Another trick you can try, befor you drill the holes for the screws, take a long zip-tye and fasten it all the way around the tire and pull it up tight. This will seat the tire all the way down into the rim for when you drill it.

I have to disagree with Eddie, do use the screws. A freind of mine started to complain about his brakes not working, when we looking into it the tires were spinning on the rims very freely. They had lapped them selves in with time.

Steven