The best product I've found to clean whitewalls and keep them clean is Westley's Bleche-White. It's made by Black Magic now.

Contrary to popular belief, it does not contain bleach. Wash the tire, apply the product and scrub with a scrub brush. Don't use bleach on whitewalls or, just like your socks and underwear, it will turn them yellow.

I've been using it for over 20 years.

1950 Chevrolet 3100 (Ol' Roy)

1939 Packard Standard Eight Coupe (The Phantom) | 1956 Cadillac Coupe de Ville (The Bismarck) | 1964 Ford Galaxie 500 coupe |1966 Ford Mustang (Little Red) | 1969 Pontiac GTO (The Dishpit) I 1979 Ford F-100 | 1976 Ford F-150 (Big Red) | 1995 Ford F-150 (Newt)