hkgs300

Assuming the size of the new A8, its brakes should be toprated as well. Does anyone know how many pistons these are and the size of its rotors?
Will these bolt-on a A4 (B6)?

skiwi

the d3 a8 v8 uses the new aluminium "fnr" brake. due to the use of a floating frame as opposed to the old "fn" brake, the bridge is much thinner so the a8 can fit a 360mm rotor into a 17" wheel. the v8 has a 2-piston (42mm ea) calliper.

the rear brakes incorporate e-brake, and use the new collette 2 aluminium calliper, with a 310mm rotor and a single 43mm piston calliper.

having driven the d3 a8 v8 in anger i can tell you that the brakes work very well indeed, and the car is noticably better than the new s4 under brakes on a circuit. better than the audi brembos on the s8, no, but then the d3 a8 is not an "s" car either.

the new a6 v8 also uses the "fnr" calliper, with a 347x30mm rotor, and a single 60mm piston in the aluminium calliper. the rears are also e-brake using a collette calliper, but, in light of the better weight distribution of that car, use a 330x22mm rotor and a single 43mm piston calliper.

the trend in the new system is toward increased rotor size (hence better leverage for brakes), reduced piston count, and lighter-weight callipers. (reduced unsprung weight = better ride)

to answer your question, the rears won't work (e-brake), and the fronts will most likely require new hats and calliper off-set. my tip is to check with the friendly folks at bira (www.bira.org), they have a lot of experience in audi brake upgrades.

PaulW

But as Dave says, maybe overall they are lighter?

I can't believe so, but don't know....

<img src="http://www.audipages.com/images/audievent/ae17.JPG">

ryoung

even Mitsubishi can put Brembo calipers both <b>front and rear</b> on the $30k Evo. Even at 2.5x the price, the S8 still didn't get a rear upgrade.

skiwi

visually, the use of the frame, rather than the old thick bridge of the "fn" calliper makes them look a lot more solid than they really are.

howver, these are claerly the "cooking" models, expect better equipment on the s8...

hkgs300

i have seen the Porsche Cayenne 6 piston caliper(basically the same caliper as on the Touareg), and these are huge.
I compared these with the older Brembo designs and the Cayenne's are much lighter than you expect.

I think same also goes for the A8 ones.

skiwi

on my 20v ur-quattro, and lost 5kgs per wheel!

needless to say the quattro, which was a rollerskate at the best of times, suddenly became a rollerskate with much improved ride.

don't underestimate how important reducing unsprung weight (and rotational weight on the wheel - often from upgraded tyre/wheel combinations) is...