This may not make any sense, but I'll ask it anyway.
I have two road bikes. One for long distances, and one for short training rides. The geometry is quite different between the two, but the components are similar. Both bikes have a 53x39 crankset, but the training bike has a 12-25 cassette, while the distance bike has a 12-27. The training bike is also around 3 lbs heavier.
So, the training bike should be tougher on hills, right? Nope.
I rode both bikes back-to-back on the same ride. The ride has one significant hill, and I've noticed on the training bike I can attack it in a 39x23 with no problems. Mixed standing and sitting. When I reach LT, my legs have a slight, even burning that's distributed evenly between my quads and hamstrings.
When I take this same hill on my distance bike, at LT I get an intense burn that's concentrated in my quads only, even if I drop down to a 39x25. At the top of the hill, I'm far more spent than on the traning bike, and I take longer to recover.
My only logical answer for this has been bike fit. The seat tube angle of the training bike is more slack than that of the distance bike, so it positions me farther back. The top tube length is also a bit shorter (both bikes have the same stem length) and the bars are a bit higher in relation to the seat.
The question then is, can a 1/2 degree difference in seat tube angle (assuming I'm remembering my OCLV's geometry correctly) make this much of a difference? Does anyone else have any other ideas on this?