When I bought my 328 several months ago, I noticed that the wheel center caps were all cracked, two rather badly. I bought a replacement set on eBay that were supposedly OEM from Italy, and aside from the fact that they were flat rather than crowned, they seemed like a good match for the originals. When I installed them (with the O-rings taken off the old caps), the only difference seemed to be that the plastic was a bit softer than the old ones, but the fit tolerances seemed similar. Well, on my first drive, I stopped along the way to get some keys duplicated, and upon leaving the car, I noticed that 2 of the new caps were missing! When I checked the other 2, one was still good and tight, but the other was very loose, so I removed it and put it in the car. (Fortunately, I still had the old set, so temporarily I put them back on, though minus 2 of the O-rings.) I should point out that at no time when outside the garage was I out of sight of the car, so the caps were not stolen, they just fell off. Considering they seemed tight enough when I put them on, what happened here? Is it possible the caps are shrinking (or the wheels expanding) in normal driving? Anyone have any bright ideas?