Originally Posted by
tungsten
Really? So someone 5'2" should be riding 177.5's?
I've had knee issues long ago due to overuse and not stretching and more recently job related imobility stuff but going into retirement and now having the time to ride every day I figure anything I can do to minimize wear and tear on body is a no brainer.
No.
No matter what the height or inseam a person has, they should ride the crank length that gives them what they want.
I'd be on 174.5 mm cranks in your formula. Several years ago I tried to run 170 mm cranks but had an annoyance behind the back side of my knee. Tried real hard to like them for 4 full months but finally swapped back to the 165 mm cranks I seem to do best on. Every time I get on a bike with longer cranks I feel like I'm thrashing about and get tired quickly if nothing else.
I've got a 87.6 cm inseam.
At best, formulas for crank length might tell you the most length you should consider. But not what you should get or start at.
5' 2" with a 90 cm inseam? Wow.