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OK that's understood - I don't mind machining A3 or Beetle discs just for the correct bolt pattern. I assume that is all required...
Paul
Paul,
You also have to machine the centre bore. Obviously if you are going to chomp them down to 269mm as well that going to be another maching operation to pay for. See the pics in the other link.
No handbrake cable issue with the Coupe as they are leading. There will be on the Avant as the calipers are trailing.
OK - thanks for confirming the diamater reduction as well. I spent a few frustrating minutes on the family album looking for a 269mm front disc for the A3. Dohhh - then I figured it must be machine ops on the A3's 280x22mm disc.
Looking at 1K0 615 301S as the best option here for discs.
Aaaah - just noticed that MarkH used 1J0 615 301E with the 5x100 pattern which he machined to 5x112. The 1K0 615 301S already has 5x112 - but I dunno if the hat height is the same. Darn.
The 1K0 discs came in for MY04 and do run with different numbered calipers - whilst it all looks the same the dimensions might be different. Guess I'll have to hunt down a brake specialist catalog now to bottom this out....
As I posted a couple of days ago, I have just completed a 280mm-rear brake upgrade.
I have been running the 322mm Movit Porsche/Brembo front brake conversion since August 2001, a bit expensive, but none the less a very effective improvement over the OEM front brakes.
This left the rear brakes in need of some attention and it was while recently reading through the message postings in the Audi 20v Kruemmer (thanks to S2 Central tech files for that link) that I came across message numbers 319,324 and 342.
These were posted by Tommy Arnberg detailing plans for a rear brake upgrade using an Audi A3 280mm front disc. Originally these proposed the use of this disc (37mm top hat) and having it machined down to 269mm and PCD re-worked from 100mm to 112mm along with the central hub hole from 65mm to 68mm.
However the last message states that the disc can be used at 280mm with the Audi S8 brake carrier with just the PCD and hub locating hole re-machined.
I've been looking for an alternative to the standard rears for some time, so I decided to 'take the plunge' give it a go, here's how it went.
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 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.
I'm fairly new to the Internet, so thank you to S2 Central for an excellent site and also to Tommy Arnberg for posting the conversion in the first place on the Audi 20v Kruemmer.
This is all good stuff, but its easier to do this with the '8E0' rear disc from neu S4/Cabrio... It comes in 300mm x 22 with the 5x112 PCD and has near perfect offset for application on rear of the S2 Coupe. All that is needed is to reduce disc diamater to 280mm for the Coupe. Works with the same carriers listed by Mark and same little washer/spacer trick to get the offset bang on.
The same 8E0 disc can be used at full size of 300mm with the 8E0 carriers and calipers on the S2 Avant or Sedan with no other modifications as the handbrake mechanism is suitable for that. It doesn't work at 300mm on the Coupe due to the handbrake location. This puts the price up considerably for an Avant/Sedan application but you are getting even bigger discs and pistons of course.
Do a search on '8E0' rear upgrade for more info. I actually used UrS6 rear calipers for my conversion on the coupe instead of the superlite sexy allow A8/S8 ones listed by MarkH.
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