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    Brake Bias setting

    Upgraded the front brakes on the xr6t. Brembo 6 piston, all 40mm (yes all the same) on 355/28 rotors, rears are territory calipers, single 45mm on 328/28 rotors.

    First time out with stock booster gave me a really long pedal inspiring no confidence. Came home and bought a wildwood 7:1 pedal that came with 3 x 7/8th cylinders which I figured were a good place to start (with no technical support to prove this being correct). I'm about half way through mounting and realised getting brake lights to work wasn't simple so picked up a wildwood proportioning valve with a light sender. My logic is the rears will have higher line pressure due to the smaller caliper so I can reduce this to even out bias and then use the balance bar to fine tune things.

    Does all of this sound like it will work ok? I was going to set line pressures in the shed to get them close but what is a good starting point given falcons are nose heavy?

    #2
    Pressure has nothing to do with the caliper
    Its to do with the master
    Smaller master... higher pressure
    So if your running the same front and back... same pressure
    Though... balance will determine when the light comes on
    You'll need to play with master cyl sizes when you get it working to get the balance right

    What caliper... never seen a Brembo with 6 pistons the same size
    Location Perth Western Australia

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      #3
      long pedal sounds like air in the system,
      2017 Ford Ranger XLT (Jeep Wrangler recovery vehicle)
      2007 KTM 250 SX

      Originally posted by Monza
      I've never considered myself the type of guy to eat arse but I am currently reviewing that policy

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        #4
        ran a litre of fluid through the system and it never came up. abs plumbing might have been being difficult so dunno. car stopped, just in the last 20% of movement

        Sent from my SM-G970F using Tapatalk

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          #5
          Originally posted by dattoman1000 View Post
          Pressure has nothing to do with the caliper
          Its to do with the master
          Smaller master... higher pressure
          So if your running the same front and back... same pressure
          Though... balance will determine when the light comes on
          You'll need to play with master cyl sizes when you get it working to get the balance right

          What caliper... never seen a Brembo with 6 pistons the same size
          jeep srt caliper.
          I was thinking with balance bar level the rears will build pressure quicker and therefore potentially lock before fronts get to that pressure level. does that make sense?

          Sent from my SM-G970F using Tapatalk

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            #6
            Long pedal is because the front master cylinder is now too small, and it can't displace enough fluid for the increased piston area surface in the new front calipers.

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              #7
              Originally posted by Sprinkles View Post
              Long pedal is because the front master cylinder is now too small, and it can't displace enough fluid for the increased piston area surface in the new front calipers.
              Thanks, volume was creeping into my thought process along the same lines you've described.

              Sent from my SM-G970F using Tapatalk

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                #8
                I'm prepared to fuck around with many things without knowing what i'm doing, but brakes are not one of those things.

                Oo___oO

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                  #9
                  Have a look at the sizes used on the SRT - will give you a starting point for what size master/rear should be. You can spend a lot of time farking around with this.

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                    #10
                    People like you scare the fuck out of me, not the simplest understanding of what you are doing.

                    There is no such thing as a "Brake Proportioning Valve" it is simply a pressure limiting valve it sets a maximum pressure for that circuit.

                    It's going to be a pretty radical set up you end up with, with 12 x 40mm caliper pistons on the front and 2 x 45mm pistons on the rear.

                    Good Luck

                    P.S. how much does the Falcon weigh?
                    " Racing cars don't have doors. Toilets have doors" : Keke Rosberg

                    Comment


                      #11
                      Originally posted by Sprinkles View Post
                      Long pedal is because the front master cylinder is now too small, and it can't displace enough fluid for the increased piston area surface in the new front calipers.
                      Not really but letís work it out so we can solve this. The total volume of the MS isnít displaced each time you apply as the system is closed. Itís actually the ratio of the MS to the caliper that provides the increased force.

                      OP; whatís the three piston diameters and whatís the previous caliper two pistons diameter.

                      I still reckon thereís air in the system
                      2017 Ford Ranger XLT (Jeep Wrangler recovery vehicle)
                      2007 KTM 250 SX

                      Originally posted by Monza
                      I've never considered myself the type of guy to eat arse but I am currently reviewing that policy

                      Comment


                        #12
                        Originally posted by Roy928tt View Post
                        People like you scare the fuck out of me, not the simplest understanding of what you are doing.

                        There is no such thing as a "Brake Proportioning Valve" it is simply a pressure limiting valve it sets a maximum pressure for that circuit.

                        It's going to be a pretty radical set up you end up with, with 12 x 40mm caliper pistons on the front and 2 x 45mm pistons on the rear.

                        Good Luck

                        P.S. how much does the Falcon weigh?
                        I understand the logic behind the setup and the bias isn't great with what I have. I enjoy figuring it out and making what I have work. However I also understand there is some maths involved here and asking advice from people with more experience fast tracks my learning. Yes I may be brave but I'll test on a quiet track day before going nuts.

                        Weight would be around 1500-1550kg

                        Sent from my SM-G970F using Tapatalk

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                          #13
                          Originally posted by Greg Rust View Post
                          Not really but letís work it out so we can solve this. The total volume of the MS isnít displaced each time you apply as the system is closed. Itís actually the ratio of the MS to the caliper that provides the increased force.

                          OP; whatís the three piston diameters and whatís the previous caliper two pistons diameter.

                          I still reckon thereís air in the system
                          brembos run 6x40mm pistons, yes they're all the same.

                          Google won't tell me what the stock twins are but I reckon about 40mm also

                          Sent from my SM-G970F using Tapatalk

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                            #14
                            Originally posted by Greg Rust View Post
                            Not really but letís work it out so we can solve this. The total volume of the MS isnít displaced each time you apply as the system is closed. Itís actually the ratio of the MS to the caliper that provides the increased force.
                            To be precise, we are talking about the ratio of the area of the master cylinder piston to the combined areas of the caliper pistons. A bigger master cylinder area displaces (pushes) more fluid for the same pedal stroke, and exerts less pressure. Conversely, a bigger master cylinder diameter for the same piston area will have a shorter pedal stroke.

                            That's the technical explanation, the non technical explanation is what 36 said. Have a look at the diameter of the master cylinder from the original vehicle the calipers came off, that would be your guide for the starting point for the master cylinder diameter for your car. I expect it will be bigger than what you have now.

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                              #15
                              Originally posted by Sprinkles View Post
                              To be precise, we are talking about the ratio of the area of the master cylinder piston to the combined areas of the caliper pistons. A bigger master cylinder area displaces (pushes) more fluid for the same pedal stroke, and exerts less pressure. Conversely, a bigger master cylinder diameter for the same piston area will have a shorter pedal stroke.

                              That's the technical explanation, the non technical explanation is what 36 said. Have a look at the diameter of the master cylinder from the original vehicle the calipers came off, that would be your guide for the starting point for the master cylinder diameter for your car. I expect it will be bigger than what you have now.
                              jeep is 1" or 1 1/8th depending on year so bigger than the original falcon one.

                              Sent from my SM-G970F using Tapatalk

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