Originally Posted by
Kevindale
I think the results from using full disks on the rear wheels shows how useful that can be. But you're probably right about the seat stays, though the more they can help shape that trailing air flow over the rear wheel, the better.
Some time ago, there was a post on TdF average speeds from the inception of the race to recent results. A few things give incremental jumps (like index shifting) to the overall trend of faster speeds, but it is really hard to tell what the gains should be attributed to. Certainly, if you took a bike from 40 years ago (say Campag SR 12 speed with round tubes) and tried to race it against a modern bike (say 2x11 speed with aero tubes), it gives an overall slower time. That said, those teams are trying to save fractions of seconds in many cases, so if there were a better design, they would use it.