Do not purchase these tires if you are running on an Audi Sport suspension on an A4 with the alignment set to S4 specs.  The tires were excellent for one summer.  I had no complaints, even on the track. After 12,000 miles however, the tires began to howl at highway speeds.
The outside of the tread cupped/feathered.  My Audi Certified Mechanic said that the sidewalls are too stiff for daily driving.  He said that he has seen the same problem with these tires on an A6.  I searched the web and found other A4 owners who had this problem with the same mileage.  These tires may be less expensive, but $500+ is a lot for a single summer of enjoyment