S4 Wheel & Brake

December 19, 1999

A Word About Audi's Advanced Brakes
Courtesy of Audi of America

Many AudiWorld readers have called into question initial information that was provided by Audi regarding the front brakes on the new S4, A6 2.7T and A6 4.2. Audi originally had indicated that the HP-2 brake was a four piston design. This information was printed in early press guides for the car, as well as on some of the invoices for the actual cars. Once deliveries began in the U.S. it quickly became apparent that the design did not utilize four pistons, but rather only two.

Official Audi Statement on Advanced Brakes:

There was a small error in some very early 2000 model year documents which described the design of Audi's advanced HP-2 front braking system. The HP-2 front braking system is standard on the models below (the dimensions of the discs are in parentheses):

  • 2000 Audi S4 (321 x 30 mm discs)
  • 2000 Audi A6 2.7T (321 x 30 mm discs)
  • 2000 Audi A6 4.2 (321 x 30 mm discs)
  • 2000 Audi A8 (as of calendar week 45/1999 production) (323 x 30 mm discs)

    It was mistakenly stated in a small number of places that the HP-2 is a "four-piston" brake. This error resulted from confusion arising from the fact that, indeed, the previous HP-2 brake was a four-piston design. The new HP-2 high performance braking system for the models shown above is a four-pad design, but it has two pistons.

    The newer design has several advancements. It is made of aluminum, which enables it to be lighter, saving nearly five pounds of unsprung weight at the front of the car. Because it is larger than the previous brake, it enhances braking efficiency while increasing its effectiveness. This revised brake is a floating caliper design, which has two live pistons, instead of four. However, its braking performance actually is even better than the already excellent performance of its four-piston predecessor. The brakes include four individual pads and have the same swept area as the previous brake.

    We apologize for any possible confusion. We appreciate your enthusiasm for Audi and invite you to enjoy the rest of our newly redesigned Web site.

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