I note that years ago, most bikes, even in the mid sizes seemed to come with 170 cranks. 172.5, 165, and 175 were also sold, but you could more or less count on your bike and your buddy's having the 170's. Now, most mid size bikes come with 172.5's. Recently I was told that guys like Eugene Sloane might actually have been in error in his definitive books. He had long discussions of crank size as it relates to leg length, leg speed, formulas and the such which included these variables. Now I hear from a reliable source that crank size is more aptly related to foot size than leg length. Believe me, I am confused, since I always took Sloane, and S. Brown as near Gospel. (Appologies to those of the Judeo Christian faith).
Garth Libre in Miami Shores, Fl
Happily sharing my life and home with a born in Koln Germany wife,
Bianca.