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  • #31
    Yeah I have dont pretty much what it says in that article and have had good results. The key as exdos says is not to come to a complete stop and to make sure you can drive for 10 mins after doing the bedding in to let the brakes cool down.

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    • #32
      hi all,

      Quick update; I've taken the car to a BMW dealership and it's been diagnosed as a faulty ABS sensor. Costs = £200.

      Thanks again for all your inputs!

      Adgild

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      • #33
        Update from me as well!

        Tried the re-bedding in technique, and they seemed a bit better, but still some vibration...

        Took it to Indy today, who agree there was a bit of vibration, put it on their hydraulic lift and spun the front wheels, off side front caliper was binding slightly...(certainly more so than the near side)

        So they suggested new discs, pads and a new caliper...

        Questions would be:

        1. Would the binding caliper cause my vibration? They seemed a bit vague on this and said do the pads and discs as well... (guess once caliper is sorted I could try it and see)
        2. Do you normally need new discs (and pads) if it's a caliper sticking?
        3. Is it worth trying new seals in the existing caliper? (do BMW do such a kit?)
        4. If caliper is sorted, and still get the prob, not got much to loose getting the discs skimmed - if I do this should I try new or existing pads?
        5. If I try new pads on skimmed discs (as per 4), and then still need new discs can I use the same pads? (or do I need another set...)

        Sorry for all the q's, but would rather not replace discs and pads as they were only replaced a few thousand miles ago...

        Chrs!Dan
        -------------------------
        Ex Ex Ex: 1998 M Coupé, Estoril/Estoril+Black. HK+ MD+CD Changer, roof, side bags, lamp wash.
        Ex Ex: 1998 M3 Evo Coupé, Estoril / Blk with all the toys.
        Ex: 2004 Z4 3.0i, Silver / blk with no roof.
        Now: 2003 M3 CSL, Silver Grey, lots of carbon fibre.

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        • #34
          Originally posted by danp View Post
          Questions would be:

          1. Would the binding caliper cause my vibration? They seemed a bit vague on this and said do the pads and discs as well... (guess once caliper is sorted I could try it and see)
          2. Do you normally need new discs (and pads) if it's a caliper sticking?
          3. Is it worth trying new seals in the existing caliper? (do BMW do such a kit?)
          4. If caliper is sorted, and still get the prob, not got much to loose getting the discs skimmed - if I do this should I try new or existing pads?
          5. If I try new pads on skimmed discs (as per 4), and then still need new discs can I use the same pads? (or do I need another set...)

          1. Only if it overheats the brakes by binding so badly; this would be felt when trying to drive normally on the motorway through the steering wheel and when you press the brakes. When the brakes cool down it normally goes away until they heat up again when driving. From your original description the vibration is coming from "dirty" discs which is down to the pad.

          2. No

          3. Could be, I've clean up the piston on my caliper and that seemed to work fine, it's also worth just greasing the sliders as this might affect things.

          4. As mentioned earlier in the thread, the OEM discs don't skim easily.

          5. Same pads but as above skimming isn't the best option.

          I had similar brake problems to you; a slight vibration on braking, not huge but it was there. I tried new non-OEM discs that warped and juddered, this was due to a combination of non-floating discs and DS2500 pads. When I plumped for new OEM floating discs all the vibration went away. If the garage wants to change everything (the easiest way to try and cure it!) then probably go for that, but as a start I would get new OEM discs and some decent pads (ie EBC Yellowstuff are good prices).

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          • #35
            Danp,

            You can get a new set of piston seals for your calipers and they are Part Number 34111157037, which cost approximately £15. Interestingly, the same pistons are used on almost the entire BMW product range of models of that era.

            Take a look at the parts in the diagram here:
            http://www.realoem.com/bmw/showparts...57&hg=34&fg=05

            If you don't mind getting your hands dirty, it might be worth your time removing the brake pads and just cleaning off the pistons to remove any rust that might have collected on them. Likewise it would be worth putting a small amount of copper grease on the ends of the tabs on the pads which fit into the slider part of the carriers as well as as on the guiding bolt (part 6 in the diagram. Just make sure you don't contaminate the pads and the discs with any grease.

            Replacing the pads and discs as the first resort does seem a bit drastic, although I'm sure it will resolve the problem.
            /// Exdos ///
            "Men who try the impossible and fail spectacularly are infinitely superior to those who reach for nothing and succeed" --Napoleon Bonapart

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            • #36
              Thanks for the replies c_w and exdos, will try working with what I have rather than replace discs, pads and caliper immediately...

              I'm a bit disappointed that the Indy suggested that, but guess that does tend to be the approach these days unfortunately.
              -------------------------
              Ex Ex Ex: 1998 M Coupé, Estoril/Estoril+Black. HK+ MD+CD Changer, roof, side bags, lamp wash.
              Ex Ex: 1998 M3 Evo Coupé, Estoril / Blk with all the toys.
              Ex: 2004 Z4 3.0i, Silver / blk with no roof.
              Now: 2003 M3 CSL, Silver Grey, lots of carbon fibre.

