Announcement

Collapse
No announcement yet.

Info on brake metering and proportioning valves

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • #16
    quote:Originally posted by WCP

    On my Avanti Turner conversion, I'm using 1&1/32" dual MC, and 13/16" rear wheel cylinders with the non-energizing stock setup and no proportioning valve. This is to maintain original design clamping balance. I'm pleased with the performance to date. You used to be able to acquire piston and seal kits for cylinders bored out to 13/16". Haven't checked lately.
    Please don't think I've being facetious with these questions. I'm truly looking for information.

    What calculations did you do to determine that you can use a bigger bore M/C, bigger bore rear wheel cylinders, and stock front caliper pistons and have a balanced system?

    You say you didn't use a proportioning valve, but did you use an external metering valve and/or residual check valve(s), OR did the M/C you selected have either one of these or both.

    If residual check valves were used, what pressure front and rear?

    You say you are pleased with the results. What occurs in a full on emergency stop from 60-70 MPH?

    What was the stopping distance before the modifications from 60-70 and what is the stopping distance now?

    Thanks.


    Dick Steinkamp
    Bellingham, WA

    [IMG][/IMG]

    Dick Steinkamp
    Bellingham, WA

    Comment


    • #17
      quote:Originally posted by Dick Steinkamp

      quote:Originally posted by WCP

      On my Avanti Turner conversion, I'm using 1&1/32" dual MC, and 13/16" rear wheel cylinders with the non-energizing stock setup and no proportioning valve. This is to maintain original design clamping balance. I'm pleased with the performance to date. You used to be able to acquire piston and seal kits for cylinders bored out to 13/16". Haven't checked lately.
      Please don't think I've being facetious with these questions. I'm truly looking for information.

      What calculations did you do to determine that you can use a bigger bore M/C, bigger bore rear wheel cylinders, and stock front caliper pistons and have a balanced system?

      You say you didn't use a proportioning valve, but did you use an external metering valve and/or residual check valve(s), OR did the M/C you selected have either one of these or both.

      If residual check valves were used, what pressure front and rear?

      You say you are pleased with the results. What occurs in a full on emergency stop from 60-70 MPH?

      What was the stopping distance before the modifications from 60-70 and what is the stopping distance now?

      Thanks.


      Dick Steinkamp
      Bellingham, WA

      [IMG][/IMG]

      Dick--

      I went with Corvette discs front and rear and a dual master (Mitsubishi--because it FIT) with a 7/8" bore. I removed the residual pressure valves from the master and installed 2# valves front and rear (Wilwood). I am running no booster. Pedal feel is solid and since I've only driven the car about 100 yards I really can't comment. I decided that it would be FAR easier to make the system work with discs on all four corners than try to use the stock brakes in the rear. Time will tell.

      Again, if I had been able to put my hands on a complete Hawk finned drum setup for a reasonable price I would have done that--it would be more "correct" for the car. But at OVER $1000 for the parts alone, I just couldn't do it. The Corvette discs and calipers were LESS!

      Comment


      • #18
        Dick, on the Turner conversion, I'm using Delco calipers with an estimated bore of 2&3/8" vs the stock 2&1/8" Stude cylinders. That results in a 25% increase in pressure area. Since the floating caliper is not as effective as an opposing piston setup, as evidenced by the lower wear on the outer pads, I estimated the increase in clamping force to be only 20% greater. By using 13/16" vs 3/4" rear cylinders, I've increased the rear cyl. area and hence clamping force 17%. If anything I'm erring on the safe side. I chose the smaller bore MC (1&1/32" vs 1&1/8") to increase line pressure with reduced pedal effort wth slightly more pedal travel. My comparisons are purely subjective. I've never been happy with Stude braking performance. My Hawk that I had for many years was terrible for brake fade. Scary! I've never been comfortable with any Avantis that I have driven, with stock brakes. My references are 2 Delco equipped disk/drum autos that I drove over many many miles - a'76 Cherokee and a '73 Chev Biscayne wagon. Those vehicles would "stand on their nose" in a panic braking situation. My current Avanti now has that braking feel. I have had a couple hard braking stops over the 4000 miles that I've logged so far, but not from 70 mph. No evidence of backend lockup. The braking response is more in keeping with the aforementioned vehicles and our 4 disk Subaru, although the Subaru should out-brake the Avanti. I did consider 7/8" cyl. for the rear, but ruled that out as it would probably result in lockup without a prop. valve.

