Low pressure on pedal when pushing brakes slowly

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  • e30vert
    E30 Mastermind
    • Jan 2005
    • 1789

    #1

    Low pressure on pedal when pushing brakes slowly

    When I press the brake pedal down slowly and in a linear fashion it will go very far down and almost touch the floorboard. However , if I press it quickly then the pedal does not go very far and I get good firm pedal pressure. Inspected front pads. Tons of life left. Brake fluid is not low as the light above the console would be on and its not. Rear pads have lots of life left. No leaks anywhere!

    Whats going on?

    Sometimes I forget and just push the pedal slowly and it goes way down before I can raise the pedal and reapply quicker. Scares me in stop start traffic at times :D
  • trent

    #2
    Sounds like master cylinder

    I would also check the rear shock mounts, those can sometimes cause wierd problems too

    Comment

    • arsevader
      E30 Enthusiast
      • May 2005
      • 1025

      #3
      Originally posted by trent
      I would also check the rear shock mounts, those can sometimes cause wierd problems too
      Is this somekind of inside joke or are you thinking of another thread. :?:

      The Rear shock mounts have no impact on the travle of the brake pedal.

      James

      Comment

      • trent

        #4
        Originally posted by arsevader
        The Rear shock mounts have no impact on the travle of the brake pedal.
        Actually, you are incorrect. Bad rear shock mounts create much more "dive" under braking (as the shock isn't working keeping the rear end down). If an inexperienced driver isn't familiar with the car, this extra weight transfer moves more weight to the front wheels making braking less efficient and different feeling. Just saying, its a valid option.

        Comment

        • trent

          #5
          Just to prove my point a little more here is a graph relating rear shock mount behavior to breaking effect.



          And if you use the radial acceleration formula you can figure this all out...see this

          Comment

          • arsevader
            E30 Enthusiast
            • May 2005
            • 1025

            #6
            Originally posted by trent
            Originally posted by arsevader
            The Rear shock mounts have no impact on the travle of the brake pedal.
            Actually, you are incorrect. Bad rear shock mounts create much more "dive" under braking (as the shock isn't working keeping the rear end down). If an inexperienced driver isn't familiar with the car, this extra weight transfer moves more weight to the front wheels making braking less efficient and different feeling. Just saying, its a valid option.
            I buy that but I don't buy that bad RSMs are going to cause the pedal to go the floor, no matter how bad they are.

            James

            Comment

            • trent

              #7
              Originally posted by arsevader
              Originally posted by trent
              Originally posted by arsevader
              The Rear shock mounts have no impact on the travle of the brake pedal.
              Actually, you are incorrect. Bad rear shock mounts create much more "dive" under braking (as the shock isn't working keeping the rear end down). If an inexperienced driver isn't familiar with the car, this extra weight transfer moves more weight to the front wheels making braking less efficient and different feeling. Just saying, its a valid option.
              I buy that but I don't buy that bad RSMs are going to cause the pedal to go the floor, no matter how bad they are.

              James
              read my god damn physics proof

              Comment

              • arsevader
                E30 Enthusiast
                • May 2005
                • 1025

                #8
                Originally posted by trent
                Just to prove my point a little more here is a graph relating rear shock mount behavior to breaking effect.



                And if you use the radial acceleration formula you can figure this all out...see this

                You lost me at "Just to prove......" ;)

                James

                Comment

                • AdamF 88iS
                  R3VLimited
                  • Oct 2003
                  • 2051

                  #9
                  Originally posted by arsevader
                  Originally posted by trent
                  Originally posted by arsevader
                  The Rear shock mounts have no impact on the travle of the brake pedal.
                  Actually, you are incorrect. Bad rear shock mounts create much more "dive" under braking (as the shock isn't working keeping the rear end down). If an inexperienced driver isn't familiar with the car, this extra weight transfer moves more weight to the front wheels making braking less efficient and different feeling. Just saying, its a valid option.
                  I buy that but I don't buy that bad RSMs are going to cause the pedal to go the floor, no matter how bad they are.

                  James
                  Do you have a sense of humor? Just busting your balls man. Master cyl it is.
                  Adam Fogg- '88 M3

                  Common sense- It's the new 'gifted'

                  Comment

                  • arsevader
                    E30 Enthusiast
                    • May 2005
                    • 1025

                    #10
                    Originally posted by AdamF 88iS
                    Do you have a sense of humor? Just busting your balls man. Master cyl it is.
                    Hence my original question about the joke. :D

                    James

                    Comment

                    • AdamF 88iS
                      R3VLimited
                      • Oct 2003
                      • 2051

                      #11
                      Trent = the next Ove Kvam.

                      And if you know what i'm talking about you are a true OG.
                      Adam Fogg- '88 M3

                      Common sense- It's the new 'gifted'

                      Comment

                      • arsevader
                        E30 Enthusiast
                        • May 2005
                        • 1025

                        #12
                        Originally posted by AdamF 88iS
                        Trent = the next Ove Kvam.

                        And if you know what i'm talking about you are a true OG.
                        I know Ove but I don't know "OG". Maybe I'm just a dumbass.

                        James

                        Comment

                        • AdamF 88iS
                          R3VLimited
                          • Oct 2003
                          • 2051

                          #13
                          Trent is the bomb.
                          Adam Fogg- '88 M3

                          Common sense- It's the new 'gifted'

                          Comment

                          • AdamF 88iS
                            R3VLimited
                            • Oct 2003
                            • 2051

                            #14
                            Originally posted by arsevader
                            Originally posted by AdamF 88iS
                            Trent = the next Ove Kvam.

                            And if you know what i'm talking about you are a true OG.
                            I know Ove but I don't know "OG". Maybe I'm just a dumbass.

                            James
                            Original Gangsta. Not one of these newbie mofos.
                            Adam Fogg- '88 M3

                            Common sense- It's the new 'gifted'

                            Comment

                            • arsevader
                              E30 Enthusiast
                              • May 2005
                              • 1025

                              #15
                              Originally posted by AdamF 88iS
                              Originally posted by arsevader
                              Originally posted by AdamF 88iS
                              Trent = the next Ove Kvam.

                              And if you know what i'm talking about you are a true OG.
                              I know Ove but I don't know "OG". Maybe I'm just a dumbass.

                              James
                              Original Gangsta. Not one of these newbie mofos.
                              Awsome, I feel special. I've never been called a Gangsta before.

                              James

                              Comment

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