nasv

hey everyone... quick question, I have a size-56cm 2008 Specialized Allez Elite that fits me very well, and I'm looking at other bikes where I can choose either 165mm, 170mm, 172.5mm, or 175mm for the crank length (also interested to eventually upgrade the Allez's groupset). I'm not sure how the lengths are measured, but I was wondering if someone knew how the frame-sizes corresponded to the OEM crank-sizes for this bike (or any other way to tell.

Thanks,
-Nico

erk

Sheldon is always verbose on these topics:
https://sheldonbrown.com/cranks.html

He doesn't mention it in that article, but i'm 99% sure that they're measured from the centerline of the pedal spindle to the centerline of the bottom bracket attachment hole. I measured mine and it was dead on, 170mm.

plpete

My Allez in a 56cm size frame and my cranks are 172.5. When i upgraded them to Sram Force crank i went with the same size and everything is fine.

THEVERGE

Check on the back of the crank arms. The size should be stamped there.

Cusp

on the inner side of each crankarm (near the pedals) should be inscribed the length.

Also - go to specialized.com ... allez bikes ... and look at the geometry chart. It'll list the crank arm for each size frame.

56cm is usually 172.5mm

nasv

Thanks all... I just took a look at the crank and it says "175" on the back. Thanks to all!

fordmanvt

Don't assume you need 175 cranks, you probably couldn't tell the difference between them and a set of 172.5 cranks anyway.