Bill,
Don't use gasoline. It destroys rubber. Don't believe me? Pour a little on your drive way, and step in it with a tennis shoe. The bottom gets gooey and sticky. Enuf said.
Bleche White is a good alternative. Softscrub is as well. Gentle scrubbing removes some of the problems, and the bleach removes others. Always rinse well.
The best alternative is to KEEP THEM CLEAN. That way you use less harsh chemicals.
I own a car wash, and often times people come in who want clean wheels and tires, but it has been MONTHS since they did anything. The brake dust builds up on the wheels, and what with that and road grime, actually corrodes today's aluminum/magnesium wheels. These are the same things which make your tires and whitewalls dirty. By then it is too late. Today's crop of wheel cleaners such as Meguires Hot Rims and Eagle One's Chrome and Wheel cleaner contain Hydroflouric acid which is arguably one of the most corrosive compounds every devised by man--they work well, but best NOT to let the wheels get so bad that you need this stuff.
Michael Salemi
1969 280SL
Signal Red w/Black Leather
Restored