I'm sure that y'all are fully correct about the heat absorption of black radiators, fridge backs, etc, but there seems to be one thing missing from your consideration: Those surfaces are black to absorb heat energy from a fluid passing through it thereby cooling the fluid, and cooling the engine, or refrigerator. Since the rims themselves are what the OP is trying to cool, he should have silver or white rims to lessen the heat as there is no secondary fluid which he is attempting to draw heat away from.