A. Shea

Just a thought...

Has anyone thought of putting HP2 calipers on a C6? I am assuming that the clamping force of the HP2 calipers has to be more than the clamping force of our stock calipers. (Yeah, yeah, I know what happens when you assume They might even bolt right up. It would give us a much better pad and ss brake line selection. Any thoughts? TIA.

gk1

IMHO the clamping force of the stock caliper far exceeds what anyone would normally use street driving. Now if you are going for the track what you really want is repeatably consistent stopping which can really only be achieved through a larger brake rotor or complete BBK. AFAIK the stock C6 caliper is similar if not identical to the B6/B7 S4 caliper which Audi determined to be of superior design and performance than the HP2 setup of the B5 S4 era. IMHO if I were going to go through the hassle of replacing the calipers I'd just go for the entire BBK...it's expensive, but at least then you know for sure the rotor is larger (floating rotor) and the BBK caliper is stiffer, lighter, and certainly does have more clamping force and the whole system then can take the rigors of track driving.

A. Shea

Can't disagree with the logic, but... I was thinking of the idea because I have all the parts laying aroung the garage, and there are a number of floating rotors that can be purchased for the B5 S4 that would/should fit with the proper caliper carriers.

gk1

I see. If you already have the HP2 parts that certainly does help the cost aspect, but I still think if you are going to find caliper carriers that accommodate larger rotors with the HP2 you may still be better served by finding carriers that allow for larger floating rotors and retaining the stock caliper. (Maybe S6 carriers fit?)

Also keep in mind the HP2 was in use on the lighter B5 S4 and C5 A6. It likely will not be a significant difference, but I do not know for sure.

For referenc:
B5 S4 spec weight 3600-3700 lbs.
C5 A6 2.7T 3950 lbs.
C6 A6 3.2 4034 lbs.
B7 S4 tip 3990 lbs.

A. Shea

The weight difference would not be a worry as the HP2s were also used on the Allroad 4.2 which had a curb wieght of 4277 lbs.

One of the reason Audi stopped using the HP2 calipers was because they were so good, they had a habit of warping rotors (a floating caliper would fix this problem). I remember seeing a comparison a while back of the HP2 vs. the Boxster calipers and they were virtually identical.

One of my other thoughts was that the HP2 calipers would allow a hugh range of pad choices, and they can be swapped in a mater of minutes.

BTW, I greatly appreciate your thoughts on this.

gk1

Ah. I didn't know they were used on the allroad 4.2. That is a pretty heavy beast.

I'd be shocked if they stopped using them because they were "too good". I mean they were OK. I'd sooner believe "cheaper to manufacture" would be reason enough for them to switch to the current single piston design. Warped rotors would have more to do with too small a rotor on too heavy a vehicle. Which perhaps was the problem with the allroad.