77cm inseam, 170mm cranks.
Originally Posted by
prendrefeu
Well, there's a reason for that. The banked slopes of a track mean that there is even less distance between the lowest point of the pedal/crank and the surface you're riding on. With a bicycle that has a direct drive with NO freewheel and NO brakes, you don't want to be clipping your pedal stroke on the track surface (unless you really like being jolted from the bike like riding a bull at a rodeo). Hence, track cranks usually come in 165mm or 170 standard, with 165 being the overwhelming majority of the production run.
OFF the track, the track racers tend to stay with the same crank length on ALL their bicycles, regardless of what type, because their bodies (knees, muscles, legs) have become accustomed to the motion associated with that smaller cyclical radius.
The shorter cranks are also desirable for spinning since you have to use the same gear at all speeds.
I'm not sure if you're correct on the same size on their road bikes. When I raced track, I still used 165 on the track, 170 on the road, and 175 on the mountainbike. My body was fine with all of them. I could spin more easily on the track and climb better on the mountainbike.