Brake Proportioning Valve Qusetion

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  • Chickenman
    Moderator
    • Mar 2002
    • 1396

    Brake Proportioning Valve Qusetion

    I recently installed a big brake upgrade to the Camaro. 4 Piston WilWood Superlites wih 12" x 1.375" rpotors. Everything works fine except that I have thrown the brake balance off. Waaaaayyyy too much front brake now, even with the current proportioning valve cramked all the way to full rears.

    Untill I can aford to update the rear with 4 piston Superlites, ( Currently 1LE setup with PBR calipers and 11.8" rotors ) I was thinking about just switching the Prop valve to the front brakes.

    Don't think it will be a problem, Sprint cars do it all the time, but just wondering about any thoughts on this?
  • Bigger is Better
    • Sep 2001
    • 217

    #2
    Hey Chickenman,

    First thing I would do is sell the camaro and buy a TransAm.

    A prop valve doesnt really alter a the brake balance just the rate in which pressure is applied to the brakes.

    That said I dont know if a prop valve can hide a a really large brake inbalance, particualry for a long brake application (like Knox!).

    Do you think that a 1LE master cylinder would help, you would have to do the numbers as far as the front PBR to your wilwood caliper?
    Johnny
    http://www.youtube.com/watch?v=Xc5rpSGwXlM

    Comment

    • Chickenman
      Moderator
      • Mar 2002
      • 1396

      #3
      Originally posted by Bigger is Better:
      Hey Chickenman,

      First thing I would do is sell the Camaro and buy a TransAm.

      A prop valve doesnt really alter a the brake balance just the rate in which pressure is applied to the brakes.

      That said I dont know if a prop valve can hide a a really large brake inbalance, particualry for a long brake application (like Knox!).

      Do you think that a 1LE master cylinder would help, you would have to do the numbers as far as the front PBR to your wilwood caliper?
      Re: TransAm....why would I want to go slower?

      I probably know the answer to this one myself. Prop valves can handle a fairly large brake imbalance. Most valves can reduce braking pressure to the order of 50%. You're incorrect on your premise that proportioning valves cannot alter the brake balance...that it controls the rate of pressure application only. Aftermarket valves can limit line pressure from 100 PSI to 1,000 PSI. The pressure curve will be linear up to the " Blowoff " pressure, which is usually around 1,000 PSI.

      Master Cylinder is not the problem. GM M\C bores are linear...not stepped. 1LE master cylinder is same as what I run now.

      Swept area is the main problem. Very small pads on the rear. As well the PBR rear calipers have very small cylinders, so clamping forces are reduced.

      The more I read the more I think that this will work. I'm going to test early this year. So if things don't work out I can quickly order some rear Superlite calipers and fix things properly. It's just more money that I didn't want to spend.Still have to buy tires and sort out the suspension and a few other things.

      BTW...have you even installed your WilWood Proportioning valve that was gathering dust for 5 years?

      Ready to get your butt kicked again at Knox?

      [ December 08, 2003, 11:11 AM: Message edited by: Chickenman ]

      Comment

      • Carson
        VCMC Lifeblood
        • Dec 2005
        • 5448

        #4
        Re: Brake Proportioning Valve Qusetion

        Originally posted by Chickenman
        Prop valves can handle a fairly large brake imbalance. Most valves can reduce braking pressure to the order of 50%. You're incorrect on your premise that proportioning valves cannot alter the brake balance...that it controls the rate of pressure application only. Aftermarket valves can limit line pressure from 100 PSI to 1,000 PSI. The pressure curve will be linear up to the " Blowoff " pressure, which is usually around 1,000 PSI.
        Bringing back another old thread to life, so much good info on this forum.

        Currently my civic has a braking problem, I can lockup my tires with only around 20% of pedal travel, making it quite difficult to do precise braking, there is also a bit of rear bias. Based on the post above, am a correct to think that an adjustable brake proportioning valve will allow me to reduce the braking sensitivity as well as to fix the rear bias?
        _________________
        Carson Au
        2011 Suzuki GSXR600 - Track
        2011 Triumph Speed Triple - Daily
        2001 Toyota Sienna (don't ask...)

