Hat height on front discs

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  • s2driveruk
    Super Moderator
    • Jul 2003
    • 12696
    • Country: England

    #16
    @ Corey, my calipers are monoblock Brembo 4 pots with 4 x 40mm pistons and the part number 20.7926.01 & 02 Ever come across them before? Would it seem unusual for them to have the same size piston. Pics on this thread: http://www.s2forum.com/forum/showthread.php?t=3048


    Cheers,

    David
    sigpic

    1992 3b S2 Coupe

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    • 91_S2
      S2Forum Maniac
      • Jul 2003
      • 612

      #17
      Originally posted by s2driveruk
      Would it seem unusual for them to have the same size piston.

      Cheers,

      David
      According to Carroll Smith (who probably knows or knew since he is dead) different sized pistons evolved in order to achieve even pad wear. The trailing edge is hotter IIRC. In time you got a wedge shaped pad. Different size pistons gives a pressure gradient from the leading edge to the trailing edge.

      Perhaps modern pad materials wear more evenly and don't need the gradient. Perhaps it is practical for the factory to be able to use a single caliper both left and right.

      Comment

      • Corey
        Banned
        • Sep 2003
        • 2793
        • Country: United Kingdom

        #18
        Originally posted by 91_S2
        According to Carroll Smith (who probably knows or knew since he is dead) different sized pistons evolved in order to achieve even pad wear. The trailing edge is hotter IIRC. In time you got a wedge shaped pad. Different size pistons gives a pressure gradient from the leading edge to the trailing edge.

        Perhaps modern pad materials wear more evenly and don't need the gradient. Perhaps it is practical for the factory to be able to use a single caliper both left and right.

        Very unusual to have the same size piston, not come across it before.

        Nothing at all to do with modern pad material, you will still end up with wedge shaped pads.

        Greg,
        No! I think it is one of those urban myths, unless anyone else can shed some light? 330x30 Audi oe disc? Part numbers only.
        Corey
        01636 822288

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        • 91_S2
          S2Forum Maniac
          • Jul 2003
          • 612

          #19
          Originally posted by Corey
          Very unusual to have the same size piston, not come across it before.

          Nothing at all to do with modern pad material, you will still end up with wedge shaped pads.

          Greg,
          No! I think it is one of those urban myths, unless anyone else can shed some light? 330x30 Audi oe disc? Part numbers only.
          Sorry. I had a hard time understanding your post.

          Are you saying that you will still get wedge shaped pads with the same piston sizes or different piston sizes or both?

          Comment

          • s2driveruk
            Super Moderator
            • Jul 2003
            • 12696
            • Country: England

            #20
            Originally posted by 91_S2
            Sorry. I had a hard time understanding your post.

            Are you saying that you will still get wedge shaped pads with the same piston sizes or different piston sizes or both?
            Hmm, looking at the pads which came from the calipers, there's no sign of uneven wear? They are a ferodo/Bembo pad, p/n XA0.40.79 and have the number 4446 (might be a compund number?) Interestingly, the pad has a arrow (i guess for direction of rotation) but the caliper does not

            If anyones interested, I came across this sites yesterday, quite useful for brembo calipers (racing stuff - non porsche branded)



            Cheers,

            David
            sigpic

            1992 3b S2 Coupe

            Comment

            • 91_S2
              S2Forum Maniac
              • Jul 2003
              • 612

              #21
              Originally posted by s2driveruk
              Hmm, looking at the pads which came from the calipers, there's no sign of uneven wear? They are a ferodo/Bembo pad, p/n XA0.40.79 and have the number 4446 (might be a compund number?) Interestingly, the pad has a arrow (i guess for direction of rotation) but the caliper does not

              If anyones interested, I came across this sites yesterday, quite useful for brembo calipers (racing stuff - non porsche branded)



              Cheers,

              David
              Interesting link David

              Comment

              • Corey
                Banned
                • Sep 2003
                • 2793
                • Country: United Kingdom

                #22
                Originally posted by 91_S2
                Sorry. I had a hard time understanding your post.

                Are you saying that you will still get wedge shaped pads with the same piston sizes or different piston sizes or both?

                What I said was,

                I would assume that with pistons of the same diameter on one caliper you would end up with uneven pad wear.

