Wheel fitment dilemma

["Mike_Platt" <mplatt@aspi.net>]

I just sold my 1897 TQW this summer and my 1991 200 TQ. I have a set of
winter wheels and tires for each car. I want to mount them to a 1996 A6
quattro wagon and a 1994 S4. They bolt up fine and seem to fit. How do I
tell if I have the correct offset? Here is what I have for the S4. 8Jx16H2
ET40 stock wheels. 7Jx15H2 ET40 steel wheels from 1991 car that had UFO
brakes. The A6 has 7Jx15H2 ET45 stock wheels and 7Jx15H2 ET45 Fuchs alloys
from 1987 car. If the ET means the offset I'm hoping I'm looking good! All
the above sizes where stamped on the wheels.Does anyone know the answer?