It measured 2 7/8" which comes out to 50.8 mm but you are right it seems kinda small. The bike is a 21 or 22" bike, so I guess I am measuring wrong.

I really appreciate the time you are taking. Even since I have swapped the other cranks i still would like to have the correct set on the bike. Once I get the correct size I will swap them back. I am trying to get a bike together so I can ride w/ my son on the weekends. My road bike wont cut the dirt trails he wants to ride lol.

Thanks so much again!!