A few weeks ago I took my 940 in to the automotive department of a local store in a major chain ("Where America Shops") to have a pair of tires installed. I specified that they rotate the tires front to back, and install the new tires on the front.

Over the weekend I had an occasion to remove one of the wheels, and noticed that the lug nuts were installed backward - i.e., the tapered end of the nuts were outward instead of inward. The lug nuts on the remaining three wheels were also installed backward.

I always assumed that the taper in a lug nut was designed to match the taper of the hole in the wheel so that tightening the nut would ensure that the hole was seated in the exact center. So my question is: was it possible that one or more of my wheels was off center due to this error? I wonder how much this could have contributed to vibration and/or abnormal tire wear?

I'd love to be armed with definitive data so I could go back there one last time and tear somebody a express my thoughts about their competency.