Originally Posted by
PeteHski
Rim-brake specific wheel rims are in fact heavier for obvious reasons, but the hubs are lighter. Overall wheel weight is usually within a few grams. Lighter wheel rims are more efficient, so that's a win for disc-specific wheels.
? Actually rim-brake specific wheels are easily 100 grams lighter. Compare the specs for Campagnolo/Fulcrum wheels, which has about the best engineering/QC control of anyone, and rim and disc-brake versions for each of their popular wheel lines. As far as the rims (just the rims) for disc wheels being lighter, I don't see it. A big rim maker such as Alex, who makes rims for several wheel companies, seems to make alu rims about the same weights for both. Alu rims bottom out at about 400g, with no weight discount for disc-specific versions.
Theoretically, I could see how clincher rims would need to be bulked up for rim brakes, due to the compressive forces applied to the braking surfaces. Particularly when you factor in rim wear. However, since all high-level competitive riding is done on tubulars (past, present and forever), and since rim braking forces on tubular rims do not crush the clincher rim hooks, compressive brake forces here are nearly not as much of a problem. BTW: the inherent and insurmountable advantage of tubular rims will save you another 200 grams per wheelset. Check the published specs.
BTW: rims take years if not decades to wear, an overstated benefit of discs. When they do wear out, it takes about an hour and a couple of beers to transfer a new rim over to the old hub/spokes including truing/tensioning.