Rear Disc Brake Overhaul

On the Coupe Q i was finding when braking from speed I was getting the feeling that I wasn't going to stop in time and that just about anything else could stop better than me. After a bleeding session and replacing the brake pressure proportioning valve things did improve for around 6 months, after which the same problem returned. I looked at both front and rear brakes, upon inspection the rear discs looked discoloured with a blackened look about them, the outer edges were also very corroded (seen a few salty winters). So it was time to order some new parts, I thought there would be no point in putting new pads on crappy old discs, so I ordered new ATE discs and pads.
First job is to get the old pads out on the right rear, no problem really just undo the 13mm headed bolt and hold the guide pin with a 15mm open ended spanner. Next problem was to remove the brake caliper carrier attaced to the hub with two 8mm allen or hex headed screws. The top one came out fine with a key and long bar, the bottom one however I could see was badly corroded and already a bit chewed by some other monkey lad who had replaced them 3 years ago. Anyway treid the allen key and long bar, not a chance in hell of it moving, nothing else to do but get the power drill and grinding stone on to it. Forty minutes later I have the bracket in my hand and onto the bench vice, liberally sprayed with WD40 to get the rest of thread out, what I used here was a big pair of water pump pliers.
Whilst it was in the vice I gave it a good clean with a wire brush and then copper greased the parts that the brake pad touches, next i gave the hub a wire brush too to get any old dirt and rust off that would prevent the new disc from seating properly. Next job is to wind the caliper's piston back in to accomodate the new thicker pads and disc, to do this I ground down on my bench grinder a 12mm allen key to 11mm and the pushed and turned at the same time the piston back in (sfter removing the brake fluid cap first), then I replaced the rear disc, first getting off the oily protective film with methylated spirit and then refitted the brake caliper carrier, NB the screw I ground off was replaced with one from a Golf GTI from the scrapper, these screws are I think metric fine and are hard to get hold of other than from a dealer. Next up was to fit the new pads after applying a coating of copper grease being careful not to get this on the surface of the disc. Then replace the caliper using two new bolts with locking compund on them (they should be supplied with the new pads). Now refit the roadwheel with two bolts and make sure they are tight enough to allow the wheel to rotate, next pull on the handbrake a couple of time and pump the brake pedal to get the new pads onto the disc, now rotate the wheel to make sure they do not bind unduly.
Having now done one side please put in the remaining whell bolts lower the car and torque these to 80 to 85 ftllbs of torque. Now onto the other side, if like me you find another one of caliper bracket bolts seized then it will out with the grinding tool again, in hindsight I would advise you get four new ones from Audi before you start and replace them as a matter of course. In the course of doing both sides I also removed the calpier guide pins and cleaned the old grease off rubbed any rust down and regreased them, I found two to be seized solid, no wonder my brakes didn't work very well. In addition the state of the discs were really bad too.
You may also find that the handbrake needs some adjustment, this is best adjusted using a 10mm deep socket and extension bar of around 10inches to gain clearance under the car, I found mine to be too loose, both of the cam's on the handbrake mechanism should be on thier respective stops after adjustment.
The end result is very satisfying, I now have a good solid brake pedal feel and I can actually feel the rear brakes doing thier job properly. I now get a lot more brake dust on the rear wheels than ever before so I know all is working correctly.
Always remember when working underneath any car, make sure it is supported correctly, not just using the trolley jack or whatever, use axle stands.


Photos available when I make them........



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Copyright 1999 Iain and Ralf
Dec. 1999