        Comment


        • #19
          There are two areas of this discussion that, so far, have been left out. All this talk about front/rear weight distribution with no mention of trucks really makes me wonder if maybe important considerations are being overlooked. If there was really a problem with rear brakes locking up and causing dangerous drifting conditions, I think truck manufacterers would have addressed the issue, besides Fiat, by now. Fiat uses a rear brake anti lockup valve that lowers rear pressure based on the increasing distance from the axle to the frame. Why not utilize this simple technology on each individual wheel?

          Comment


          • #20

            What calculations did you do to determine that you can use a bigger bore M/C, bigger bore rear wheel cylinders, and stock front caliper pistons and have a balanced system?


            Dick Steinkamp

            [/quote]

            Here is a site that provides some insight into the calculations for disc brakes. I intend to search further to see what I can come up with concerning rear drum brakes.

            http://www.pelicanparts.com/techarti...rake_calc2.htm

            Comment


            • #21
              I've been looking but cannot find the answer to a question about rear drum brakes. How does one calculate the force exerted by the pistons in a wheel cylinder? Do you just use the cylinder bore or is the fact that there are two pistons being acted on change the way it is calculated?

              Comment


              • #22
                This is yet another reason I used front and rear brakes from the SAME
                car, and not a mixture of calipers, rotors and years. Obviously since
                there are Mustangs on the road that "stops quicker and truer" then any
                Studebaker ever made, its been proven.

                I posted my 60-0 stopping distances already, this was with the GT and
                not the larger 13" Cobra brakes. Once I get the rear matching Cobra
                brakes on the Avanti (this year hopefully) I will borrow the Gtech and
                do some more brake tests. Probably even video tape it and put it on
                my Youtube. During my testing, which was a number of HARD stops, the
                Mustang brakes never faded.

                You can see a normal stop in this "driving around" video (1:21) :

                http://www.youtube.com/watch?v=xMZ_MObo7DA

                During my initial research I didnt find that the Mustang used any type
                of factory proportioning valve, recently someone claimed it did. I did
                not notice any out of the ordinary locking of the rear wheels during a
                panic stop during my testing. The rear WILL lock before the front. My
                '60 Hawk was prone to locking the rears with its 4 wheel drum. Its due
                to weight shifting onto the front wheels during a stop. As far as the
                drum/drum debate .. I remember coming down the 154 into Santa Barbara
                in the Hawk pushing with all I could muster to get the Hawk to stop. I
                felt brake fade quite often in even regular traffic. That was back a
                few years, it would be MUCH worse today with all the extra traffic. The
                debate is silly really, what Studebaker put on their cars were good at
                the time they were used, ONLY because all the other cars on the road
                had the same handicapp. Its the same as with a non-synchro first gear.
                Not having much luck finding stopping distances for drum/drum cars. It
                seems they just tested "Coasting" back then.

                http://www.ncsdc.com/TechnicalPages/...ers/1961RT.htm

                Tom

                '63 Avanti, zinc plated drilled & slotted 03 Mustang Cobra 13" front disc/98 GT rear brakes, 03 Cobra 17" wheels, GM alt, 97 Z28 leather seats, soon: TKO 5-spd, Ported heads w/SST full flow valves, 'R3' 276 cam, Edelbrock AFB Carb, GM HEI distributor, 8.8mm plug wires
                '63 Avanti R1, '03 Mustang Cobra 13" front disc/98 GT rear brakes, 03 Cobra 17" wheels, GM alt, 97 Z28 leather seats, TKO 5-spd, Ported heads w/SST full flow valves.
                Check out my disc brake adapters to install 1994-2004 Mustang disc brakes on your Studebaker!!
                http://forum.studebakerdriversclub.c...bracket-update
                I have also written many TECH how to articles, do a search for my Forum name to find them

                Comment


                • #23
                  To the best of my knowledge; [u]no</u> regular production car with 4 wheel disc brakes even used a proportioning valve----------some disc front/rear drum cars did not use that valve either as OEM.

                  -------------------------------------------------------------------------
                  Borrowed Bams50's sigline here:

                  "Do they all not, by mere virtue of having survived as relics of a bygone era, amass a level of respect perhaps not accorded to them when they were new?"
                  --------------------------------------

                  Sold my 1962; Studeless at the moment

                  Borrowed Bams50's sigline here:

                  "Do they all not, by mere virtue of having survived as relics of a bygone era, amass a level of respect perhaps not accorded to them when they were new?"

