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Ok Mik, I'll post the write up I did on the old forum, to save navigating to the link:
These are the instructions for the 280mm rear brake upgrade.
PARTS REQUIRED AND COST:
One pair of 280mm Audi A3 front discs VAG part no.1J0 615 301E, I’ve used Zimmerman cross- drilled to match my cross-drilled Porsche front discs (part no. 62373BF from GSF).
Cost - £76.96
These were then machined from 100mm PCD to 112mm (original holes were slotted out) and the central hub hole increased from 65mm to 68mm. This work was carried out by a racecar preparation machine shop but any CNC equipped engineering shop could do it.
Cost - £88.12
Two Audi S8 rear brake carriers VAG part no.W4D0 615 425C, be careful to order the correct ones with this part number as there are two sizes of rear disc used on the S8, 269mm and 280mm, check with Audi.
Cost - £126.74
New longer hub to carrier bolts (4) and 2mm thick 10mm spacing washer’s (4) – explanation later.
Cost - £3
Brake pads, I’ve used EBC Greenstuff, EBC part no.21230.
Cost - £34.16
Brake Calipers, the standard S2 calipers fit the S8 carriers but they are not wide enough to accommodate the 22mm thick disc and new pads - not by a long shot!
I could have trawled around various breakers trying to find some suitable ones (I suspect S4/S6 rears may fit). But I just couldn’t be arsed, after a good few weekends under the car in all weathers doing ‘dry fits,’ I wanted to get the conversion finished.
So I ordered and bought S8 calipers VAG part no. W4D0 615 423 E and W4 615 424 E. These are made of Aluminum as opposed to Iron and a bit lighter than the standard S2 rears.
The S8 has trailing rear calipers and the S2 leading, so the right becomes the left and vice versa, easy!
Cost - £258.50
Not so easy when it came to the flexible brake hoses!
Flexible brake hoses, I’d had new stainless/Teflon ones made up with M10x1.0 male and female hose ends (S2 size). But when I picked up the new calipers I found they required a male M12 hose fitting so an M12 to M10 adapter along with a Dowty bonded sealing washer had to be used in each caliper. The hoses were then remade to fit the adapters (female hose end at both ends, one into the adapter and the other into the existing brake line). These were made up and supplied by Speedflow (020 8530 6664).
Cost – £36.71
Total Cost then of £624.19, far from cheap I know, but if you have more patience than me and source suitable calipers from a breakers (probably any Audi with a 22mm vented rear disc), you can maybe factor around £200 out from that total.
INSTALLATION:
The standard splashguard has to be removed as its too small for the bigger S8 brake carrier. I have my old front ones that were removed for the Movit installation and these fit, but they are in a bit of a mess and really need shot/bead blasting and repainting. I might do this in the future.
The machined discs fit perfectly and having a 37mm top hat instead of 40mm for the standard S2 rear disc they sit a few mm further outboard. This means that when the S8 carriers are bolted on they need to be spaced outboard slightly so that the disc sits centrally within the carrier, on mine it took one 2mm thick stainless washer on each bolt between the hub mount and carrier, but tolerances may vary.
What this also means is that the standard 20mm long fixing bolts will not reach through the carriers, only 2mm short. But it matters.
New long bolts were bought and carefully cut and filed down to approx. 23mm, so that the carriers were properly anchored. Be careful here, as if the bolts are too long they will touch the back of the disc.
The rest is as normal; fit the pads, calipers, handbrake cable and adjust, connect the brake lines and bleed the brakes using a pressure bleeder.
CONCLUSION:
Clearly this conversion is only viable if you have already installed a big brake kit up front (300mm plus). Aesthetically the car looks more balanced; the old 245mm solid discs looked scared cowering inside 18-inch rims.
Talking of balance, I am aware that there may be some issues with front/rear brake bias and a variable bias adjuster may be plumbed in later to fine tune the installation, perhaps with a visit to a four wheel brake dyno for set up.
So far I’m well happy with everything but I do have one niggle.
The pads don’t sweep the whole of the disc face, missing about 6mm on the inside (hub) edge but I’m probably being picky! (The reason the S8 rear disc is not used is because it has a top hat of 46mm and the problems this would cause with spacing have already been discussed on S2 Central forum).
Audi list two part numbers for the 280mm disc pads 4D0 698 451C and 4D0 615 451D the bloke on the parts counter at Audi let me measure a set of C’s (I’m a regular now!) and they are the same dimensions as the Greenstuff pads. They didn’t have a set of D’s, as these are special order for special armored S8’s and over £130 a set!
If any one wants to do this conversion remember tolerances sometimes vary from car to car and although it’s worked for me all disclaimers of course apply.
Finally I hope this may be useful to others out there with bigger front brakes now looking to upgrade the rears.
Thank you to Tommy Arnberg for posting the conversion in the first place on the Audi 20v Kruemmer.
