Differences in A Body brake systems

Brakes for your Classic Mopar

  1. Rat Patrol

    Rat Patrol Well-Known Member

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    Interested in knowing the difference between the front disk set up on a US 72 A Body, and a 74 US A body?

    Are the rotors a different diameter or thickness?

    Is the Bolt pattern different?

    Differences in caliper etc?
     
  2. jarvitron

    jarvitron Well-Known Member

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    Pretty sure that 72 was still small bolt pattern (5x4") and the 74 would be big bolt pattern (5x4.5"), and the only "interchange" would be spindles/rotors/calipers as a whole swap versus interchanging any individual parts. Could be wrong on the calipers, they might work, others would know better.
     
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    • larry b

      larry b Well-Known Member

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      my 72 duster was a factory small bolt pattern kelsy hayes 4 piston caliper front brake system sorry about the spelling.
       
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      • Rat Patrol

        Rat Patrol Well-Known Member

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        Thanks Larry / Jarvitron - I appreciate the info.

        Oz Mopars were 4.5 bolt pattern in 1972, which is part of the reason for me asking - trying to work out what was different between ours and yours .

        Maybe others can help out with the question.... 72 vs 74?
         
      • Dartnut

        Dartnut Don't hate me because i'm beautiful

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        Everything is different other than lower control arms and sway bar tabs.
        '73 and newer had bbp and 1/2'' studs.
        '72 and older had sbp, and 7/16'' studs. (Kelsey/Hayes 2 piston calipers)
        Master cylinders were different as well as the brake booster.
        Sway bars were different as well as other steering and suspension parts.
         
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        • cudamark

          cudamark FABO Gold Member FABO Gold Member

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          Yes, as mentioned, everything is different between the '72 and older KH 4 piston caliper brakes and the '73-6 single piston brakes. They don't share any common parts.
           
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          • 2 Darts

            2 Darts A-body Addicted

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            Yes. The 72 uses a slightly greater diameter, thinner rotor.

            Yes. In the US the 65-72 disk brake used a 4-inch bolt pattern. The 73 and later used a 4½-inch bolt pattern. Please note that the 73 and later drum brake cars still used a 4-inch bolt pattern.

            The 72 and earlier US disk brake cars used a fixed caliper unit manufactured by Kelsey-Hayes. This design did not require the caliper be removed for renewal of the pads. However, it is less tolerant of rotor runout. The caliper can be easily identified by an external (and vulnerable) balance tube that supplies brake fluid pressure to the outer pistons on the caliper.
            By contrast, the 73 and later disk brake cars used a floating caliper design. I'm thinking this was a Delco-Moraine product, but not certain. This design is simpler to maintain, less prone to leakage, and more tolerant to rotor runout.

            There were three different proportioning valve schemes used in this era. The first was an external valve near the master cylinder. The second was a proportioning valve incorporated in the Tee on the rear axle. The third, and most likely for the 74, was a combination distribution/metering/proportioning valve located on the firewall. This valve is identified by five hydraulic connections (2 from the master cylinder, 1 from each front wheel, and one to the rear brakes).
             
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            • babalui56

              babalui56 Member

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              Hi, Since you guys seem to really know what you are talking about i have a question. I am doing a resto on a 68 Cuda Convertible. While pulling the front brakes apart I found they were a single pision Caliper. The casting number is KH86188 then a 339 below. The best i can figure is this is from a 1974 and up. So i am not sure what pads and rotor i need. I also want to order FE Parts but am holding off until i am sure i know what the heck I have, Got lots of pic and can send more numbers if needed. Would appreciate the Help. Jerry
               
            • crackedback

              crackedback FABO Gold Member FABO Gold Member

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              start a thread in this section with pics of what you have.
               
            • scrappydoo

              scrappydoo Well-Known Member

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              Does anyone know if the Australian spindles will swap out with the usa spindles?
              I have a 67 Dodge Dart with 10" boosted drums and I want to fit disk brakes.
              I'm hoping the local 1972 and later spindles will bolt straight on.
              Thanks.
               
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