The weight-at-the-wheels is apparently the most apparent in the mountain climbs. Lots of pros had specific clauses in their contracts to use certain ultralight

The weight-at-the-wheels is apparently the most apparent in the mountain climbs. Lots of pros had specific clauses in their contracts to use certain ultralight rims regardless of the official team kit of the proteam. Anecdotally, I think this is related to the inevitable far lower rpms climbing a hill and that highlights the uneven power output as a rider (even heavily trained pros don't output perfectly distributed power as they turn a crank). At the low RPMs and variant power highlighted combined with the unending pull of gravity, I guess there's lots of micro-accelerations of the wheel rims.