A8/S8 Rear Calipers?
04-08-2002, 06:06 AM
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A8/S8 Rear Calipers?
Anyone know where I can find a new set of S8 Rear calipers? I am looking into upgrading all my brakes to Stasis Engineering Street Sport package front and rear. But I don't think rear calipers are included. I have looked all over for replacement rear calipers for A8/S8 with no luck. Are they the same as S4 rear calipers?
I have a 97 A8 Quattro, by the way. Thanks.
I have a 97 A8 Quattro, by the way. Thanks.
04-08-2002, 01:18 PM
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Re: A8 rear brake upgrade ...
.
Mike,
Since you're going to Stasis, I assume you'll be installing Alcon's -- congratulations, they make great brakes (and of course, so does AP and Brembo).
I'm not really familiar with the '97 A8 brake setup. Do you have the 312x25mm vented rotors in the front, and 245x10mm solid rotors in the rear?
Assuming the above and that Stasis package is a 4-pot Alcon with a 13" rotor -- You probably do not need to upgrade the rear calipers. Even with the stock brakes, for a SINGLE max effort braking stop from high speed, the tires are normally the weak link; and this is confirmed by the fact that ABS should activate to prevent the brakes from locking up. Under these hard braking conditions, 80+% of the car's weight is transferred to the front of the car, and the rear brakes do <20% of the work. If you add wider and/or stickier tires, you can brake even better, the rear to front weight transfer is even larger, and the rear brakes have even less work to do. StopTech has a good "whitepaper" on this subject on their web site (see link).
The only caveat might be if you take you A8 to the track. This is obviously where you'll get the most benefit from the Alcon's; your front brakes just won't fade with repeated hard braking. Under these conditions, though, I'm not as sure about your rear brakes. With the small solid rotors, cooling air flow is minimal, the pads may overheat, and your rear brakes may fade. This isn't a disaster (you're losing <20% of your braking), but it'll be a major nuisance. I'd recommend that at the track you use a high performance racing pad in the rear with the stock calipers, perhaps something like the Pagid RS 4-4 orange. With the solid rotors, though, you may overheat even the Pagid's; but only at that point would I consider upgrading the rear brakes. I'm not sure that I totally trust the specs shown in the AudiWorld models guide, but it says that the '02 A8 has the 245x10mm rear rotor, but vented. If this is true, an excellent rear upgrade may just be to the '02 A8 vented rear rotor.
Last but not least, I've talked at length with Paul Lambert at Stasis about S8 issues. Give him a call; he is very knowledgeable, and I would regard his opinions highly.<ul><li><a href="http://www.stoptech.com/whitepapers/rear_brake_upgrade_is_bigger_better120601.htm">Sto pTech - Rear Brake Upgrade</a></li></ul>
Mike,
Since you're going to Stasis, I assume you'll be installing Alcon's -- congratulations, they make great brakes (and of course, so does AP and Brembo).
I'm not really familiar with the '97 A8 brake setup. Do you have the 312x25mm vented rotors in the front, and 245x10mm solid rotors in the rear?
Assuming the above and that Stasis package is a 4-pot Alcon with a 13" rotor -- You probably do not need to upgrade the rear calipers. Even with the stock brakes, for a SINGLE max effort braking stop from high speed, the tires are normally the weak link; and this is confirmed by the fact that ABS should activate to prevent the brakes from locking up. Under these hard braking conditions, 80+% of the car's weight is transferred to the front of the car, and the rear brakes do <20% of the work. If you add wider and/or stickier tires, you can brake even better, the rear to front weight transfer is even larger, and the rear brakes have even less work to do. StopTech has a good "whitepaper" on this subject on their web site (see link).
The only caveat might be if you take you A8 to the track. This is obviously where you'll get the most benefit from the Alcon's; your front brakes just won't fade with repeated hard braking. Under these conditions, though, I'm not as sure about your rear brakes. With the small solid rotors, cooling air flow is minimal, the pads may overheat, and your rear brakes may fade. This isn't a disaster (you're losing <20% of your braking), but it'll be a major nuisance. I'd recommend that at the track you use a high performance racing pad in the rear with the stock calipers, perhaps something like the Pagid RS 4-4 orange. With the solid rotors, though, you may overheat even the Pagid's; but only at that point would I consider upgrading the rear brakes. I'm not sure that I totally trust the specs shown in the AudiWorld models guide, but it says that the '02 A8 has the 245x10mm rear rotor, but vented. If this is true, an excellent rear upgrade may just be to the '02 A8 vented rear rotor.
Last but not least, I've talked at length with Paul Lambert at Stasis about S8 issues. Give him a call; he is very knowledgeable, and I would regard his opinions highly.<ul><li><a href="http://www.stoptech.com/whitepapers/rear_brake_upgrade_is_bigger_better120601.htm">Sto pTech - Rear Brake Upgrade</a></li></ul>
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