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  • Brake Pedal Travel Distance

    My 1953 Hardtop has excessive brake pedal travel distance. The car has the Turner front disc brake modificatioin. I have replaced the master cylinder and have bled both the brakes and master cylinder. If I adjust the push rod into the master cylinder to raise the bedal, I get the front brakes draging. Having checked a friends stude with the same set-up and minimal travel distance, I am at a loss at to what might be done to raised the pedal. Currenlty it depresses within about 2 inches of the floor board under normal braking.
    Thanks for any ideas.
    Mike


  • #2
    There's a lot of possibilities here...
    If you can pump it up to a higher pedal, either there's still air in the line or your residual valves aren't working.
    If your rear brakes aren't adjusted correctly, they may require the longer pedal to apply stopping power. Check this first.
    If your front wheel bearings aren't adjusted correctly, the wobble may force the caliper pistons back a bit more than necessary and require more pedal to overcome the gap.

    Once your lines are full and the pads are against the rotor and shoes against the drum, releasing the brake pedal should not allow much fluid back into the MC. The springs in the rear will retract the shoes and residual valve holds the line pressure. The front pads are pulled back by the piston seal, which twists a bit when applied. When the front pad pressure is slacked off, they should still rub the rotor slightly.

    Bob Johnstone
    64 GT Hawk (K7)
    1970 Avanti (R3)

    Comment


    • #3
      There's a lot of possibilities here...
      If you can pump it up to a higher pedal, either there's still air in the line or your residual valves aren't working.
      If your rear brakes aren't adjusted correctly, they may require the longer pedal to apply stopping power. Check this first.
      If your front wheel bearings aren't adjusted correctly, the wobble may force the caliper pistons back a bit more than necessary and require more pedal to overcome the gap.

      Once your lines are full and the pads are against the rotor and shoes against the drum, releasing the brake pedal should not allow much fluid back into the MC. The springs in the rear will retract the shoes and residual valve holds the line pressure. The front pads are pulled back by the piston seal, which twists a bit when applied. When the front pad pressure is slacked off, they should still rub the rotor slightly.

      Bob Johnstone
      64 GT Hawk (K7)
      1970 Avanti (R3)

      Comment


      • #4
        When you replaced the master cylnder. did you follow the instructions and remove the residual/check valves inside the new MC.?

        If you don't then as you adjust the push rod you will get the brakes to drag/lock up. Which MC dd you go with?

        Comment


        • #5
          When you replaced the master cylnder. did you follow the instructions and remove the residual/check valves inside the new MC.?

          If you don't then as you adjust the push rod you will get the brakes to drag/lock up. Which MC dd you go with?

          Comment


          • #6
            yes... I am thinking, you should really have a 2# residual pressure valve on the front lines and a 10# for the rears, with the check valves in the master cylinder defeated if you are using a stock MC... did you do this? If not this is where I would start.

            If you pump the brake pedal does it pump up and then give a good feel? If so I'd be willing to bet this is your issue.

            Also, are you running manual or power brakes? Is the brake pedal matched to your application? (i.e. if you do not have a power booster, do you have a manual brake pedal, or likewise for power?) Using a manual brake pedal with a power booster might also cause a low pedal.

            good luck

            nate

            --
            55 Commander Starlight
            http://members.cox.net/njnagel
            --
            55 Commander Starlight
            http://members.cox.net/njnagel

            Comment


            • #7
              yes... I am thinking, you should really have a 2# residual pressure valve on the front lines and a 10# for the rears, with the check valves in the master cylinder defeated if you are using a stock MC... did you do this? If not this is where I would start.

              If you pump the brake pedal does it pump up and then give a good feel? If so I'd be willing to bet this is your issue.