Regards,
Mark.
These are the instructions for the 280mm rear brake upgrade.
PARTS REQUIRED AND COST:
One pair of 280mm Audi A3 front discs VAG part no.1J0 615 301E, I’ve used Zimmerman cross- drilled to match my cross-drilled Porsche front discs (part no. 62373BF from GSF).
Cost - £76.96
These were then machined from 100mm PCD to 112mm (original holes were slotted out) and the central hub hole increased from 65mm to 68mm. This work was carried out by a racecar preparation machine shop but any CNC equipped engineering shop could do it.
Cost - £88.12
Two Audi S8 rear brake carriers VAG part no.W4D0 615 425C, be careful to order the correct ones with this part number as there are two sizes of rear disc used on the S8, 269mm and 280mm, check with Audi.
Cost - £126.74
New longer hub to carrier bolts (4) and 2mm thick 10mm spacing washer’s (4) – explanation later.
Cost - £3
Brake pads, I’ve used EBC Greenstuff, EBC part no.21230.
Cost - £34.16
Brake Calipers, the standard S2 calipers fit the S8 carriers but they are not wide enough to accommodate the 22mm thick disc and new pads - not by a long shot!
I could have trawled around various breakers trying to find some suitable ones (I suspect S4/S6 rears may fit). But I just couldn’t be arsed, after a good few weekends under the car in all weathers doing ‘dry fits,’ I wanted to get the conversion finished.
So I ordered and bought S8 calipers VAG part no. W4D0 615 423 E and W4 615 424 E. These are made of Aluminum as opposed to Iron and a bit lighter than the standard S2 rears.
The S8 has trailing rear calipers and the S2 leading, so the right becomes the left and vice versa, easy!
Cost - £258.50
Not so easy when it came to the flexible brake hoses!
Flexible brake hoses, I’d had new stainless/Teflon ones made up with M10x1.0 male and female hose ends (S2 size). But when I picked up the new calipers I found they required a male M12 hose fitting so an M12 to M10 adapter along with a Dowty bonded sealing washer had to be used in each caliper. The hoses were then remade to fit the adapters (female hose end at both ends, one into the adapter and the other into the existing brake line). These were made up and supplied by Speedflow (020 8530 6664).
Cost – £36.71
Total Cost then of £624.19, far from cheap I know, but if you have more patience than me and source suitable calipers from a breakers (probably any Audi with a 22mm vented rear disc), you can maybe factor around £200 out from that total.
INSTALLATION:
The standard splashguard has to be removed as its too small for the bigger S8 brake carrier. I have my old front ones that were removed for the Movit installation and these fit, but they are in a bit of a mess and really need shot/bead blasting and repainting. I might do this in the future.
The machined discs fit perfectly and having a 37mm top hat instead of 40mm for the standard S2 rear disc they sit a few mm further outboard. This means that when the S8 carriers are bolted on they need to be spaced outboard slightly so that the disc sits centrally within the carrier, on mine it took one 2mm thick stainless washer on each bolt between the hub mount and carrier, but tolerances may vary.
What this also means is that the standard 20mm long fixing bolts will not reach through the carriers, only 2mm short. But it matters.
New long bolts were bought and carefully cut and filed down to approx. 23mm, so that the carriers were properly anchored. Be careful here, as if the bolts are too long they will touch the back of the disc.
The rest is as normal; fit the pads, calipers, handbrake cable and adjust, connect the brake lines and bleed the brakes using a pressure bleeder.
CONCLUSION:
Clearly this conversion is only viable if you have already installed a big brake kit up front (300mm plus). Aesthetically the car looks more balanced; the old 245mm solid discs looked scared cowering inside 18-inch rims.
Talking of balance, I am aware that there may be some issues with front/rear brake bias and a variable bias adjuster may be plumbed in later to fine tune the installation, perhaps with a visit to a four wheel brake dyno for set up.
So far I’m well happy with everything but I do have one niggle.
The pads don’t sweep the whole of the disc face, missing about 6mm on the inside (hub) edge but I’m probably being picky! (The reason the S8 rear disc is not used is because it has a top hat of 46mm and the problems this would cause with spacing have already been discussed on S2 Central forum).
Audi list two part numbers for the 280mm disc pads 4D0 698 451C and 4D0 615 451D the bloke on the parts counter at Audi let me measure a set of C’s (I’m a regular now!) and they are the same dimensions as the Greenstuff pads. They didn’t have a set of D’s, as these are special order for special armored S8’s and over £130 a set!
If any one wants to do this conversion remember tolerances sometimes vary from car to car and although it’s worked for me all disclaimers of course apply.
Finally I hope this may be useful to others out there with bigger front brakes now looking to upgrade the rears.
Thank you to Tommy Arnberg for posting the conversion in the first place on the Audi 20v Kruemmer.
Regards,
Mark.
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