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  • Brakes - Single or dual circuit?

    The Marina roadster I have just started to rebuild has the original single circuit brakes.
    For safety I would like to change to dual circuit but so far I have failed to find a tandem master cylinder. They seem to be like hens teeth.
    So the questions are:
    Are there any downsides to dual circuit? I know that the dual circuit brakes on a Spifire have a dreadful reputation...
    Where might I find a master cylinder? I have tried all the usual places with no joy.
    As I understand it the bore of the non servo master cylinder is 0.7" (the servo one is 0.75"). Can anyone confirm that?
    At this stage I don't want to consider using a master cylinder from another vehicle, with the associated hassle of modification, as I see some others have done.
    I am also not currently considering a servo although that might change!
    Cheers Robin

  • #2
    Re: Brakes - Single or dual circuit?

    Check out 'Car Builders Solutions' They have lots of info.

    Comment


    • #3
      Re: Brakes - Single or dual circuit?

      If it were me, I would go with a dual master cylinder setup using a servo delete solution like the one from compbrakes.
      CUSTOM REMOTE UNIVERSAL BRAKE BIAS PEDAL BOX KIT [HYDRAULIC - SERVO REPLACEMENT] DUAL CYLINDER [STD KIT] STANDARD BOX KIT INCLUDES – CUSTOM BOX PLUS - [2 X MASTER CYLINDERS, SWINGING PIVOT, CLEVIS, FIXINGS & BALANCE BAR]


      CMB0336-PEDAL-BOX-BIAS-CUSTOM-UNIVERSAL-HYDRAULIC-STD-200x200.jpg

      You would need to upgrade your pedal box to one that was designed to take a servo if yours is a non-servo type.
      Last edited by jon_cox; 26-09-20, 07:02 AM.
      Mk2 SWB Marina Roadster with a 1800 Fiat Twin Cam engine and 5 speed Abarth gearbox built in 1987
      - I have no idea what I am talking about........ but my advice is always free! -

      Comment


      • #4
        Re: Brakes - Single or dual circuit?

        I'm considering updating mine as well. I found that a TR6 servo and master cylinder will fit, or at least I found a reference with pictures of such an installation in the Morris Minor forum where the owner was upgrading to a Marina pedal box of all things. The page can be found here. I'm going down the route of building something like this to get bias adjustment as well as future proofing the installation
        Mk2 SWB Marina Roadster with a 2.0L Pinto built in 1986

        Comment


        • #5
          Re: Brakes - Single or dual circuit?

          I've just read that a master cylinder with servo from a Austin Allegro 73-75 bolts straight on and its dual circuit. Gleaned from Fast Marina site.

          Comment


          • #6
            Re: Brakes - Single or dual circuit?

            Two different beasts

            There are tandem master cylinders - so if one circuit fails you still have the other

            And dual master cylinders where you can have one on each "end" - and change the brake bias front/rear

            As all Marlins have radically different weight distribution to their donor cars IMHO you NEED the dual type so that you can move the brake balance to suit your car

            Comment


            • #7
              Re: Brakes - Single or dual circuit?

              My Roadster is over braked on the front and a suggestion was made to fit a pressure reducer in the font line to balance it. Car Builders IIRC.

              Comment


              • #8
                Re: Brakes - Single or dual circuit?

                Originally posted by HairyDave View Post
                My Roadster is over braked on the front and a suggestion was made to fit a pressure reducer in the font line to balance it. Car Builders IIRC.
                Hmm that's interesting. What is the configuration of your car?
                Cheers Robin

                Comment


                • #9
                  Re: Brakes - Single or dual circuit?

                  Originally posted by duncan View Post
                  Two different beasts

                  There are tandem master cylinders - so if one circuit fails you still have the other

                  And dual master cylinders where you can have one on each "end" - and change the brake bias front/rear

                  As all Marlins have radically different weight distribution to their donor cars IMHO you NEED the dual type so that you can move the brake balance to suit your car
                  Interesting view. The problem is that cars with adjustable brake bias are not road legal in the UK I believe. They are certainly not allowed in the IVA.
                  Cheers Robin

                  Comment


                  • #10
                    Re: Brakes - Single or dual circuit?

                    Robin is correct. However if you use dual cylinders and find the best ballance then weld the adjustment then it will pass as it won't be adjustable....

                    Comment


                    • #11
                      Re: Brakes - Single or dual circuit?

                      It’s worth having a chat with the guys over on the Marina forum, FastMarina.......
                      MOC member since 05/97
                      1984 Marlin Roadster SWB.
                      1800TC, Unleaded ported head, stage 2 cam. Ford Type 9 gearbox, Dolomite Sprint rear axle fitted with MGF disc brakes.
                      Three core radiator, Renault Clio vented front discs.
                      The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man.

                      Loads of Marlin Reference can be found documents here or there.

                      Comment


                      • #12
                        Re: Brakes - Single or dual circuit?

                        Whether a Roadster is overbraked or not on the front axle is not the question. Robin clearly wishes to fit dual circuit brakes for safety reasons and at the moment is unable to source the correct master cylinder.
                        So guys, what are the solutions without resorting to extensive mods to pedal box etc

                        Comment


                        • #13
                          Re: Brakes - Single or dual circuit?

                          Originally posted by martinclan56 View Post
                          Interesting view. The problem is that cars with adjustable brake bias are not road legal in the UK I believe. They are certainly not allowed in the IVA.
                          Cheers Robin
                          My car is not "adjustable" - except by replacing the balance bar - I did some calculations and track testing showed it to be pretty good so I have left it as it was

                          I intend using the same theory on my Marlin

                          Comment


                          • #14
                            Re: Brakes - Single or dual circuit?

                            Originally posted by duncan View Post
                            My car is not "adjustable" - except by replacing the balance bar - I did some calculations and track testing showed it to be pretty good so I have left it as it was

                            I intend using the same theory on my Marlin
                            Do you have such a thing as IVA in NZ?

                            for a new build to be properly registered in the U.K., it’s mandatory. Once registered, you can do what you like, provided you don’t mind driving an illegally modified car, and are not caught.
                            MOC member since 05/97
                            1984 Marlin Roadster SWB.
                            1800TC, Unleaded ported head, stage 2 cam. Ford Type 9 gearbox, Dolomite Sprint rear axle fitted with MGF disc brakes.
                            Three core radiator, Renault Clio vented front discs.
                            The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man.

                            Loads of Marlin Reference can be found documents here or there.

                            Comment


                            • #15
                              Re: Brakes - Single or dual circuit?

                              Originally posted by HairyDave View Post
                              My Roadster is over braked on the front and a suggestion was made to fit a pressure reducer in the font line to balance it. Car Builders IIRC.
                              My suggestion would be to make sure that your rear brakes are functioning at their best.
                              The alleged Marina auto-adjusters are notorious for not auto-adjusting.
                              MOC member since 05/97
                              1984 Marlin Roadster SWB.
                              1800TC, Unleaded ported head, stage 2 cam. Ford Type 9 gearbox, Dolomite Sprint rear axle fitted with MGF disc brakes.
                              Three core radiator, Renault Clio vented front discs.
                              The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man.

                              Loads of Marlin Reference can be found documents here or there.

                              Comment

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