Hello Dave,
Just try “soft green soap”
applies it to the whitewalls with a soft brush; leave it for a short time on
the whitewalls. Then take some warm water and brush softly, and then rinse off
and they should look like new.
In Holland soft green soap was used in the old days, and has no aggressive
additives.
This is a cheap replacement for products
like Westleys.
Regards, Dirk.