2013 A6 prestige - Wheel sizes?
 

Does anyone know what size of wheels will fit this car, 2013 A6 prestige? I have not been able to get an answer from multiple Audi dealers with them checking my vin. I was told an 18 inch wheel should fit the car but, that a 19 inch would be required if I had the $20,000 something ceramic brakes, which I do not. Any help on the sizing would be greatly appreciated!

The car currently has stock 20 inch wheels and summer tires but, I want to get some winter tires. Also there are not a lot of options for 20 inch winter tires so I thought I would go for 18 inch wheels, the same size that would have been on the car originally without the 20 inch wheel option. The car does not have the sport package, just the standalone 20 inch wheel option for that year. After a lengthily search, contacting Audi dealers and server wheel manufactures I was told that the following 18 inch size of wheel would fit:

18x8
5x112
offset 45

I ordered some Konig Oversteer Wheels in this size and the wheels did not fit to my disappointment, even though that site I order them from confirmed that wheel should fit the make and model. The wheel will not sit flush on the hub. The wheels will not clear the brake caliper. Any help with the correct wheel sizes for this car would be greatly appreciated.