I'm planning on servicing the hubs on my winter wheelset (basic Bontragers with cup and cone bearings) and based on the weather they've ridden through lately I think its probably a good idea I replace the bearings rather than just repacking them.

My question is, does anyone know what size the bearings in the hubs are likely to be, or is there any way I can find out so I can have some new ones ready for when I can find time to do the work?

Thanks in advance!