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Which BMC for S14 w/ 350z Brembos?

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  • Which BMC for S14 w/ 350z Brembos?

    Hello mates! I can see that some of you fellas have first hand experience with these types of questions, and hopefully someone can chime in and recommend me a BMC to use with my setup.
    Any and ALL advice will be greatly appreciated!

    Let me make this as short as I can without skipping important details.

    I have some 350z Brembo front calipers that I got for cheap.
    Currently im using Z32 fronts on my S14 with OEM rear and they have worked ok for the last 8 years, but I want something different now for both performance and looks ()

    I have 2 options for the BMC that I think will work: the BM44 (15/16) and the BM50 (1"). I have the manual no abs small brake booster so anything after the 1" BMC might be too stiff.

    The Brembos don't have a ton more torque than the Z32 fronts, but the bigger rotor and brake pad adds up to quite a bit more overall.

    I will keep the S14 rears and will be using a Fastbrakes 12.3" rear kit, and after some max brake torque math they came out to 70/30 brake distribution w/ the 350z Fronts.

    I haven't added any more pistons to my setup, just bigger ones up front and I want something that won't lock up too easily and I also don't want something that will be too stiff and hard to stop.

    I want to keep the small manual S14 BMC because it clears my turbo well.

    Thanks of you managed to read this far! And again fellas, THANKS for any advice/info.

  • #2
    And BTW:

    The 15/16 is from a 1984 NA Z31, and the BM50 1" is from a 1993 Q45 <-- Both have the same 569psi split point and reducing ration as the JDM S14/S13 BMCs.

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    • #3
      Seems front biased, I'd shim the prop. valve up to get the bias back to something more reasonable.

      As far as BMC size - what's the total piston area vs. the total piston area of Z32 fronts and rears? That should tell you how a 1" BMC will feel pedal pressure wise.
      '18 Chevrolet Volt - Electric fun hatch for DD duty!


      DefSport Koni Sleeve and Spring Perch Buy!!!
      http://www.nissanroadracing.com/showthread.php?t=5902

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      • #4
        These equations are based off of the piston/pad size/effective rotor area formula that was used on this post
        :
        http://www.sr20forum.com/240sx-s13-s...ke-setups.html

        The 350z fronts on the 12.75" track rotors have 4 pistons ( 2 of them are 38mm and 2 of them are 44mm) TOTAL maximum brake torque is: 1,829,932

        The Z32 calipers are 40.5mm x 4 = 162mm total piston area per caliper, and 324mm total front.
        The 350z are 38mm x 2 and 44mm x2 = 164mm total piston area per caliper, and 328mm total front.

        ^ I hadn't realized that they were this close in total piston area!

        The S14 with single 38.1mm sliding caliper on Fastbrakes 12.3" rotors give 795,192 max torque.

        This adds to a maximum brake torque of 2,624,124

        Brake bias would be 69.7/30.3 (Front 350z/Fastbrakes 12.3" Rear)

        Im not sure if units of measuring are in lbs or something else...but I can see a lot of setups measured that way.

        And I double checked and the 300zx front and S14 rears do yield a 70.5/25.5 F/R brake bias, therefore thats why JDM S14s came with them from factory.

        If this is wrong someone correct me please.

        Thanks fellas!
        Last edited by 240sxfan6882; 10-14-2014, 03:10 PM.

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        • #5
          I did some total piston areas on each type of caliper. The Z32 uses 38.18x2 pistons, and the S14 uses a single 54mm front piston and single 38.18mm rear piston (again correct me if im wrong), but

          Total area of Z32 All around: 476.72mm
          Total area of Z32 front w/ S14 Rear Single Piston: 432mm
          Total area of Z33 front w/ S14 Rear Single Piston: 436mm

          ^ Looks like the Z33 Brembo and Z32 calipers are very very close in terms of piston area. So the added braking power comes mainly from the much larger 12.75" rotor and bigger brake pad compared to the Z32.

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          • #6
            Either 15/16 or 1" MC would be fine. If you have a small booster I'd probably lean towards the 5/16" option personally. Z32 piston area with a 1" MC and a small booster is pretty firm.
            '18 Chevrolet Volt - Electric fun hatch for DD duty!


            DefSport Koni Sleeve and Spring Perch Buy!!!
            http://www.nissanroadracing.com/showthread.php?t=5902

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            • #7
              Originally posted by Def View Post
              Either 15/16 or 1" MC would be fine. If you have a small booster I'd probably lean towards the 5/16" option personally. Z32 piston area with a 1" MC and a small booster is pretty firm.
              I was leaning on the 15/16 myself too with the manual BMC.
              However, since the S14 lines are different than the Z31 15/16 BMC, I will have to bend them.

              The BM50 from the Q45 fits and I just have to tap one port to make it work on non ABS and the stock S14 lines match up.

              The reason I don't go with an S14 15/16 BMC is that for the US models the splits points are much lower than the 569psi that all the others came in Japan.
              And no USDM S-chassi came with Z32 fronts.

              Thanks Def!!

              Comment


              • #8
                S14 has an external prop valve no? Why not just put an adjustable prop valve and tune it for your car? They're cheap, like $40-50ish.
                '18 Chevrolet Volt - Electric fun hatch for DD duty!


                DefSport Koni Sleeve and Spring Perch Buy!!!
                http://www.nissanroadracing.com/showthread.php?t=5902

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                • #9
                  Originally posted by Def View Post
                  S14 has an external prop valve no? Why not just put an adjustable prop valve and tune it for your car? They're cheap, like $40-50ish.
                  The valve is built onto the BMC, but luckily it is easily accessible from the outside:
                  http://www.nissanroadracing.com/showthread.php?t=1149

                  The proportioning valves look exactly alike on the Q45 BMC and the S14 BMC.
                  I'm thinking of switching the valves on the BMCs.
                  Mind again that the stock USDM S14 is something like 284psi split point, and the Q45 is 569psi (same as JDM).
                  I think I can just get an 15/16 S14 BMC and switch out the springs to give me the 569psi rear split point that I want.

                  I'll keep you posted!

                  Thanks a lot Def!!!!
                  Last edited by 240sxfan6882; 10-15-2014, 10:27 AM.

                  Comment


                  • #10
                    Id go adjustable valve personally. I doubt the stock split point is optimal for a lowered car with stiff suspension and far stickier tires.
                    '18 Chevrolet Volt - Electric fun hatch for DD duty!


                    DefSport Koni Sleeve and Spring Perch Buy!!!
                    http://www.nissanroadracing.com/showthread.php?t=5902

                    Comment


                    • #11
                      Originally posted by Def View Post
                      Id go adjustable valve personally. I doubt the stock split point is optimal for a lowered car with stiff suspension and far stickier tires.
                      Point taken.
                      I'll try this out for now, and down the road I will look towards bypassing it and getting an adjustable valve.

                      Thx Def

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