Quote Originally Posted by arielmoon View Post
Does it say somewhere on the crank? It is not listed in the specs on the trek site.
On my 105 cranks it's stamped on the inside of the right crankarm just above the pedal.

I don't know whether there are any good rules for choosing crankarm length. Maybe Knott or someone can weigh in? One of these days I'm going to pick up Andy Pruitt's book It's not just your leg length, it's the tibia/femur ratio (which can't be measured very accurately without X-rays), but a fitter should be able to check your knee angles at both the top AND the bottom of the stroke.