        Comment

        • lowside67
          Senior Member
          • Mar 2007
          • 902

          #5
          Re: Brake Proportioning Valve Qusetion

          You have two problems and will need to take two steps to adequately fix them.

          Your front to rear brake bias issues can be solved by limiting the maximum brake pressure applied to the rear brakes via a proportioning valve.

          However, it will not have any meaningful effect of increasing the pedal travel to help make modulating easier. For this, you need to reduce the diameter of your master cylinder.

          When we did the 4 wheel brake swap on my Civic, I spent quite a bit of time doing homework to make sure that we ended up with a complete system that worked well - what that took in my car was front and rear DC2 integra calipers, 91 civic EX 4dr 15/16" MC, stock EG booster, and a "4040" proportioning valve which is from a non ABS DC2 Integra (RS model). With this setup, the brakes were AWESOME - modulated nicely, were well balanced front to rear, and had great feel.

          Mark
          Mark Uhlmann, UBCSCC Ex-Pres
          BM #51: 2004 Stohr WF1
          STX #67: 2011 BMW 128i (sold 2019)
          DSP #67: 1997 BMW 328is (sold 2012)

          Comment

          • Carson
            VCMC Lifeblood
            • Dec 2005
            • 5448

            #6
            Re: Brake Proportioning Valve Qusetion

            Originally posted by lowside67
            You have two problems and will need to take two steps to adequately fix them.

            Your front to rear brake bias issues can be solved by limiting the maximum brake pressure applied to the rear brakes via a proportioning valve.

            However, it will not have any meaningful effect of increasing the pedal travel to help make modulating easier. For this, you need to reduce the diameter of your master cylinder.

            Mark
            Thx Mark, when talking to you yesterday, you mentioned that you had the same problem and ended up going with a MC from another civic, which one was that?
            _________________
            Carson Au
            2011 Suzuki GSXR600 - Track
            2011 Triumph Speed Triple - Daily
            2001 Toyota Sienna (don't ask...)

            Comment

            • lowside67
              Senior Member
              • Mar 2007
              • 902

              #7
              Re: Brake Proportioning Valve Qusetion

              Added some more info to my last post.
              Mark Uhlmann, UBCSCC Ex-Pres
              BM #51: 2004 Stohr WF1
              STX #67: 2011 BMW 128i (sold 2019)
              DSP #67: 1997 BMW 328is (sold 2012)

              Comment

              • Sead
                (former) Top Gun
                • Jun 2001
                • 1887

                #8
                Re: Brake Proportioning Valve Qusetion

                I did the McGyver solution on my Scirocco:

                1. Bought the worst brake shoes I could for the rear
                2. Shaved their edges down for less surface area.

                Carson, it would like you need both a proportioning valve and duller pads on the back.

                And I gotta say, Mark's brakes in the Civic were astonishingly good on the AutoX pad.

                Comment

                • Carson
                  VCMC Lifeblood
                  • Dec 2005
                  • 5448

                  #9
                  Re: Brake Proportioning Valve Qusetion

                  Originally posted by Sead
                  Carson, it would like you need both a proportioning valve and duller pads on the back.
                  Good to know, I already have 3rd party "oem" pads, not sure if it could get duller than that, and with HP+ the front they feel pretty balanced. The prob with mixing and matching pads is that when temperature change, the balance changes too.

                  I don't know much about adjustable proportioning valves. are they universal? the ones I have seen online don't list application, do I just modify the brake lines to fit it?
                  _________________
                  Carson Au
                  2011 Suzuki GSXR600 - Track
                  2011 Triumph Speed Triple - Daily
                  2001 Toyota Sienna (don't ask...)

