Originally Posted by sillygolem

FYI:

One piece cranks used on old American bikes (Schwinn, Columbia, etc.) and new department store bikes use 1/2" thread pedals. These are easy to recognize because they don't have dust caps or bolts at the centers of the crank arms.

Three piece cranks used on everything else use 9/16" thread pedals. You could swap some carbon fiber clipless pedals on a new racing bike with a set from a fifty year-old Raleigh if you wanted to.