              Comment


              • #37
                Although I'm never in favour or replacing as much as you can think of to try and solve a problem, sometimes new discs and pads can solve a lot of problems. You say your discs aren't that old though - could you try and post a picture of the discs up? (taken it through the wheel should be ok)

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                • #38
                  Originally posted by c_w View Post
                  Although I'm never in favour or replacing as much as you can think of to try and solve a problem, sometimes new discs and pads can solve a lot of problems. You say your discs aren't that old though - could you try and post a picture of the discs up? (taken it through the wheel should be ok)
                  Sorry took a while..any opinions welcome!

                  http://farm4.static.flickr.com/3246/...5fd652f7_b.jpg

                  http://farm4.static.flickr.com/3177/...ef78ab87_b.jpg

                  http://farm4.static.flickr.com/3205/...a24f48e0_b.jpg

                  http://farm4.static.flickr.com/3054/...cb4a04e4_b.jpg

                  http://farm4.static.flickr.com/3012/...241cecee_b.jpg
                  -------------------------
                  Ex Ex Ex: 1998 M Coupé, Estoril/Estoril+Black. HK+ MD+CD Changer, roof, side bags, lamp wash.
                  Ex Ex: 1998 M3 Evo Coupé, Estoril / Blk with all the toys.
                  Ex: 2004 Z4 3.0i, Silver / blk with no roof.
                  Now: 2003 M3 CSL, Silver Grey, lots of carbon fibre.

                  Comment


                  • #39
                    This is on a CSL? (drilled and floating). They actually look quite "clean" to me - it could be due to the cross drilling that as the disc gets hot the holes are causing vibration but when it cools down they return back to smooth.

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                    • #40
                      Originally posted by c_w View Post
                      it could be due to the cross drilling that as the disc gets hot the holes are causing vibration but when it cools down they return back to smooth.
                      So how do holes in hot discs cause vibration when they don't in cold discs?
                      /// Exdos ///
                      "Men who try the impossible and fail spectacularly are infinitely superior to those who reach for nothing and succeed" --Napoleon Bonapart

                      Comment


                      • #41
                        Originally posted by exdos View Post
                        So how do holes in hot discs cause vibration when they don't in cold discs?

                        I'd imagine as hot metal flexes, more so when it has holes in it ?

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                        • #42
                          The discs are 28mm thick and they will hardly ever get much hotter than 350 degs C which is way under the annealing temperature of cast iron/steel.
                          /// Exdos ///
                          "Men who try the impossible and fail spectacularly are infinitely superior to those who reach for nothing and succeed" --Napoleon Bonapart

                          Comment


                          • #43
                            Originally posted by exdos View Post
                            So how do holes in hot discs cause vibration when they don't in cold discs?
                            Different amounts of expansion when very hot - just a guess as the discs look otherwise in good condition.

                            Taken from a website "Cracking is limited mostly to drilled discs, which may develop small cracks around edges of holes drilled near the edge of the disc due to the disc's uneven rate of expansion in severe duty environments." Whilst those discs haven't cracked if could be tiny differences in surface temperature causing the vibration perhaps.

                            "Hot judder is usually produced as a result of longer more moderate braking from high speed where the vehicle does not come to a complete stop.[16] It commonly occurs when a motorist decelerates from speeds of around 120 km/h to about 60 km/h, which results in severe vibrations being transmitted to the driver. These vibrations are the result of uneven thermal distributions believed to be the result of phenomena called Hot Spots. Hot Spots are classified as concentrated thermal regions that alternate between both sides of a disc that distort it in such a way that produces a sinusoidal waviness around its edges. Once the brake pads (friction material / brake lining) comes in contact with the sinusoidal surface during braking severe vibrations are induced as a result and can produce hazardous conditions for the person driving the vehicle"
                            Last edited by c_w; 11-10-2008, 03:14 PM.

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                            • #44
                              Using my Infra Red thermometer on several different cars, I've found that the discs are only at around 130 degs C immediately on stopping from hard braking from around 120km/hr (75mph). That's not even as hot as a frying pan will get with your breakfast in it.
                              /// Exdos ///
                              "Men who try the impossible and fail spectacularly are infinitely superior to those who reach for nothing and succeed" --Napoleon Bonapart

                              Comment


                              • #45
                                Originally posted by exdos View Post
                                Using my Infra Red thermometer on several different cars, I've found that the discs are only at around 130 degs C immediately on stopping from hard braking from around 120km/hr (75mph). That's not even as hot as a frying pan will get with your breakfast in it.
                                Try repeating that several times on a track even from 75mph if it's heating up in a non-uniform way that might cause vibration.
                                Last edited by c_w; 12-10-2008, 11:11 AM.

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