Train in Spain said:
A good question, if you find out the answer I'm sure Andy would be pleased to hear.
Actually, I don't think he's going to like my answer, 'cause there isn't much he can do about it.
I think someone almost nailed it earlier: weight. I don't care what the official weights are, there's no way in hell Schleck is 68 kg. I've ridden right next to the guy and he's 60-62 kg, max. That makes him roughly the same weight as Contador, but 3 inches taller.
Obviously, these guys are putting out almost identical w/kg, but with Contador being shorter/stockier, his w/cda is higher. While Contador may be able to hit a higher percentage of his full power output on his TT bike (trains on it more maybe, or maybe can just pedal more bent over then AS, can focus more in a solo effort), Schleck is going to have a really difficult time ever reducing his drag to AC's levels, given his size.
There have been a ton of good TT guys who are light, some of the best: Hinault, LeMond, Rominger, so it's not fair to automatically pull the doping card. They're all compact guys though. 6'1" and lanky is a tough build for TT's. I don't doubt he'll get a little better, but his position is already pretty good. I don't see him ever being able to match Contador in the TT department.