Just put 15mm wheel spacers on the rear of my e92 and have noticible vibes at 80mph+. Everything was cleaned up nicely with a wire brush prior to install. I ran them for 3 days and finally got a chance to pull them off last night.
The spacer fit very snug onto the car's hub the problem is the interface with the rim. The spacers's hub centric ring is undersized to the rim, with the spacer placed in the rim you can move it back and forth by about ~.020". This is enough to offcenter the rim and cause vibration.
Anyone want to buy some 15mm spacers with 37 miles on them? just keep it under 80mph...
