Originally Posted by
Hermes
I am 6’ tall with long arms 74” wing span and legs 34 inch inseam. ERO wanted me to try 155 cranks. It is all about aero and breathing. Shorter cranks in pursuit allow a greater hip angle and sometimes are faster. I use 172.5 on TT and road and quite frankly do not notice any difference going from 165 to 172.5. I will say that the shorter cranks are probably better for my back due to putting less stress on it in lower aero positions.
In the “old days”, pursuiters used long cranks and big gears spinning more slowly with the idea that more torque generated more speed. Today, we have tweaked that thinking with shorter cranks for better body position but back to big gears.
I expected to be told to go to 165s, given all the current trends. But my fitter - also ERO - was surprised by how flexible I am and my ability to get into an aero sprint position and still turn 170s efficiently. (I am not a pursuiter, so there's that too.) Also, the longer crank arm gives a bit more leverage for turning bigger gears.