5x112 mm
The wheel offset for the Audi A6 is +35mm. Most 18 or 19" wheels designed for Audis will use that offset although there are exceptions.
The wheel spacing itself will correct, or increase, the offset and properly push the wheel out. The spacers can also be change out to provide a better spacing and offset.
Sedan Only: front 45 mm, rear 45 mm (sport 50mm).
45mm on the SEDAN ..This is for a 17 x 7 inch. Rim. 35mm on the COUPE .. This is a good offset for this car seeing as the rear Rim is 8" wide, and the fronts are 7.5"
34-45 offset
Back spacing is a wheel term. It is the back spacing of the wheel, to allow a larger tire to fit in the wheel well. It is built into the rim, so you have to order them with the proper backspacing, or officially called negative offset. A tire and wheel shop will have a tool that they can bolt onto your car, to determine maximun allowable offset, when ordering wheels.
Is the estimated tuck in or out from the center of the wheel, example: (nissan sentra) 18x7.5 +40 offset is tucking in 40 mm from the center of the wheel or (old chevy pickup) 15x7.0 -10 offset is sticking out 10 mm from the center of the wheel.
The stock wheel has a 55 mm positive offset. Positive offset means that the wheel is tucked into the fender well 55mm more than it would be if the bolt flange of the wheel were perfectly centered in the wheel. Negative offset means that the wheel will stick out of the fender well more. So........ If you reduce (55mm-45mm) the positive offset my 10mm, your wheels and tires will stick out of your fenderwells 10mm further than the stock wheel, assuming that the aftermarket wheel is the same width as the stock wheel.
+45 offset
+45mm offset (6.25" B/S)
11 mm 5 point offset closed in wrench
2008 Honda civic steel 16" wheel 45mm offset