Observations from My Disc Brake Conversion

Brakes for your Classic Mopar

  1. 1969VADart

    1969VADart FABO Gold Member FABO Gold Member

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    Well I finally got my disc brake conversion done on my 69 Dodge Dart GT. Thought I would share some pictures and observations of my project. I purchased the Pirate Jack manual disc brake kit. All things considered, I thought it was very reasonably priced. It was not missing any parts and I actually had a number of pieces of hardware left over (maybe that is bad). The components included bigger ball joints with the adapter sleeve for the factory UCAs. While others have used the locking nut for the UCA without issue, I just was not comfortable with that set up. Additionally, while one sleeve slipped into the spindle clean, one did not even fully clear the top of the spindle bore. This let me to make a major mistake that led me to ultimately purchase new tubular UCAs from PST. Despite some concerns, those tubular UCAs ended up being a good decision. I made the conversion because I was tired of the constant problems I was having with the old worn out parts particularly on the passenger side front wheel.

    Disassembly is pretty easy to do. You should decide from the beginning if you want to change UCAs or LCAs. Having a good ball joint separator/pickle fork was critical to the disassembly. Side note: the jack stands I used are not the ones that have been recalled.

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    • 1969VADart

      1969VADart FABO Gold Member FABO Gold Member

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      After my screw up with the adaptor sleeves, I broke down and spent the money for the PST tubular UCAs. Installation was not that difficult but a rubber mallet was essential to getting them into place. Also, I had to shave off the lip of the frame tab on both sides to give the tubular arms room to rotate down. A small Dremel tool was invaluable for this. I used a jack under the LCA to relieve pressure on the suspension during disassembly and to assemble the spindle on the upper ball joint rather than cranking down the torsion bars. That works fine. Some instructions recommend assembling the entire hub assembly (spindles, caliper mounts, rotor) first. I would say mount you caliper brackets on the spindle and mount, then mount rotor assembly, then calipers. Also, the instructions for the rear seal were really not that clear. The answer is the rubber lip should face out of the back of the hub towards the backing plate.

      When installing the calipers, I definitely bent the tabs down on the outer pads because they had a noticeable rattle. I installed the little rubber bands for the inner pads, but opinions vary as to whether that makes any difference. I installed the rubber hoses that came with the kit, but their length clearly was meant for front mount of the calipers and I chose rear mount. I ended up ordering hoses from Dr. Diff meant for rear mount (they are shorter).

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      • 1969VADart

        1969VADart FABO Gold Member FABO Gold Member

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        One of the hardest parts of this project was replacing the distribution block with the right proportioning valve. The kits mostly come with an adjustable valve for the rear wheels. That requires modification to the rear brake lines that I was unwilling to do. So I ordered the correct proportioning valve for a disc/drum brake system from Dr. Diff. Taking this apart and putting it together was like a jigsaw puzzle. Clearly the entire car was built around the piece already being installed. I ended up having to pull my rear brake line off the car because I couldn’t get it to seal on the new proportioning valve when I started bleeding the brakes. Turns out the flare had a burr on it. A little filing fixed the problem. That valve looks like this.

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        Bench bleeding the master cylinder was a must. It is a bit of a struggle, particularly if you don’t have a vice, but it can be done effectively on a table top if done slowly. It took about 15 minutes to be sure this was done. I installed a MC with 1 1/32” bore size. The pedal is not stiff at all after bleeding the system and feels very smooth.

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        Take it from me, once you get everything together don’t panic if the front end looks way out of alignment. My key was to get my ride height satisfactory first. I measured both off the LCA and torsion bar as well as the fender lips. The first drive I had a slight rub on the front drivers side fender. Getting the wheel to basically neutral camber and raising the car half an inch cured the problem. Here are a few initial let down and after drive pictures with some home/garage alignment. I have not had it professionally aligned yet, but the car tracks like it is on rail and drives very smooth. No wander or pull.

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        First drive pics and settling in after that drive.

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      • 1969VADart

        1969VADart FABO Gold Member FABO Gold Member

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        And here’s the stance currently after tweaking on the adjustments. Of note: both the front and rears of the UCA mounts are adjusted most all the way in to get the camber adjustment where it is now. It can probably be improved a little but the drive and handling feels excellent as it sits.

