Have used Bleche-Wite, Simple Green, SOS pads etc for 40 years on all types of raised white letters and white walls to great success.

The problem I mentioned, these solutions are of little value. Something else is gong on on these tires,,,,,and as mentioned in original post, Michelin is aware of it,,,as well is my local America Tire Store,,they have told me that they have warrantied swappd out several sets of TA's. Twice on my 71 Vette.

This browning is bleeding up from the tire into the lettering,,,which to coin a phrase: "Beauty is only skin deep, ugly goes to the bone". Therefore surface cleaning has little effect on the problem.

Next time at a Goodguys event, pay attention to cars with TA's. You will see what I mean. Some are as they should be, while others are not,,,,it is not merely poor detailing.