I just bought a 52cm road bike, and took it home without checking out the length of the cranks. All my life I've ridden a 50cm bike with 170mm cranks. I grudgingly upped to the 52cm frame, (was told by the tech and my 11cm stem that my old bike is too small) but was surprised to see 172.5mm cranks on it. Is this right for a 52cm frame? Does 2.5mm really make much of a difference? I'm hoping someone has insight to this as I really want to ride my new bike!!