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My EBC green rears produce almost zero brake dust - actually EBC compounds generally seem very good for dust, the EBC Reds I had up front for a while produced noticably less dust than my Ferodos do now.
£20 for a pair of rear discs is pretty damn cheap really.
Ex S2 owner, now running around in an A4 Avant quattro...
Unless you change the brake bias towards the rear with a tilton or other adjustable brake bias valve, I believe that something like >80% of the braking is done by the front brakes.
So any changes to the rear beyond a well functioning factory setup is bling.
Peter S
1990 ErsatzS2 - track toy
1991 Coupe Quattro
1991 Coupe Quattro
1995 S6 Sedan
1995 S6 Wagon
Well I can't say that I agree on all this. If there was no point in having brakes at the rear, well... Guess what? There wouldn't be a single car produced today with brakes at the rear.
Now, when converting to big brakes at front (in this case AP's) means that you WILL ruin the brake bias. At least if you concider the original brake bias, the one Audi once intended it to be. Yes, you might actually get a gain in total brakeforce. But the bias will be leaning even more to the front.
All the dough that bought you those brakes actually paid off in the sense that you gained braking force/controllability. But the front brakes on your car will be doing "all" the braking. Let's face it, front tires will wear more than they should. It will lean even more towards understeer. Oh and another thing - what about the ABS-unit?
I'd say that the rears should be proportionally as much bigger as the fronts, both in clamping force and disc size. This way you'll get a brake bias that is at least closer to the one Audi intended. I mentioned the ABS unit? Yeah, sure it'll work in most cases. But in some cases it will go bananas. And ONE SINGLE FAILURE WILL BE ENOUGH.
However. The ABS unit gives you a degree of freedom in the sense that it will be able to handle some of the built-in difference in brake bias. But I sure wouldn't lean on that. I've seen too many strange brakedowns due to wierd things you couldn't possibly even begin to believe would matter to a ECU. Sorry. These things fu€$ up. Period. Never heard of that before? Don't read it out loud. Don't think about it. The minute you're aware of the fact that it might happpen it will happen. A system controlled by a software is never better than the hardware the system is built with. You can do alot with software and a good regulator. Maybe Harry Potter can wave his wand and sort everything out. The ABS unit can't. Trust me. It can't. Not even with the correct brake bias.
Bling or no bling - 18" wheels with big discs and good decent calipers look great and feel great. Stock brakes with 18" wheels in the rear looks...well strange at best. Possibly wierd. I'd have to go with really wierd. Wierd and strange.
To sum up. Sure, I've seen all the cool cars with big fronts and no rears. I've been told I'm a loser for even caring about the rears. I've even been on the other end on this matter (which BTW was a discussion about fitting huge rear brakes on a Beetle to get a more rear ward bias on the brake system to be able to run super skinny 125's up front and 225's out back). I still don't want to cruise down the road at 150mph with no rear brakes. I believe there is a reason that cars actually do have rear brakes that are in proportion to the fronts.
Henka is right...
But just putting larger rears on after putting larger fronts on doesnt mean that they will be used...without stiffening the suspension ( does your car nose dive under braking?) and/or changing the brake bias so that you can USE those new rear brakes...
Peter S
1990 ErsatzS2 - track toy
1991 Coupe Quattro
1991 Coupe Quattro
1995 S6 Sedan
1995 S6 Wagon
Below you will see two possible ideas for rear vented rotors. I tried a couple of different calipers and rotors, basically running with ideas I got from other original thinkers on other forums.
These are a couple of different combinations using two different rotors, two different calipers, both...
I am using the S4/6 rear caliper on a S8 caliper carrier with a bored and punched VW60 front rotor.
I have run two track events with my new brakes. For the first one, I just ran my Mintex Reds that I use on the street. No fade. The second event I ran Carbotech Panther Plus pads. The car braked even better and no fade. One of my instructors at the second Audi Driving School runs an S4 with Stoptech front calipers, Stoptech 322X30 rotor and Porterfield RS4 racing pads. Her rears were the standard S4 brakes. The comment I keep getting from her was that my car braked better than hers. Her Porterfield Pads were history after the event. They were all cracked. Now I am running a lighter car, so that may have something to do with some of it. But my brakes work really well. Both my instructors kept trying to tell me to brake earlier. I showed them I could brake a lot later than they thought. They were comparing my car to theirs, and I had better brakes.
