Originally Posted by T.REX63
I'm slow today, forgive me
(still suffering jet-lag). What could be achieved by pinching the two beads together, while on the rim...?
And, yes, you're absolutely correct, that method would keep the beads in the center of the rim. But, then what...?
If you've tried mounting tires, you know that when going from tire completely off rim to completely on rim, the first bead goes on relatively easy. You probably don't need levers with most tires. Getting the second bead on is harder because you are twisting the tire to keep one side of the second bead in the middle of the rim while you lever the other side over the rim. With the tire completely off the rim, strap the beads together and the whole tire should be as easy as the first bead to get on the rim.
Mind you, I have not tried this so it's strictly theoretical to me at this point but it sounds good.
Once it's on the rim, you don't need to pinch the beads together. The whole thing is about making it easier to get the tire on the rim.