                  Comment


                  • #24
                    quote:Originally posted by 1962larksedan
                    To the best of my knowledge; [u]no</u> regular production car with 4 wheel disc brakes even used a proportioning valve----------some disc front/rear drum cars did not use that valve either as OEM.
                    Thats true of an adjustable one, but fixed ones do exist. The Impala
                    SS in 1994-96 has 4 wheel disc and its common to mod the OEM valve to
                    allow the rear brakes to "wake up".

                    http://www.powerperformancemotorspor...productId=1749

                    Impala SS/Caprice 9C1 Stealth Brake Bolt Proportioning Mod

                    The Stealth Brake Bolt mod is a modification to the brake combination valve (combi valve) that increases the hydraulic pressure available to the rear brakes and results in less brake dive, more even brake pad wear, and slightly firmer pedal feel.

                    GM installed the same brake combination valve in the Impala SS that they used in the Caprice with rear drum brakes. Because of functional differences between drum and disk brakes, cars with rear drums use a device which delays the onset of braking to the drums as well as reducing the pressure to the rear calipers. Because the Impala was made in such small numbers, GM didn't bother to design a specific proportioning valve for the SS. Thus, the Impala exhibits excessive brake dive (the nose dips) under heavy braking and the front pads wear out quickly. The rear pads last practically forever, since they are essentially just along for the ride.

                    This Stealth Brake Bolt changes your brake pressure from est. 95% front/5% rear to 65% front/35% rear. It comes with an O-ring, instructions, and is made from high quality aluminum in the USA!


                    '63 Avanti R1, '03 Mustang Cobra 13" front disc/98 GT rear brakes, 03 Cobra 17" wheels, GM alt, 97 Z28 leather seats, TKO 5-spd, Ported heads w/SST full flow valves.
                    Check out my disc brake adapters to install 1994-2004 Mustang disc brakes on your Studebaker!!
                    http://forum.studebakerdriversclub.c...bracket-update
                    I have also written many TECH how to articles, do a search for my Forum name to find them

                    Comment


                    • #25
                      Thanks WCP for the explanation.

                      My experience with stock Stude brakes has been the opposite. I have owned several cars with stock 54 and up V8 drum/drum and disc/drum. When serviced correctly, I love the pedal feel (especially the under floor m/c cars) and the stopping ability. At South Bend in 07 I made 10+ quarter mile passes with my Corvette powered Starliner with stock '54 drum brakes in fairly quick succession. Stops were from near 100 MPH. Little to no fade...straight and true. I have heard stories like yours about "lousy brakes", but I have not experienced it in the 30+ Studes I've owned...IF the brake system was in good shape.

                      I like Tom and Allens idea of replacing the ENTIRE brake system with that of a similar weight car (if you are going to do anything). That just makes a lot of sense compared to piecing something together with "best guesses" that it will end up working acceptably as a system.

                      Lastly, I'd REALLY like to see some comparison data. Before and after and/or two similar cars stopping against eachother...one with a modified system and one with a stock system. I think we can theorize about what would be better, but it would be great to have the facts [^]

                      Dick Steinkamp
                      Bellingham, WA

                      [IMG][/IMG]

                      Dick Steinkamp
                      Bellingham, WA

                      Comment


                      • #26
                        My 53 has front discs off a 70 Nova SS and rear drums off of an 85 Monte Carlo. The brakes are quite touchy if you are not careful. I think the rears need to be backed off a bit. I have an adjustable prop valve that I plan to install to get the balance better.
                        Denny L

                        Comment


                        • #27
                          quote:Originally posted by buddymander

                          There are two areas of this discussion that, so far, have been left out. All this talk about front/rear weight distribution with no mention of trucks really makes me wonder if maybe important considerations are being overlooked. If there was really a problem with rear brakes locking up and causing dangerous drifting conditions, I think truck manufacterers would have addressed the issue, besides Fiat, by now. Fiat uses a rear brake anti lockup valve that lowers rear pressure based on the increasing distance from the axle to the frame. Why not utilize this simple technology on each individual wheel?
                          Volkswagen uses a similar prop valve setup (maybe the same one?) although I don't know if they still use it now that ABS is standard equipment. I can tell you that high speed braking gets pretty scary if that valve is frozen in the wrong position!

