mishar

If we forget ceramics more expensive than our cars, Brembo 8 piston, 4 pads with floating rotors used on previous RS models would be my first choice, but they are almost impossible to find and extremely expensive. Same thing with maintenance. Single rotor is more than $350. So the best of the rest are S8/W12 385 mm.

NightOwl

Thanks for explaining, so I guess changing size of the disks won't matter in this case?

NightOwl

Thanks for sharing your knowledge MP4.2+6.0!

Mixing up different models makes my head spinning!

Did some more digging in the parts number, and can't see that any the A4, S4 or RS4 share the same wheel bearing housing as my A8 D3, which makes my worried if the carrier and/or the offset on the disk will fit. Also the RS4 B7 only have mechanical parking brake for the rear, which makes it a challenge.

Although found out that the RS6 C6 share the same wheel bearing housing as the A8 D3, but those disks are 390mm in the front and 356mm in the rear, and probably not easy to find.

Found a pair of W12 calipers including carriers at for 211 GBP each, not sure about the condition or if the price is good as they are from a 2004 model.

MP4.2+6.0

it's just a vague indicator of similarity in the steering knuckle or overall rear hub carrier design. What is critical are 1. the combination of the rotor offsets and the offset built into the hub (which combine to control where the rotor will fall relative to the center of the caliper through which the rotor passes), and 2. the bolt spacing (and diameter) where the caliper bolts up to the steering knuckle.

Reducing it to a few knowns, most of the front Audi designs are basically quite generic and interchangeable at least on the mid and larger models, and for recent generations. Rarely do they seem to play with hub or rotor offsets in front either. Thus the interchange back to the C6 RS6, the cross over to the RS4, etc. The rears can be trickier on the performance models. For example the C5 RS6 rotor (a semi floating design) is 335mm like the D3 W12 or S8, but the offset is different (not sure if in hub or in rotor). Likewise the RS5 rear hub causes an offset difference and makes them non-interchangable to all the B8's, Q5's and A/S 5's, unless the hub itself is swapped. On the rotors, you also have to watch out for the hub diameter change that occurred between D3 and D4, C6 and C7, B7 and B8.

Yes, I think the C6 RS6 set up is basically direct bolt up, but it was never sold in North America, I never see it used on any of the Euro EBays, and was sold in low volume and probably often with carbon brakes anyway.

Your W12 calipers sound like a decent find if they have the carriers too, though sometimes you can find them for less perhaps. Audi sells a rebuild kit for all the hydraulic/rubber parts and it is relatively easy to disassemble (plus paint as desired at the same time); thus age isn't too big a concern if otherwise sound.

Last idea I forgot about: Bentley Continentals are basically a D3 A8 with a blown W12 in heavy drag and a big price tag. They have yet bigger brakes up front (400mm IIRC). Once in a while they show up, at all kinds of both higher and lower prices.

Do be forewarned by the way that the stock W12/S8 rotors are really heavy so you are adding a lot of extra weight, without the HP to go along with it. The rotor alone weighs 39 lbs (almost 18kg) so is really a lot--about ⅔ of a D3 wheel perhaps, and that is just the rotor.

NightOwl

Awesome MP4.2+6.0!

I will be jumping on those W12 calipers if they are not gone already, and the seller also had carriers for the rear too. I've been already thinking to buy a service kit for the calipers and change the rubber and gaskets, so I hope they will be as good as new. Pads and disks are no problem to find here in Norway.

Hm, wonder if they will fit under my 18" winter wheels...

MP4.2+6.0

While you are at it, I would replace the front hoses. You will have them undone anyway as part of a caliper swap out. Not that expensive for standard OE/OES rubber ones given your other parts costs for the upgrade, and by 8 or 10 years old it should firm up the brake pedal a bit.

NightOwl

Good idea!

Panelhead

I need to flush the fluid anyway. The hoses are about 160.00 for front and rear. Pedal is a little mushy.

MP4.2+6.0

There are more hoses in total in the back, and they don't get added strain and movement of the steering like up front over countless cycles over the years.

blankhopp

I thought since this thread is about brakes and sizes I can post a suitable question here. Is there anywhere on the web, preferably in the EU where one can order discs or/and pads for the D3 W12? Perhaps even aftermarket brands?