              Also, are you running manual or power brakes? Is the brake pedal matched to your application? (i.e. if you do not have a power booster, do you have a manual brake pedal, or likewise for power?) Using a manual brake pedal with a power booster might also cause a low pedal.

              good luck

              nate

              --
              55 Commander Starlight
              http://members.cox.net/njnagel
              --
              55 Commander Starlight
              http://members.cox.net/njnagel

              Comment


              • #8
                i used the Jeep master cylinder that is at the top of the list on Turner's web site. There is no power booster invovled. It is all manual. I hasten to add that this work was not done by me but a fellow club member who has a subatantial experience. He has indiccated that he removed the "front" check valve in the master cylinger but not the rear and maintains the rear check valve would not have an effect. There is still an effect from adjusting the push rod. When it was first test driven there was some odor from the brake pads and heating of the front wheels, indicating dragging. The push rod was adjusted to eliminate this but of course any adjustment to lesen this adds to the travel distance.
                This sure seems to be a sensitive installation.
                Thanks again fellows for taking the time to enlighten me.

                Mike

                Comment


                • #9
                  i used the Jeep master cylinder that is at the top of the list on Turner's web site. There is no power booster invovled. It is all manual. I hasten to add that this work was not done by me but a fellow club member who has a subatantial experience. He has indiccated that he removed the "front" check valve in the master cylinger but not the rear and maintains the rear check valve would not have an effect. There is still an effect from adjusting the push rod. When it was first test driven there was some odor from the brake pads and heating of the front wheels, indicating dragging. The push rod was adjusted to eliminate this but of course any adjustment to lesen this adds to the travel distance.
                  This sure seems to be a sensitive installation.
                  Thanks again fellows for taking the time to enlighten me.

                  Mike

                  Comment


                  • #10
                    quote:Originally posted by mdelapp
                    He has indiccated that he removed the "front" check valve in the master cylinger but not the rear and maintains the rear check valve would not have an effect.
                    You don't need a front residual check valve with a firewall mounted MC (if you are running front disk brakes), but you do need one with an underfloor master cylinder (2 pound)...otherwise the fluid in the calipers will siphon back into the MC and you'll have a long pedal stroke to refill the calipers.

                    The rear check valve has a BIG effect. Without one (and rear drum brakes) you will ALWAYS have a long pedal stroke no matter what kind of MC you are running and where it is located. 10 pound is needed on this end.

                    Turner supplies good instructions with his kits AND the proper residual check valves. Your mechanic may be "experienced", but I'd trust Turner's instructions and the parts he supplies with the kit if it was me.


                    Dick Steinkamp
                    Bellingham, WA

                    Comment


                    • #11
                      quote:Originally posted by mdelapp
                      He has indiccated that he removed the "front" check valve in the master cylinger but not the rear and maintains the rear check valve would not have an effect.
                      You don't need a front residual check valve with a firewall mounted MC (if you are running front disk brakes), but you do need one with an underfloor master cylinder (2 pound)...otherwise the fluid in the calipers will siphon back into the MC and you'll have a long pedal stroke to refill the calipers.

                      The rear check valve has a BIG effect. Without one (and rear drum brakes) you will ALWAYS have a long pedal stroke no matter what kind of MC you are running and where it is located. 10 pound is needed on this end.

                      Turner supplies good instructions with his kits AND the proper residual check valves. Your mechanic may be "experienced", but I'd trust Turner's instructions and the parts he supplies with the kit if it was me.


                      Dick Steinkamp
                      Bellingham, WA

                      Comment


                      • #12
                        The brakes had been converted when I bought the car. The existing master cylinder was not one of the recommended one, prompting the change. The new one is indeed mounted under the floor beneath the drivers side door. I will verify the existance of the front ant rear check valves.
                        Mike

                        Comment


                        • #13
                          The brakes had been converted when I bought the car. The existing master cylinder was not one of the recommended one, prompting the change. The new one is indeed mounted under the floor beneath the drivers side door. I will verify the existance of the front ant rear check valves.
                          Mike

                          Comment


                          • #14
                            I agree with Dick. Having Jim's great brakes or dual systems on my small fleet, that 10# check valve's important for the rears.
                            You'll get it, and will be glad you made the conversion, believe me!

                            Western Washington, USA

                            Comment


                            • #15
                              I agree with Dick. Having Jim's great brakes or dual systems on my small fleet, that 10# check valve's important for the rears.
                              You'll get it, and will be glad you made the conversion, believe me!

                              Western Washington, USA

                              Comment

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