Originally Posted by
Sangetsu
Racing associations didn't adopt the 700c standard because it was inefficient, or made the bikes slower. It has more or less boiled down to be the optimum size for racing. And a standard was needed so spares could easily be supplied. But group rides have no wheel size restrictions, you are welcome to see how your 20" bike fares against the big boys. If anyone else here has tried it, it would be interesting to hear your experiences.
If true, then there would be no reason for UCI to make small wheels illegal. No one would use them.
I've used both. It's hard to control for all of the factors -- my NWT is a touring bike and at least 5 pounds heavier -- but my club and training ride times were remarkably close.