I don't know?, I have to laugh somewhat reading this thread again, and I'll say it again, every white wall or white lettered tire I've had has "browned" whether it's on the car in use, or sitting in the cellar or garage, been like this since the 60's having to clean browned white walls or white lettered tires on an occasional basis


If you want the letters bleached bright white, use Tri-Chlorethelene, on the white portion only with clean white rags