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Disk Brake Conversion Discussion

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  • Originally posted by jopizz View Post

    You can change the master cylinder to a dual for drum brakes but the under dash booster will never work for disc brakes. It's woefully inadequate.

    John
    What is the difference(s) in line pressure regarding the BENDIX as compared to the KH?

    Comment


    • Kultulz raises a great question, one that has been on my mind for a long time. For the answer, I called Booster Dewey because he has loads of experience and he knows his stuff.

      He and I grew up together and have many parallel lines in our lives. He's also a great guy who loves his work and is eager to answer any booster questions (503-238-8882 in Portland, OR).

      The question is, is there a site that shows real outputs for any size booster? The answer is emphatically, no, because there are too many variables, even in the same car.

      Booster output depends on foot pedal pressure, vacuum pressure, and the size & design of the booster. We don't always apply the same foot pressure, but we compensate for all the other variables by only using enough pressure to stop in the correct distance. That happens by 'second nature' as your brain adds up all your senses.

      Dewey tells me that there were over fifty different designs for the same size boosters from different manufacturers. They all had different characteristics and the only way to measure comparisons is in a very controlled test. Your car doesn't operate in a lab.

      So, sometimes your engine produces more vacuum than at other times; it fluctuates but the check valve will pass any vacuum that is higher than presently in the reservoir. That alters the output for the same foot pressure. Then, the rest of the system plays an important role such as mechanical adjustments, brake fluid condition and the presence of air, temp and humidity, pads or shoes size (it changes), size of M/C bore, speed of the car, how long the brakes are applied, etc., etc.

      The closest explanation I found on the net is, "the booster amplifies the foot pressure two-to-four times." (great!) MBM says, "Typically you should expect about 1000 psi to the wheels for a disc brake system. A disc brake system requires this amount of pressure so be careful when using a smaller 7" booster that puts out only 900 psi pressure." They are talking about DUAL DIAPHRAGM boosters. That's why I use dual diaphragm 8" boosters. - Dave
      My latest project:
      CLICK HERE to see my custom hydraulic roller 390 FE build.

      "We've got to pause and ask ourselves: How much clean air do we need?"
      --Lee Iacocca

      From: Royal Oak, Michigan

      Comment


      • Another factor is pedal ratio and that ratio is probably different between the Bendix and Kelsey Hayes styles. I remember trying to figure all that out 10 years ago when I converted mine to discs however I have the Bendix under the hood style booster.

        Booster Dewey rebuilt and converted my booster so that I could run a modern disc/drum style master cyl. The conversion is simply a change of the face of the booster to a '61-'63 Lincoln style with 2 larger studs from the 4 small stud style that was standard on the Bendix booster.

        Something to keep in mind is that if you add a disc or drum master cyl on the firewall in the engine compartment of the Kelsey Hayes under dash system you'll need to drill new holes to adapt the modern 2 bolt style master cyl then try to figure out the right length master cyl push rod to make it work with the old Kelsy Hayes under dash booster.

        Good luck,
        Eric

        Comment


        • Originally posted by simplyconnected View Post

          The closest explanation I found on the net is, "the booster amplifies the foot pressure two-to-four times." (great!) MBM says, "Typically you should expect about 1000 psi to the wheels for a disc brake system. A disc brake system requires this amount of pressure so be careful when using a smaller 7" booster that puts out only 900 psi pressure." They are talking about DUAL DIAPHRAGM boosters. That's why I use dual diaphragm 8" boosters. - Dave
          My contention is that the KH Booster will give greater application pressure as opposed to manual Disc/Drum. It may or may not deliver as much force as a BENDIX setup of the period (line pressure being determined with gauges). The MC design is the more important factor.

          The principle of operation is the same, the only difference being a remote vacuum chamber.

          Comment


          • However you get 1,000psi to the wheel cylinders, whether it's from one company or another, as long as it's there when you need it IS the bottom line.

            My worry for disk brake retrofits is that your system may be underpowered. The original Squarebird brake system was grossly underpowered from the factory. There is NO reason why your classic car should have inferior brakes compared to modern cars because we have the technology and parts.

            We rarely use full foot pressure. Simply because the booster stops the car doesn't mean it's going to deliver enough for a panic stop. Boosters put out only so much assistance, then the rest is up to your foot. Most 16 yr-old girls don't have enough strength, but they shouldn't need it. After all, these are POWER BRAKES. Better to be over-assisted than underpowered. - Dave
            My latest project:
            CLICK HERE to see my custom hydraulic roller 390 FE build.