I just got back from the second event. My car is sitting in the garage. The rear wheels show more dust than the fronts. Personally, I think the rear do their part of the job. If rear were not needed, why did the manufacturers install discs on the rear, instead of staying with drums.
My set up is basically the same sizes as the A8. 323 fronts with 280 rears and the car weighs a lot less.
Just my 2 pence.
Greg
They can have my car when they pry my cold dead fingers from the steering wheel.
Henka, Understand exactly what you are saying. I dont plan on using the ABS if i can help it though. Afterall its not ment for normal braking just in emergencies. Nose dive wise there is very little since all of the suspension has been done now too.
Greg, approximately how much did it cost to make you rear setup?
What I was trying to say is that the most cost-effective way of improving your braking is to uprate the fronts - you get a huge increase in brake perfromance for a reasonable outlay. Uprating the rear is very small beer in terms of overall brake performance improvement, (ie, for example if you imrove rear braking force potential by 50%, it's still only 50% of the 20% contribution to the overall braking of the whole carand compared to the front) it's also less of a clear upgrade path.
Most normal cars have disc brakes on the rear these days because the marketing men say that disc brakes look "better" and therefore will help sell more cars. It's exactly the same arguement as why some manufacturers x-drill their discs on their road cars when it really doesn't make enough of a difference to normal road use to justify the increase in cost and the reduced life of the disc. It does, however, look more BLING and people are sucked in to thinking that because BMW M3s have x-drilled discs, it MUST therefore be better.
The reason that so many rear calipers on so many cars fail is because they never get enough use to actually move properly and so they seize.
The S2 is a heavy, front-heavy car - you get huge weight transfer forwards under braking. Put more brake power up there (and more grip through bigger/ wider tyres), you'll get a lot of extra braking. Put more braking up at the back, which under hard braking gets lighter and lighter as the weight transfers forward and you actually stand the chanece of the rears locking earlier than the fronts and confusing the ABS even more!
My most recent track-day experience up against another S2 was to be on the track at the same time as Lee with his 6pot APs, vs. my 4-pot, smaller disced (304mm) Brembos. Both of us have stock rears. From 140mph, Lee was braking about 30metres later than me and still making the same turn in and apex as I was. His investment in even bigger front brakes clearly paid dividends.
Ex S2 owner, now running around in an A4 Avant quattro...
Also if you are interested I just took out of the car a set of Tarox G88 (grooved) rear disc for OEM setup. I also have 2 sets (one used almost nothing 1000 miles max, same at disks) and another still in box of EBC red stuff pads for the rear of the S2. I did not find any problem with dust and they are better than the green stuff.
I will give them away for almost no money.
60 Euro + shipping for 2 discs almost new and 2 sets of rear pads EBC red.
They do brake better than OEM. I used them for 1000 miles together with the big reds at the front while I was sorting the rear setup. PITA it has been those rears, but well worth it. Will test it next week at last!!!
Greg, approximately how much did it cost to make you rear setup?
ta
Greg S,
It is hard to say. I had the UrS6 caliper from a car I was parting out. So no cost except for the rebuild kits. I don't imagine these would cost much more than a 100USD for a set of used ones.
The Corrado rotors I got from a guy for nothing when I bought G60 front hub carriers for my kids Jetta MKII. They still had 1mm of rotor thickness left above the minimum so I had them bored and punched.
The slotted/plated New Beetle rotors were 250USD for the pair. It cost me 40USD to have the center bore enlarged from 65mm to 68mm and the lug holes slotted. You need to remember that the center bore has a rounded taper to fit on the hub carrier. You have to make sure the machinist does the rounded taper and doesn't just enlarge the center bore.
The S8 caliper carriers were 126USD for the pair.
Of course, pad cost depends upon what you want to use.
Hope that helps.
Greg W.
They can have my car when they pry my cold dead fingers from the steering wheel.
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