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        Last edited: Jun 22, 2020
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        • Dfr360cuda

          Dfr360cuda MAGA Again

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          I picked a good time to do my upgrade. You make like 4 guys doing this right now. Expect some questions.
          Thanx

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        • Dragonsteel

          Dragonsteel Well-Known Member

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          Looks good, but I hope your running the newer brake fluid that doesn't eat paint as those cast iron master cylinders tend to leak!
           
        • dano

          dano Evil Handy Man

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          How much does that front tire rub? That camber just doesn't look right with the full weight on the nose.
           
        • jbc426

          jbc426 Well-Known Member

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          Good for you for tackling the job. I used Dr Diff's econo 4 wheel kits to upgrade the brakes on both my Mopars. One is manual and the other power assist. They both work great, and Dr Diff is an incredible source of knowledge and advice.

          Be sure to keep an eye on the hardware and fastener tightness and consider getting a proper front end alignment with as much caster as you are able to get with the stock strut rods.

          On both my cars, I was barely able to get positive caster with the stock strut rods, because the rear end of both cars are slightly higher than the front.
           
        • 1969VADart

          1969VADart FABO Gold Member FABO Gold Member

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          Feel free to shoot me any questions.
           
        • 1969VADart

          1969VADart FABO Gold Member FABO Gold Member

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          I am running the DOT3 fluid. I painted the MC with Eastwoods Brake Gray paint because it is supposed to resist the eating up of paint by the brake fluid. I have always run DOT3 from the beginning of my build and never had a leak (knock on wood).
           
        • 1969VADart

          1969VADart FABO Gold Member FABO Gold Member

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          The last set of picks are how the car sits after about 40 miles of driving. There is absolutely no rubbing on either wheel. But I should mention that the upper part of my fender lips are rolled in a little. But otherwise at a full lock turn either direction there is no rubbing and even when the suspension cycles. The ride height is within an 1/8" of being the same on both sides (its hard to get both sides exact). The camber is at about neutral. I could probably force a touch more into it, but the car drives and handles better than it ever has right now. It holds a perfectly straight line on the road. No wander or diving at all.
           
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          • Dragonsteel

            Dragonsteel Well-Known Member

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            I only mentioned that because mine leaked and ruined the new paint on my inner fender.
             
          • furyus2

            furyus2 Well-Known Member

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            I keep looking at your setup, and it looks like you have the upper control arms on the wrong side. You should have tons of adjustment with those UCA's. And, I thought the top of the spindle should be behind the spindle center.
             
          • dano

            dano Evil Handy Man

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            He swapped them and they are not. I was thinking they might be B-body?
             
          • 1969VADart

            1969VADart FABO Gold Member FABO Gold Member

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            Completely understand. I had a different MC. Spilled the fluid out all over the MC trying to bench bleed it and the paint peeled off while I was sitting there. I covered just about everything in the engine bay with a blanket while I was working on this to keep the fluid off my parts. It was a tense period.
             
          • 1969VADart

            1969VADart FABO Gold Member FABO Gold Member

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            Yeah, I ran through that question in another thread. This is what they looked like swapped out to opposite sides from the way they are mounted. Clearly not correct.

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          • 1969VADart

            1969VADart FABO Gold Member FABO Gold Member

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            Interesting point that I had not considered. But the part number reflected on my order and in the packing slip is correct for my car. Not to say they couldn't have messed it up, but they look exactly like what PST advertises on their site for the A-bodies.
             
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            • 1969VADart

              1969VADart FABO Gold Member FABO Gold Member

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              Also, looking at Dfr360cuda's set up with the stock UCAs, you can see the top of the spindle is rotated pretty far forward of the centerline as well. That leads me to believe that even with these "fancy" tubular UCAs, the basics of the set up/geometry are going to look the same before adjusting. All that is to say, I don't have the specs on what the set up is right now with my home alignment work, but the car has never driven or handled better after playing with the adjustments some. That is not to say that something might not be off, but driveability has to count for something.
               
            • dano

              dano Evil Handy Man

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              I would ask the supplier how to tell the difference and compare yours. I work in Manufacturing Engineering and yeah, "things" can, do, and will happen.
               
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