I use the Eagle Wheel and Tire cleaner and a plastic bristle sidewall brush from Wal-Mart. The Eagle cleaner works great on the brake dust and it is safe for the clear coat on the factory aluminum wheels. Saves me from having to buy an additional wheel cleaning product.

 

When I had the white letters out I never had a problem with them deteriorating. Sprinkled the comet on the wet brush and went to town. Worked like a charm.

 

I have been using it on my goodyears on my camaro for the past 7 years and they still look the same. I cant vouch for every tire and every type of lettering but from what ive seen on all my white letter tires ive owned i never saw the comet deteriorate the lettering. It might over a long long time but, but youll probably have to get new tires before that would happen.