            "We've got to pause and ask ourselves: How much clean air do we need?"
            --Lee Iacocca

            From: Royal Oak, Michigan

            Comment


            • Originally posted by KULTULZ View Post
              What is the difference(s) in line pressure regarding the BENDIX as compared to the KH?

              this is a great question... I saw some manual M/C disc conversion kit . I suppose they work although the driver needs to make enough foot pressure to stop the car, this is why I asked about a conversion with a working K/H booster in its place. It should be something better than nothing . But John says it does not work because the disc brake need considerably higher pressure than drums
              Lake cruisers

              Comment


              • Originally posted by sunnybob View Post

                this is a great question... I saw some manual M/C disc conversion kit . I suppose they work although the driver needs to make enough foot pressure to stop the car, this is why I asked about a conversion with a working K/H booster in its place. It should be something better than nothing .

                But John says it does not work because the disc brake need considerably higher pressure than drums
                Actual line pressure has much to do with the MC selection and brake pedal leverage as well as booster style and diaphragm size. GOOGLE and study different types of MC.

                We do not know if FORD went away from the KH design to the BENDIX design either by function and/or cost. One would actually have to do an in-depth conversion to know what will and won't work.

                To me, even if it gave minimal increased performance (car originally built with the KH System over a manual disc/drum conversion, it would be worth it just for aesthetics, but then again, I am anal. I like the idea of not seeing a booster (especially a dual diaph./GM MC) under the hood of a well detailed engine.

                Comment


                • Other question:

                  Is there a list of extra parts (like hoses, bearings ecc) I would need if I will buy scarebird adapter?

                  I saw there is a well done part list for Hotrods kits but I can't find what rotors and caliper are used in their kits.

                  Thanks. Sorry for all my questions.. I'm going to understand which upgrade kit will fit better my Tbird and my wallet (shipping overseas is very expensive )
                  Lake cruisers

                  Comment


                  • Granada spindle problem

                    Yet another reason to re-consider using the Granada spindle conversion.

                    The drivers side on my conversion has always scraped in a right hand turn. Looked when I first completed the conversion but didn't really see anything. Sounded like the rotor was scraping against something - not real bad but just annoying. I always figured it was the bottom back angled edge of the A-arm pushing the backing plate into the rotor. That was sort of right.

                    Since I replaced the engine and have the car back on the road I decided there would be enough wear by now to see what the noise was.

                    Apparently the geometry is such that in a right turn when the car is leaning and you are braking (compressing the front suspension) the spindle moves enough for the outside edge of the A-arm to push the backing plate into the rotor (or it may just be the difference in geometry). There is about 1 1/2 distance between the lower edge of the A-arm and the rotor in the static or resting state of the suspension so initial clearance is not a problem. All bushings, tie rods, ball joints, sway bar links etc are new. May be doing the same thing on the passenger side but I haven't noticed it - might be because it's on the far side of the car and I just don't hear it.

                    Removed the lower ball joint (has less than 5k miles on it) and it still seems tight but I plan on replacing it just to see if that makes a difference.

                    You can see the oval rub mark in this pic where the A-arm is pushing the backing plate into the rotor.



                    Here is an old pic showing how the geometry is changed.
                    Basically the Granada spindle sits higher on the lower ball joint.

                    Red vertical line is an imaginary line through center of the upper and lower ball joints, Horizontal red line is an imaginary line through the center of the axle and yellow horizontal line is a 90 deg imaginary line through the center of the spindle where it connects to the bottom ball joint showing the difference in axle angle and height.



                    (the '77 Tbird spindles have a geometry closer to the Tbird but I tried those and they have way too much positive camber (blue line) to adjust out - the car won't align)

                    Just some fyi,
                    Eric

                    Comment


                    • Disk Brake Conversion Discussion

                      Thanks for this post, Eric. This information is good to know for people who are considering going the Granada route....

                      Ray Clark - Squarebirds Administrator
                      The Terminator.....
                      Contact me via Private Message for my email address, or Call (Cell) 210-875-1411

                      https://www.squarebirds.org/picture_gallery/TechnicalResourceLibrary/trl.htm

                      Comment


                      • Eric, have you ever had somebody crank the steering from static to hard right turn position while you watched the bottom arm/back-plate area to see how much movement is taking place?

