[ApriliaGuy]

Had it happen on my wife's Subaru. I had one that would go down a few pounds fairly quickly, so I mentioned it when getting new tires. The tire shop guy said he sees it all the time. He used a wire wheel on a grinder to clean 'em up and then brushed on a black colored goo that the tire guy said was similar to "Plasti Dip " (the stuff for tool handles). That was 3 years ago (on an '03) and no problems since....so far so good.

 

[ApriliaGuy]

I have no Idea how it may effect balance. I know a small variation in paint thickness is no biggie. But Plastic may be another story ..

Yeah. In my case it was just a bit, done with a foam brush to the bead area only. Doing the whole inside of the rim might cause a bit more trouble.