Well, thanks for the cleaning tips. I had previously tried the Magic eraser, blech-white, straight bleach, baking soda, and none removed the "yellowing" parts of the ring. It was not all yellow -- just like a bleed from behind in a few areas?
Anyway, inspired by the suggestions, I went to buy 303. Local places don't carry it (they had few other 303 products though)...
So then I considered Lacquer thinner but had none laying around. However, I did find a little can of Goo-Gone. Generally good for lots of small clean-up situations. Struck me as similar to LT so I tried it. Worked pretty good!! Maybe ever-so-slightly off-white in the worse parts but overall the white walls gleamed. I topped it with some tire dressing to moisturize it some.
Thanks