I've been following this thread with amusement. It's very likely we'll never really "know" what is the reason. The more I read the more I look at the rider and not the bike. At first I thought of rider positioning, then gearing (although I would think the rider would already have considered this, but...), I never really though that tire pressure or brake rub would be involved (again believing that the rider would have considered this but then his post #13 suggests at first he didn't...). So I find myself going back to the rider and his perception being involved. The only mechanical not yet discussed is crank arm length. Go for it guys Andy.