Originally Posted by
hokiefyd
3/16" sounds right for front hub bearings. I think the rear hub bearings are typically 1/4".
I saw your post minutes before I went to write up a post about the common sizes - you couldn't have timed it better!
I'll write up a quick table for other novices like myself who come across this post
Front hubs*: 3/16" (4.76mm) -- 10x per side (20 total)
Rear hubs: 1/4" (6.35mm) -- 9x per side (18 total)
Cup-and-cone bottom brackets: 1/4" (6.35mm) -- 11x per side (22 total)
Front steerer: 5/32" (3.97mm) -- count varies (as far as I am aware)
Pedals: 5/32" (3.97mm) -- count varies (as far as I am aware)
*Rarely, some front Hubs, such as the Campagnolo Record, Nuovo Record, and Super Record, as well as some other random exotic hubs usee 7/32" (5.56mm) bearings.