REgulat 16" tires are OK. The inner depression Hammer and the others speak of is th e"well" - the tir ebead has to drop in that 180 degrees away from the bead that is "up-and-over-ing" the rim. The bead ID is 16", the OD of the rim is more - like 18~19 inch - something has to shift to make it work gometrically - that's where the well comes in.
As for rigging up some sort of bolt-togeher affair - could be done, but this system already works, why bother?
I do agree that with the ring seated orperly and fully in the groove in the wheel proper, and the tire bead slipped up over the ring "falt fully - the ring can go nowhere. BUT if any one is NOT "fully" or "properly" seated, or there is any significant imperfection - the thing CAN go "BOOM" - be careful, and chain the things together.
"other peoples junk, is something or other" - Militarypotts 02/07/2011