I've been having some vibrations after having my tires rotated. In fact, the car was never quite "right" after having aftermarket rims installed. It turns out, the plastic rings included with my wheels were not a good fit for an Audi A4 Quattro. Looking at the hub, the locating diameter is a thin surface 2mm about 5mm from the locating surface. The rest of the hub is undercut. The plastic rings supplied sat in that 5mm space never touching the 57.1mm diameter so the rings were effectively doing nothing.

My advice is stay away from plastic rings and get metal ones that have enough reach into the bore to correctly center on that 57.1mm diameter. In fact, I used Loctite to attach them to the wheel rim. I made these changes on the advice of my local Audi dealer. Audis are very fussy about Hub-Centric location.