When they turn brown just break out the lacquer thinner and a rag and wipe them off. The BFG's with all their shortcomings is still the best looking tire for our cars IMHO.
Lacquer thinner won't work. The brown is from the rubber leaching through the letters. The brown is not on the surface, it is all the way through. Nothing works to make them white again once they go brown except a paint pen.
