Originally Posted by AnthonyG
The important measurement to consider is your inside leg measurement. See,
http://www.cranklength.info/ and check the crank length calculator. If 170/172.5 is about right for you sa small difference wont be detrimental. If you realy should have a shorter crank and your going longer then this wont be benificial.
Regards, AnthonyG
Yeah the femur length matters because the femur/tibia ratio affects how much the knee bends at the top of the stroke and the hip angle.
But you still need to understand guys with "short" 28" inseams are getting away with using "long" 170mm cranks becasue the small size frames use crazy 76 degree seat tube angles, etc which moves the seat massively forward and consequently lets them place their seat high enough so they don't have knee problems.