How do I tell what my axle size is on my mountain bike? What do I measure on the fork or wheel to tell?Do you measure the skewer?
If you don't specifically know then it is likely a 3/8 axle. There are bigger ones for through axle and others but I bet it is just standard. The big-uns are on higher end bikes that are TRUE mountain, AM, DJ, or DH bikes. Skewer diameter has little bearing on the axle diameter.
Just google your bikes model and everything will be there.