Which brake discs?

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  • igor136
    S2Forum Addict
    • Jun 2014
    • 363
    • Country: Croatia

    #1

    Which brake discs?

    Hello people. I have an UrS6 with HP2 brakes. Can you tell me what brand of brake discs you are using with the pads. While I had the OEM discs I had no problems. Now I have OEM brake pads in combination with Ate discs. After hard driving, the discs shake like crazy. Brakes well. Everything is clean, no rust.
    Should I buy Brembo or Audi again? Tnx

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  • Tractor Dave
    S2Forum Zealot
    • Dec 2017
    • 5983
    • Country: Wales

    #2
    ATE are a good brand so I think the problem lies elsewhere. The shake is either warped discs or discs not seated properly. Has it done this from day 1 after fitting? If they have been overheated they could have warped. Are you sure they were genuine? Lots of fake stuff out there. If you have a good dial gauge you can do a run out test whilst on the car.
    Nothelle S2 Avant
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    • igor136
      S2Forum Addict
      • Jun 2014
      • 363
      • Country: Croatia

      #3
      I have done about 1000 km. Then it started.

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      • Tractor Dave
        S2Forum Zealot
        • Dec 2017
        • 5983
        • Country: Wales

        #4
        Originally posted by igor136
        I have done about 1000 km. Then it started.

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        So they have got excessively hot and warped.
        Nothelle S2 Avant
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        • K Simmonds
          S2Forum Zealot
          • Dec 2007
          • 7627
          • Country: Wales

          #5
          Don't wish to seem big headed... However vented discs can not warp under normal driving conditions, they'd have to crack for this to occur... However what does happen is an uneven build up of pad material can accumulate on the surface which expands at a different rate to cast iron and behaves effectively like a warp on a single skin disc. If they were warped it would wobble all the time, hot or cold

          This can happen a couple of ways, brakes that are dragging slightly (sticky caliper) or parking the car up with roasting brake's after a rapid driving session, I did the latter on my S2 a couple of times.

          ATE are a good brand, my personal choice would be Mintex as I can get them at a discount price and the quality is good.

          It's a pain in the backside but if you remove the discs and clean any pad build up off them with some 40/ 80 grit sand paper in a circular motion it should sort the problem assuming that's what causing the wobble and not a cracked pad. Basically a home skim.

          They could also be poorly seated as Dave say's but again I'd expect them to wobble all the time in that case, but not necessarily.

          Quick edit... Check your wheel bolts are torqued correctly, I have encountered brake wobble caused by the bolt torques all being wildly different.
          Last edited by K Simmonds; 5 January 2023, 20:34.
          1990 B3 2.0 80 quattro.
          1992 C4 2.8 Avant quattro
          1994 MTM RS2.
          1998 B5 TDI quattro Sport.
          2000 B5 TQS.

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          • igor136
            S2Forum Addict
            • Jun 2014
            • 363
            • Country: Croatia

            #6
            I always clean everything. The vibration starts after hard braking. The disc may not be compatible with the brake pad. Maybe the friction creates a high temperature.

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            • K Simmonds
              S2Forum Zealot
              • Dec 2007
              • 7627
              • Country: Wales

              #7
              Originally posted by igor136
              I always clean everything. The vibration starts after hard braking. The disc may not be compatible with the brake pad. Maybe the friction creates a high temperature.

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              That's good, so you installed them yourself and we can rule out poor seating or loose/miss torqued wheel bolts?

              I guess it's possible that the pads aren't compatible with the discs, not out of the question, but unlikely.

              I suspect something mechanical is amiss, all I can suggest is to strip them down and inspect everything, make sure the pistons are all nice and smooth in operation and you don't have a damaged pad. Clean the friction surface of disc's as I described and put them back hoping for the best.

              Also closely check the condition of the tyres, inside and out, a damaged side wall could possibly be the cause.
              1990 B3 2.0 80 quattro.
              1992 C4 2.8 Avant quattro
              1994 MTM RS2.
              1998 B5 TDI quattro Sport.
              2000 B5 TQS.

