I prefer the sanding method because chemical processes do not allow for error. The purpose is to make the white/letters appear to be new AND untouched. If the black sidewall area surrounding the letters becomes damaged, altered or manipulated looking, it ruins the desired appearance.
Below are before and after photos. If the letters have deep cracks or dry rot, you can use 400 grit wet or dry sandpaper to remove the old surface. The finish of the rubber will still look new and smooth, even while using the 400 grit paper. A raised white letter or whitewall tire has a solid white layer of rubber beneath the thin black veneering of rubber that covers the sidewall. The letters are solid white blocks that allows for the old oxidized/cracked surface to be safely removed. After using the sandpaper, the white surface residue can be cleaned off with lacquer thinner. I stretch a piece of cloth over my finger, dip it in the lacquer thinner and wipe across the face of the lettering. It leaves them as white as they were when new. Keep in mind that there is no paint or fake coating that is left on the surface to rub or flake off. The rubber that remains is completely original and should last for years with proper care!