                          nate

                          --
                          55 Commander Starlight
                          http://members.cox.net/njnagel
                          --
                          55 Commander Starlight
                          http://members.cox.net/njnagel

                          Comment


                          • #28
                            Hi everyone
                            I have been reading this topic with interest. (see my brake mods elsewhere on this site or on Bob Johnstone's site.)
                            There is sufficient evidence here to prove that Willwood are wasting their time with disc brakes.
                            Jokes aside nobody can argue that a properly designed all disc or disc/drum system is not better than all drums.
                            The difficulty is in achieving it. The "brakemans" article is generally talking about cars with mastervac power boosted systems. That is a dual master cyl on the output side of the booster. So remember that a Hawk or any other car with an under floor M/C is a unique setup. The best safety improvement is the addition of a dual circuit M/C. Here in Australia it was "law" to have one of these from the late 60's. So must have number 1 is a dual circuit. If you wish to go 4 wheel UN boosted discs, -- easy. If you want to boost the system then you have a problem, you need 2 boosters to maintain 2 circuits. So that means pendulum pedals and a mastervac system.-- too hard. next option is front discs rear drums. This is by far the best option for a hawk. After all this is what Studebaker did.
                            In fact many commercial (large 4WD utilities) vehicles now use drum/disc combinations. The under floor M/C acts as a proportioning valve by sending normal pressure to the rear brakes and then to the booster to operate the front discs. All you need to do is get the cylinder sizing right and that is not hard.
                            There is NO NEED for a proportioning valve. Nor is there a need for a hold off valve, there is an inherent delay in the front boosted brakes to take care of nose dive. Proportioning valves were invented to reduce pressure to the rear brakes on a mastervac system because it boosts both circuits. You cannot just use any proportioning valve, they are all designed for a particular brake system and they are all different. Here in Australia adjustable proportioning valves are not street legal so you cannot use them on a registered car. They are considered a band-aid for an improperly designed system.
                            Remember, do the research, do the maths, do the mods, design into your system the ability "tweak". for example design for reducing the rear wheel cylinder size to change the balance if you have to. "Do it but do it right" The only future mod that I may do is a load sensing valve on the rear druns to counter weight transfer. But a Hawk does not greatly suffer from this problem as much as other cars.
                            My Hawk stops better, more consistently, and with much better feel.

                            Allan Tyler Melbourne Australia

                            Comment


                            • #29
                              Side note here:

                              Dual master cylinders became mandatory here in the USA starting for the 1967 model year. I am guessing that Aussie law was the same in that regard.

                              -------------------------------------------------------------------------
                              Borrowed Bams50's sigline here:

                              "Do they all not, by mere virtue of having survived as relics of a bygone era, amass a level of respect perhaps not accorded to them when they were new?"
                              --------------------------------------

                              Sold my 1962; Studeless at the moment

                              Borrowed Bams50's sigline here:

                              "Do they all not, by mere virtue of having survived as relics of a bygone era, amass a level of respect perhaps not accorded to them when they were new?"

                              Comment


                              • #30
                                I posed this question recently here on the forum, and also emailed "The Brake Man". He was courteous enough to respond, and I include his response following my question in blue.


                                quote:
                                --------------------------------------------------------------------------------
                                I have a question: Am I wrong to think that chart 3 would be the same if you used the same size front caliper and rotor on the rear, i.e. front and rear setups are equal, and used a proportioning valve on the rear?
                                --------------------------------------------------------------------------------




                                From "The Brake Man":

                                quote:
                                --------------------------------------------------------------------------------
                                Gene,
                                Brake torque is a function of piston size times line pressure. Also affecting this value to some degree is coefficient of friction of the pad and rotor size.
                                So in this theoretical, if the front and rear calipers have the same piston size, line pressure, and brake pad; then the lines on the graph would be identical.
                                If you installed a proportioning valve like you stated, and decreased rear line pressure, the the rear torque would drop as a result of the decreased pressure.
                                Which would, as you correctly assumed, make chart 3 correct for this theoretical [with the rear brake line moving up or down the graph depending on how much you reduced the line pressure with the prop valve].

                                I am assuming in the above a stock type master cylinder with only one bore for the front and rear. Master cylinder bore size dictates the line pressure developed. On some race application with both a front and rear master cylinder, two separate bore sizes will be used to achieve the desired brake torque front and rear.

                                Feel free to contact me at any time with any further question you may have about our articles or brake systems in general.

                                --------------------------------------------------------------------------------




                                I found it surprising that he would take time to answer my question, he is of a dying breed of those that are both knowledgeable and kind.


                                1963 Studebaker Avanti: C4 Corvette narrowed front/rear suspension, C5 13" calipers/rotors adapted to C4, Viper differential with Intrax 3.54 ratio (the snake has been charmed!), coil overs, stainless tubular frame, stainless chambered side exhaust.
                                Here are two links for some pictures and information.
                                Slide Show
                                Magazine Article
                                sigpic 1963 Studebaker Avanti: LS1 motor and T-56 transmission have been moved rearward, set up as a two seat coupe with independent rear suspension. Complex solutions for nonexistant problems.

                                Comment

                                Working...
                                X