Are these larger or smaller than 15" rims and by how much? Is it possible to machine them smaller in the tire groove to act as bead locks?

The problem with them is the cost of the tires to put on them.

are you asking if it'd be possible to machine 390mm rims to use a 14 or 15" tire? if that is in fact what you're asking, i don't know the answer, but maybe this will help clarify the issue?

390s are aproximately 15 1/4 inches

 

Dunno about machining them though.

if you took off a 1/8" all around the groove where the bead sets, and 1/8" all around the outside edge (rim) on both sides, a 15" tire should in theory fit then. not sure if taking 1/8" off the groove would affect the stability of the wheel or not.

 

wouldn't really help much as far as acting like a beadlock though. don't think that 1/8" extra lip is gonna stop much if your aired down enough to need bead locks. or if you're cornering fast enough to need bead locks.

I've thought about cutting some down to 15" but haven't got a chance to spec them out yet (somebody wanna give me a set ). It's really a question of there being enough material left to be safe. My new lathe should be here soon... anybody feeling like a Guinea pig?

 

Gary

I was thinking of doing that for the last few years cause that would give us another option and yeah they are approx. 15 1/4 inches so just taking off the extra material would make it to fit 15 inch tires on and just remember to do all the champhers and stuff so it seats correctly

Yes, that is what I was thinking. Possibly notching the inner bead seat to fit 15" and maybe cutting and drilling the outside for a 15" bead locker ring.