Originally Posted by
Bacciagalupe
I'm amused by lots of things pros do.
More to the point, pros ride slightly smaller frames to get their
bodies into a slightly more aero position. A difference in rider position will overwhelm almost any theoretical frame advantage.
By the way, the allegedly über-aero Cervelo S5 actually has a taller head tube (and a shorter fork) than many road bikes, including the R5. Care to explain?
He's been riding it in regular races as well.
While it is entirely possible he's doing it for sponsorship reasons, I can't imagine he'd ride it if he believed it would negatively influence his performance.
Cancellara may find it more comfortable/less fatiguing, especially for cruising in a peloton. But that is irrelevant to the original question.
Hypothetically, given perfect set up for a fit and flexible rider, a race geometry bike will be slightly faster than a comfort geometry bike. That doesn't mean that it's the best bike for Spartacus or the OP. It's just the answer to his actual question.