                        And then had another person 'bounce' the suspension on that side to simulate braking while turning?

                        It's just that in my eyes that seems to be an awful lot of unwanted movement.
                        A Thunderbirder from the Land of the Long White Cloud.

                        Comment


                        • compare

                          Eric shoot me an email if you want any comparison photos or measurements from my Versailles set up.
                          Because of your cautionary words I made a spindle centric table to do a spindle comparison before proceeding. I don't think the spindle sits higher on the ball joint because if it did you couldn't get the castle nut and cotter key to work. The original spindle had a thicker arm so the lower surface of the arm was lower on the ball joint compressing the grease boot. I still have an original spindle set if we need them for measurements also.
                          Grant
                          Grant
                          NCbird on the Coast of NC
                          "Dads Bird" for my father

                          Comment


                          • Replaced my lower ball joint but of course it was raining when I finished so I didn't want to do a test drive.

                            Here is the clearance full left turn - the rotor doesn't rub on a left turn. (viewed from the front)


                            Here is the clearance centered (viewed from the front)


                            then clearance full right turn - where it normally rubs in a hard turn. I don't see a noticeable difference in clearance between the old and new ball joint. (viewed from the back)
                            The test will be driving it I guess.


                            (may be hard to tell but clearance is about the same in all positions - more in the first pic but by only a little bit)

                            Grant - is your car on the road? Curious if yours is not rubbing what the difference is. Thought the Versailles and Granada spindles were the same. You are probably right about the spindle placement - it may just be the difference in the bottom thickness. My Granada spindle does sit pretty low on the Tbird joint because the hole for the cotter pin is almost too high. I use a washer between the castle nut and spindle so that the nut and cotter pin are lined up normally. That could mean that the shop that modified my lower spindle hole to accept the Tbird ball joint could have gone a bit far but both sides are the same. They are a reputable shop and supposedly made the modification before. It may also be the alignment that is causing the rubbing. There are more spacers on the upper A-arm than with the original A-arm. Still planning on getting those settings and posting because the car drives so nice and feels very stable.

                            Tom - haven't found any one brave enough to sit on the front fender and look while I'm driving along - heh. That's a good idea - not sure one person could bounce it hard enough but it's worth a try - it only rubs in a pretty hard cornering situation.
                            I could turn it into a right turn and put the spring on a stand then spin the wheel. If it rubs when I bounce it that would tell me it's just the geometry of the Granada spindle on the Tbird suspension and not movement of the ball joint - yes that's worth a try.

                            Thanks,
                            Eric

                            Comment


                            • Originally posted by DKheld View Post
                              ...Thought the Versailles and Granada spindles were the same. ...My Granada spindle does sit pretty low on the Tbird joint because the hole for the cotter pin is almost too high. I use a washer between the castle nut and spindle so that the nut and cotter pin are lined up normally. That could mean that the shop that modified my lower spindle hole to accept the Tbird ball joint could have gone a bit far but both sides are the same...
                              Eric, I think you're on to something here. The difference between Granada and Versailles is that the bottom hole is already reamed for large size ball joints in the Lincoln spindle. That's the only difference.

                              Your shop may have cocked the reamer as they over drilled this tapered hole. Ball joints tend to take up any deviation because they swivel. That doesn't mean the new hole isn't closer to your lower "A" arm...

                              I reamed my own holes in my Granada spindles, and they turned out perfect. I used a good drill press but I can easily see how someone could make the angle different. These spindles are soft steel and easy to machine. - Dave
                              My latest project:
                              CLICK HERE to see my custom hydraulic roller 390 FE build.

                              "We've got to pause and ask ourselves: How much clean air do we need?"
                              --Lee Iacocca

                              From: Royal Oak, Michigan

                              Comment


                              • off road

                                Eric, I am not on the road yet so can't answer the rub question. Hope to wrap up my work under the car soon. Finished headers, sway bars, new fuel n brake lines just have new tank left. My spindle arm did not require any spacers top or bottom. The castle nut/cotter key aligned the way I would expect. Based on your input I specifically only wanted Versailles spindles. That said my clearance looks just like yours. Grant
                                Grant
                                NCbird on the Coast of NC
                                "Dads Bird" for my father

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