                  Comment

                  • lowside67
                    Senior Member
                    • Mar 2007
                    • 902

                    #10
                    Re: Brake Proportioning Valve Qusetion

                    They are universal, they get spliced into your rear brake hardlines.
                    Mark Uhlmann, UBCSCC Ex-Pres
                    BM #51: 2004 Stohr WF1
                    STX #67: 2011 BMW 128i (sold 2019)
                    DSP #67: 1997 BMW 328is (sold 2012)

                    Comment

                    • Carson
                      VCMC Lifeblood
                      • Dec 2005
                      • 5448

                      #11
                      Re: Brake Proportioning Valve Qusetion

                      thx mark, thinking of getting something like this:
                      _________________
                      Carson Au
                      2011 Suzuki GSXR600 - Track
                      2011 Triumph Speed Triple - Daily
                      2001 Toyota Sienna (don't ask...)

                      Comment

                      • Chickenman
                        Moderator
                        • Mar 2002
                        • 1396

                        #12
                        Re: Brake Proportioning Valve Qusetion

                        Originally posted by Carson
                        thx mark, thinking of getting something like this:
                        http://cgi.ebay.com/ebaymotors/NEW-W...#ht_2185wt_830
                        You don't need one that fancy. That is to replace OEM GM combo valves ( Used on older Vettes I believe ). Would be a hassle to plumb into your Civic.

                        Just buy this:



                        You might also want to check out the Wilwood lever type valve. Makes in car adjustment a lot easier.



                        BTW. Kratter is an awesome E-bay store for Wilwood Brake Parts. All new products and super prices.

                        IMPORTANT!! You have to completely remove the factory combination valve when you install an aftermarket proportioning valve. Failure to do so will result in a horribly long and soft pedal.

                        Tee the front brakes together with a brass tee fitting. Run the rear brakes from the proportioning valve to the rear brakes. If you need a hand, I have plenty of experience at this and have the necessary flaring tools and tubing cutters. Give me a call.

                        B&J parts in Port Coquitlam also has a great selection of brake adapters. Some odd ball stuff that is hard to find. IE: Pre-made lines with an SAE fitting on one end and Metric on the other. Exactly what you may need for that Wilwood valve. Much better selection than Lordco.

                        Comment

                        • Chickenman
                          Moderator
                          • Mar 2002
                          • 1396

                          #13
                          Re: Brake Proportioning Valve Qusetion

                          Carson. You got disc brakes on the rear or drum brakes?

                          Comment

                          • SkinnyG
                            MIA
                            • Jun 2001
                            • 1906

                            #14
                            Re: Brake Proportioning Valve Qusetion

                            Originally posted by Chickenman
                            IMPORTANT!! You have to completely remove the factory combination valve when you install an aftermarket proportioning valve. Failure to do so will result in a horribly long and soft pedal.

                            Tee the front brakes together with a brass tee fitting. Run the rear brakes from the proportioning valve to the rear brakes. If you need a hand, I have plenty of experience at this and have the necessary flaring tools and tubing cutters. Give me a call.
                            ^^^ This is very important. If I remember correctly, most FWD cars run a Diagonal-Split brake system (that is, RF and LR run off one cylinder of the master, the LF and RR run off the other - this provides one good front brake in the event of half system failure, as opposed to F/R split, which might leave you with only the "trunk holder upper" brakes should the fronts fail).

                            I might be way wrong, however.
                            This doesn't put food on your table, it's supposed to be fun. If you're not having fun, you're doing something wrong.
                            -=- Lethal Locost -=- Lethal Locost 2 -=- V8 Firefly -=- Crusty Chevy -=-

                            Comment

                            • Carson
                              VCMC Lifeblood
                              • Dec 2005
                              • 5448

                              #15
                              Re: Brake Proportioning Valve Qusetion

                              Originally posted by Chickenman
                              Carson. You got disc brakes on the rear or drum brakes?
                              ITR Disc brakes all around.
                              _________________
                              Carson Au
                              2011 Suzuki GSXR600 - Track
                              2011 Triumph Speed Triple - Daily
                              2001 Toyota Sienna (don't ask...)

                              Comment

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