Yeah, clean them well & allow to dry. I've done them on the truck & also taken them off to get the back of the wheel coated better. Both results look good but prefer removing them. If your going to leave them on the truck, take trash bags, split them down the middle and use them to cover the brakes & suspension. Coat the tires in heavy tire shine to help with over spray on the tires. After you've done a couple coats, put the truck in neutral & let it roll about halfway around so you get better coverage on the other side of the wheel. If you remove the wheel start on the back side with 2-3 coats then flip over & do 4-5 coats on the front. Use index cards around the wheel to cover over spray. (attached pic so you see what I mean). Figure about 1.5 cans per wheel to get a really good coat on them.
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