Re: BFG Raised Yellowing Letters @^#!
I had the same problem with some BFG's several years ago. No scrubs or cleaners worked so ultimately I bought a white paint tire marking pen and colored over the yellowed letters. Kind of a pain, but they looked good again. Check the manufacture date on your tires, they may need to be replaced if so old the letters are yellowing. I ultimately replaced mine due to age and not wear.
'69 Z/28, Lemans Blue/White Stripes, DZ302, Tremec Magnum, 4.10, Procar Elite Seats,
Custom Upholstery, Dynatech headers, 17" VWW V45's, 235/45, 275/40, C5 Front Brakes