Pete,

Okay, there's your problem right there... those are the older style Jaco rims. THere's nothing wrong with them, but if you look at the center hole, you'll see some ridges inside there. Those rims are meant to be used with un-flanged ball bearings. The ridges in the hole are there to keep the unflanged bearings in place. You are probably using flanged bearings, which won't sit deep enough in those rims, and that's why you cant get the nuts on the axles properly.

You can solve the problem by using unflanged bearings in those rims, or you can buy some rims that are made for flanged bearings.

If you can't easily find some unflanged bearings (the size you want is 1/8" x 5/16") PM me your address, I have a set I can mail to you. All the rims I have now use flanged bearings, so I'll not be likely to ever use these unflanged ones.