Originally Posted by
Speedo
I go back and forth between bikes with 170 mm and 175 mm crank arms. The bikes are different, so I notice a difference between bikes, but I really can't feel anything different in the crank motion.
I can't tell the difference between 170's and 175's either, because they both fit me the same: too big!
Seriously, you're talking about a 3% difference in crank size. That's almost nothing. Try alternating between 180's, 170's, 155's and 140's for a while; not only will you feel a difference, but you will quickly learn which is the best size for you.