I used to work at a tire shop and have delt with wheels like this.... first off try using some bead sealer on the valve stem then put it in, and go around the rim with a wire brush, some lower profile tires with hard sidewalls have a hard time seating so use bead sealer on both sides of the rim after you get it all clean with the wire brush and that should solve your problem.... if not one last thing you can try before buying a new rim would be to run a coat of bead sealant around the rim where it is welded together on the inside of the wheel. hope this helps you.