                But I am willing to be proven otherwise???

                Also though, if you mount Monoblocks incorrectly with the pistons not in the correct orientation again you would get uneven pad wear.

                Hopefully I have made myself clear?
                Corey
                01636 822288

                Comment

                • s2driveruk
                  Super Moderator
                  • Jul 2003
                  • 12696
                  • Country: England

                  #23
                  Found out a bit more about these calipers, they are from the new Renault Sport Megane 225 which is why there is probably almost no info on them anywhere on the net. Checking the piston sizes and the codes from the dust seals they are definately 4 x 40mm pistons.

                  I spoke to the local Renault Dealership today and they are getting a new parts cd update at the end of the month which should hopefully be able to give more details on the caliper etc.

                  If they fit ok, yet to be seen but fingers crossed then it could be a new upgrade possibility.....

                  I'm pretty sure this is the only (maybe first) brembo monoblock with the same sized pistons on all 4 pots. I guess the piston pressure could just be slightly staggered on their application of pressure to the disc - certainly nothing to see on the pads i had taken out to indicate uneven wear rates etc.

                  Keep you posted on details and fit...

                  Cheers,

                  David
                  sigpic

                  1992 3b S2 Coupe

                  Comment

                  • Corey
                    Banned
                    • Sep 2003
                    • 2793
                    • Country: United Kingdom

                    #24
                    I must admit to wondering if the ports for the pots had some sort of staging, but it was a Batman moment after my last post on this thread.
                    Corey
                    01636 822288

                    Comment

                    • s2avant
                      S2Forum Fiend
                      • Jul 2003
                      • 2426

                      #25
                      Originally posted by s2driveruk
                      Found out a bit more about these calipers, they are from the new Renault Sport Megane 225 which is why there is probably almost no info on them anywhere on the net.
                      Off topic (sorry). I was following one of those Renault Sport Megane 225 the other day on my way home from work. He didn't push it so don't how well it went but I did notice the exhaust wobbled about all over the place. It looked as thought the two holes in the bumper that the tailpipes poke through was the only thing holding the back box on

                      Ben
                      the best intentions are fraught with disappointment - gil grissom

                      sigpic
                      1994 ABY Avant - it's getting there

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                      • s2driveruk
                        Super Moderator
                        • Jul 2003
                        • 12696
                        • Country: England

                        #26
                        thank god brembo built the brakes then
                        sigpic

                        1992 3b S2 Coupe

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                        • Greg_S
                          Administrator
                          • Jul 2003
                          • 12430
                          • Country: United Kingdom

                          #27
                          i think i have found a suitable set of 330 x 32mm discs. im gonna go do some more research on them tommorow.

                          Greg
                          Greg

                          S2Forum.com Administrator & Webmaster

                          '93 Coupe with a few tweeks

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                          • Stick Insect
                            S2Forum Fiend
                            • Dec 2003
                            • 2338
                            • Country: United Kingdom

                            #28
                            Originally posted by s2avant
                            I did notice the exhaust wobbled about all over the place. It looked as thought the two holes in the bumper that the tailpipes poke through was the only thing holding the back box on

                            Ben
                            French init!

                            D.

                            Comment

                            • Corey
                              Banned
                              • Sep 2003
                              • 2793
                              • Country: United Kingdom

                              #29
                              Originally posted by Greg_S
                              i think i have found a suitable set of 330 x 32mm discs. im gonna go do some more research on them tommorow.

                              Greg
                              Greg, if it is 32mm wide you will need to use the caliper from a 996 tt, not the standard Carrera.
                              Can you inform what the hat height is also, ie from the back face of the hub mounting to the inner face of the disc.

                              TIA

                              oh! and well done!!!
                              Corey
                              01636 822288

                              Comment

                              • Greg_S
                                Administrator
                                • Jul 2003
                                • 12430
                                • Country: United Kingdom

                                #30
                                Im gonna try get my hands on one to take some measurements, it happens to be a merc disc and can get a pair either drilled, grooved or both for about £160.

                                Will the calipers from a GT3 be suitable?
                                Greg

                                S2Forum.com Administrator & Webmaster

                                '93 Coupe with a few tweeks

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