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Brake master cylinder options -adjustable bias ?

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  • Brake master cylinder options -adjustable bias ?

    Hi guys,

    until now i knew we could use a Z32 BMC, so that is what i did when my brake pedal was all mushy. I cant remember, but i think the one i removed was a bm44 . Yet all the info i can find on the oem BMC of an S13 is a BM38 ? I am using an euro S13 that came with 280mm brakes as oem, so maybe we did not get the same.

    My brake setup is 330x32mm front with wilwood 4 pistons calipers and polymatrix B pads , and Z32 rear with endless pads. My BMC is a Z32 BM57 , 17/16" . And it is too big, as you may know; i have no brake feeling.

    So,i am going to change it AGAIN. On my last trackday, i noticed i locked the rear before the front, again (i also did on the previous one, so i binned the EBC yellowstuff and went back to disc eating polymatrix B).

    I am looking to kill 2 birds in 1 stone, by finding a smaller BMC with an adjustable bias.

    So, question : does it exist ? I think i will go with a bm50 (1") but i am open to suggestions.

  • #2
    Wilwood has a selection tandem cylinders in 7/8" and 1" diameter that can be used with an external proportioning valve.


    • #3
      First thing, what size pistons are on your front caliper?
      '18 Chevrolet Volt - Electric fun hatch for DD duty!

      DefSport Koni Sleeve and Spring Perch Buy!!!


      • #4
        Unfamiliar with any master cylinder with an adjustable proportioning valve.

        They sell them that you plumb in yourself.

        There has been talk about removing/disabling the stock prop valve and using an aftermarket. I believe the prop valve on s14's are threaded into the rear port on the master cylinder and someone here disabled it.

        S13's and the z32's, as far as I can tell, all have an internal prop valve that I have not seen anyone describe disabling.

        It is on my to-do list unless I throw in the pedal box I just got.

        You could just leave your master alone and throw in a prop valve after in the rear circuit, but you'll have two prop valves and two knee points where rear pressure starts to grow slower then the front. Plenty of people will say that's a huge nono. But I'd be very surprised if it didn't help a lot.

        Perhaps there is an aftermarket master cylinder that can be fitted in the stock location, using the booster, and allowing a proper install of an adjustable prop valve....


        • #5
          I haven't seen anybody describe disabling the internal prop valve either, but I think taking the spring out will do it. I need to get some brake pressure gauges to verify, but putting an inline prop valve to the rear circuit is cake at that point. Another option is to tee off a front circuit if you can't disable the rear circuit. I don't think the danger in doing that is too significant, as you're going to be in bad shape when you get a brake leak on track anyway. The failure modes all look pretty bad.
          '18 Chevrolet Volt - Electric fun hatch for DD duty!

          DefSport Koni Sleeve and Spring Perch Buy!!!


          • #6
            Cant remember the piston size, i will have to measure them. Based on their list and my brake rotor size, they could be anywhere between 1.88" and 1.38", which does not help much.

            I am not too keen on buying a wilwood BMC if i can get a solution with an easy to fit and cheap nissan BMC.

            So my current best bet would be to get a BM44 or BM50 bmc, disable the internal valve and add an inline one.

            Def > If you plan to check this in the next few weeks, please keep me updated. I'd rather drive the car this summer, could not last year, so i think for now i will just get "worse" pads for the rear.


            • #7
              Since you're planning on putting an adjustable prop valve in, I would put it in now. Unless you're tearing apart your bmc now, putting the prop valve in will make a huge difference and was going to happen anyway.

              A wilwood master cyl can be had for $90. About the same or cheaper than a Nissan part.


              • #8
                The one on the link was more like 260$ (+shipping and customs). The nissan part is really bolt on though, and i am growing everly tired of adapting items. Even more when there is an easy, no mod solution.

                I will change the BMC and put the propvalve at the same time, just not right now. If i can get a balanced braking by just changing the pads, i will just have to change the BMC for a smaller one.