wheel selection
I would spend some time on the A6 forum and see what people have done. You can go to the Tire Rack as they have plenty of wheels and a website that shows you what those wheels look like on your car.
If you have not purchased winter tires and wheels for your car - I urge you to do so soon before the tires supply diminishes.
The mass goes up
Your acceleration goes down
ride gets worse
Tire cannto protect the wheel, so wheels get bent, and then vibrate
and the list goes on.
Frankly, on my S6 ( S mind you) I went from factory 17s to 16s. very wide light 16s.
now most feel i'm a bit retro. or a lot retro, but certainly 17s are about the largest you really want. After that you gain weight, and risk damage. Plus the ride sux.
The ideal 17" wheel is 17" x 8" x -35mm offset; 5 x 112; 14mm bolts.
But if you really want them, remember these important words: D=2*r; R=wheel/2+width*aspect ratio ( remember to convert millimeters to inches!); C= 2*pi*r. The rest is up to Mr. Excel.
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