Need a little help. Just replaced my SportContis' with Potenza 730's. When they balanced the wheel and took off the old weights it (they) left black adhesive on the rim (where the old weight was). Am afraid to try a single edge blade for fear of scratching the wheel. Anyone have any thoughts as how to get the crap off. Called my tire man in Santa Monica, and he was no help. Thks. for any info.