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              • Tractor Dave
                S2Forum Zealot
                • Dec 2017
                • 5983
                • Country: Wales

                #8
                As Kit says, if they are warped you should feel it with gentle braking even when cold. It will be a gentle pulse back on the brake pedal. More noticeable at very slow speed.
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                • newsh
                  S2Forum Obsessed
                  • Aug 2003
                  • 16226
                  • Country: United Kingdom

                  #9
                  As Kit says, actual warping is very rare.

                  Did you get the brakes really hot then hold the car on a hill or at a red light perhaps?

                  If the discs are very hot and the car is held stopped with the brakes applied, the pad material can migrate into the steel.

                  You could try doing a brake “break in” again


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                  • K Simmonds
                    S2Forum Zealot
                    • Dec 2007
                    • 7627
                    • Country: Wales

                    #10
                    Yep, an even build up of pad on the friction surface should be delectable all the time, hot or cold.

                    It is effectively a warp, the only reason I say vented discs can't physically warp is I know I guy who designs and manufactures them and he explained to me in great detail how stable they are as long as they're bolted tightly to a hub and that any vibration caused by the disc itself will be uneven pad build up. Sure if you took one off and chucked it in a furnace it could warp but they are designed so the stresses of each side keep them straight in normal use.

                    All I can suggest is to take the front wheels off and inspect everything very closely, a dodgy pad could be your problem.
                    1990 B3 2.0 80 quattro.
                    1992 C4 2.8 Avant quattro
                    1994 MTM RS2.
                    1998 B5 TDI quattro Sport.
                    2000 B5 TQS.

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                    • igor136
                      S2Forum Addict
                      • Jun 2014
                      • 363
                      • Country: Croatia

                      #11
                      When the brakes are cold, you feel it a little. When they warm up, it shakes like crazy. I disassembled, cleaned and lubricated the brake caliper. Hoses are new. After installation, the discs were warped after 1,000 km, so I took them in for machining. After 2000 km, they warped again. Until then, the braking was perfect. Maybe the only solution is to pay 300 euros for new Audi discs. I had a similar problem with my Audi 100 C3 years ago. Ate discs and Trv pads. I solved the problem with Ferodo pads.

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                      • igor136
                        S2Forum Addict
                        • Jun 2014
                        • 363
                        • Country: Croatia

                        #12
                        The reason may also be passing through water. But I don't remember such a situation. Brakes start to shake during road racing, most often. Speed ​​150 km/h, deceleration to 80 km/h and so 5 times and done. I think they are all bad, recycled materials.

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                        • K Simmonds
                          S2Forum Zealot
                          • Dec 2007
                          • 7627
                          • Country: Wales

                          #13
                          In that case it sounds like you've got uneven pad material build or a warp as it's referred to again, it gets worse when their hot as the material expands more than cast iron. Get them skimmed/cleaned again or do it your with sand paper and try some Ferodo pads by the sounds of it. What a PITA!

                          1990 B3 2.0 80 quattro.
                          1992 C4 2.8 Avant quattro
                          1994 MTM RS2.
                          1998 B5 TDI quattro Sport.
                          2000 B5 TQS.

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                          • igor136
                            S2Forum Addict
                            • Jun 2014
                            • 363
                            • Country: Croatia

                            #14
                            This drove me crazy. Maybe I shouldn't brake?

                            :-/

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                            • Obli
                              S2Forum Buff
                              • Jun 2022
                              • 43
                              • Country: England

                              #15
                              Bosch discs and pads are worth considering too, if looking for OEM+. I bought mine from Autodoc. Didn't realise before but their discs and pads are highly regarded, as one should expect from Bosch, tbh.

                              I think Kit's dead-on with the pad material accumulation rather than warped discs. Warped discs are often, incorrectly the first suspicion. Got to be worth trying a clean-up of the disc faces as described, a squirt of brake cleaner and then reintroduce the disc with the pad progressively by following a bedding in procedure.

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