1. 4mulas

    4mulas Fixem'up

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    I was looking and there is lots of listings for 10 x 2.5” fronts for like 74, and 76 darts etc....

    Be worth a try to go to a shop, have them get a set in and compare them. Maybe you’d get lucky and they’d be the same....
     
  2. Jimacuda

    Jimacuda Well-Known Member

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    There were front brake backing plate changes from 72 to 73.
    Do not know if it changed the shoes tho.

    edit...
    might have both back on the shelf to compare...way back on the shelf...
     
    Last edited: Jan 10, 2020
  3. Jimacuda

    Jimacuda Well-Known Member

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    73 up left, 72 back right 100_4889.jpeg

    shoes look very similar except 73 up shown is 10x2-1/2 and 72 back is 10x 2-1/4.
    Not sure what all has to change for a wider shoe, other than the obvious, drum, shoes...
    Wouldnt the plate have to change as well to keep the geometry of the cyl. correct?
    Or is there a different wheel cyl....hmmm...
    100_4890.jpeg 100_4891.jpeg
     
  4. 4mulas

    4mulas Fixem'up

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    That’s a good post. Man, we’re only talking 1/4” here (1/8” more each side from centreline of the show) I wonder if it really matters?
     
  5. Jimacuda

    Jimacuda Well-Known Member

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    I'd think it could make a difference.
    The actuator rod will be at a slight angle coming off the hyd. cyl. piston.
    Changes the force angles a bit, might make the piston try to cock in the bore.
    Then again there may be enough "play" in the system to take up the 1/8"...
     
  6. 72bluNblu

    72bluNblu FABO Gold Member FABO Gold Member

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    If you measure the offset on the backing plate you'd know for sure. Just lay a straight edge across the back of the plate and measure down to the center hole.

    Clearly the bolt pattern on the spindle is different, but the pressed indent for the spindle actually looks the same between those two backing plates. At least in the picture anyway.

    I did a little looking, the wheel cylinder part number changed going from the '71 parts catalog for the 10x2.25" front drum set up to the '73 parts catalog for the 10x2.5" front drum set up. The part number for the 10" rear drums stayed the same between those years.
     
  7. Jimacuda

    Jimacuda Well-Known Member

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    Sure, make me go measure them...sheesh...:lol:
     
  8. Jimacuda

    Jimacuda Well-Known Member

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    2-1/4" is approx. 1.45"
    2-1/2" is approx. 1.57"

    So it looks like backing plate offset dictates shoe width.
    I suppose you cant really go outboard much with the increase in shoe width without effectively hitting the back side of the wheel...DOH! :lol:

    A few other differences as well...


    100_4899.jpeg 100_4900.jpeg 100_4901.jpeg
     
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    • 72bluNblu

      72bluNblu FABO Gold Member FABO Gold Member

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      Great info! Thanks for doing that, should clear a few things up for folks with the 10” drums up front.
       
    • 4mulas

      4mulas Fixem'up

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      an 1/8” difference in offset, but now it would be good to compare the two listings of wheel cylinders against each other. Maybe they accommodate the different offset’s so if you changed everything in pairs you’d be okay?.....
       
    • Jimacuda

      Jimacuda Well-Known Member

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      glad I didnt save it all for no reason:rofl:

      well, I did stack them neatly on a shelf out back a couple decades ago as they were stripped...
      then promptly lost them as things collected in front of them...:D



      100_4136.jpeg
       
    • Jimacuda

      Jimacuda Well-Known Member

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      look at the backside pics...the wheel cyls. physically wont interchange.

      As I see it you have to match the drum to the shoe width to the backing plate offset.
       
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      • 4mulas

        4mulas Fixem'up

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        Totally. Didn’t look but that’s 1 year old peg board 101 stuff. Square don’t fit in round and vice versa. Lol
         
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        • trapster

          trapster Well-Known Member

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          I hope I am not high-jacking this thread, but I pulled a drum off of the back of my 64 dart, 8 3/4 10" x ?, because it locks up when I step on the brakes, and noticed that there is a good 1/4 inch of more of unused drum on one side of the shoe. The shoe measures less than 2", so I am assuming someone, not me, put the wrong shoes on it. The question is do I need 2 1/4 or 2 1/2 shoes ? or do I need to measure the drum better? I know I need a different proportioning valve, that is a different subject.


          Thanks


          PS. dual master, front disks from a 69 and all small pattern.
           
        • Mattax

          Mattax Just the facts, ma'am FABO Gold Member

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          Above discussions cover front drums.
          If the 8.75 came complete from a '69 A-body, the rear drums are nominally 10 x 1.75". Shoe frames should be stamped 331 and the adjuster hardware should be the '69 up type.
           
        • mobileparts

          mobileparts Well-Known Member

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          Hey trapster,
          Replied to you presently. Check your P.M.
          Yours, Craig.....
           
        • Ron816

          Ron816 Well-Known Member

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          Found!, year one had them.
           
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