White Letter Tires?

Another vote for Bleach White. It gets the white letters white, and removes the brown crap from the black.

I just spray it on and use a handled brush to scrub the tire clean. Keep in mind, if you let bleach white sit for too long on the tire, it will leave brown spots on the letters. Just scrub, then hose it off fast. Also, I recommend wearing gloves, this stuff is kind of nasty.