Both Steve S and I have put Porterfield R4 pads, I think a few others have tried their R4S compound as well. There are really no other aftermarket pads available right now for the S4 calipers (though I hear we should be seeing Hawke and Pagid come out with pads soon).

As for performance, they're a good improvement from the stock pads on the track. Not as good as a proper big brake set up (ala Alcon), but they are my intermin solution.

If you want to run them on the street, be prepared for getting a lot of attention: they are incredibly LOUD. Squeeks, squeals, moans -- louder than you can expect.<p>Sharon
'00 S4

http://registry.audiworld.com/audi/registry/details.asp?car=4559

I tried to get by with the race pads for the three weeks before Lime Rock and couldn't stand it after 4 days. Swapped back to my Mintex pads for the street.

Heard they are great on the track once they are warm, though.

Jon