My +8 had something very similar, much more annoying then it sounds on paper, as you spend all your time trying to drive around the noise. It ended up being shipped back to the factory, after trying a lot of things and having the car for a couple of months, they checked the wheels "two were just on spec and one was outside spec". Unfortunately I was never able to find out what "spec" was.
The MMC changed all 5 wheels from the "Indian" Chrome Wire Wheels to the then newly introduced SS ones, which I was impressed with.
The problem has never reappeared.
