profile to the wind, it has to rotate more times at a higher speed, for any given bike speed. Thus increasing the drag from the spokes, or the "egg beater" effect. The studies I've seen indicate its about a wash.