1. 4mulas

    4mulas Fixem'up

    Messages:
    469
    Likes Received:
    124
    Joined:
    Dec 23, 2006
    Location:
    Alta
    Local Time:
    1:31 AM
    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

    Messages:
    1,676
    Likes Received:
    532
    Joined:
    Nov 10, 2006
    Location:
    Phoenix AZ
    Local Time:
    2:31 AM
    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

    Messages:
    1,676
    Likes Received:
    532
    Joined:
    Nov 10, 2006
    Location:
    Phoenix AZ
    Local Time:
    2:31 AM
    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

    Messages:
    469
    Likes Received:
    124
    Joined:
    Dec 23, 2006
    Location:
    Alta
    Local Time:
    1:31 AM
    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

    Messages:
    1,676
    Likes Received:
    532
    Joined:
    Nov 10, 2006
    Location:
    Phoenix AZ
    Local Time:
    2:31 AM
    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

    Messages:
    10,037
    Likes Received:
    4408
    Joined:
    Nov 28, 2008
    Location:
    NorCal
    Local Time:
    1:31 AM
    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

    Messages:
    1,676
    Likes Received:
    532
    Joined:
    Nov 10, 2006
    Location:
    Phoenix AZ
    Local Time:
    2:31 AM

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

    Jimacuda Well-Known Member

    Messages:
    1,676
    Likes Received:
    532
    Joined:
    Nov 10, 2006
    Location:
    Phoenix AZ
    Local Time:
    2:31 AM
    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
     
    • Like Like x 1
    • 72bluNblu

      72bluNblu FABO Gold Member FABO Gold Member

      Messages:
      10,037
      Likes Received:
      4408
      Joined:
      Nov 28, 2008
      Location:
      NorCal
      Local Time:
      1:31 AM
      Great info! Thanks for doing that, should clear a few things up for folks with the 10” drums up front.
       
    • 4mulas

      4mulas Fixem'up

      Messages:
      469
      Likes Received:
      124
      Joined:
      Dec 23, 2006
      Location:
      Alta
      Local Time:
      1:31 AM
      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

      Messages:
      1,676
      Likes Received:
      532
      Joined:
      Nov 10, 2006
      Location:
      Phoenix AZ
      Local Time:
      2:31 AM
      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

      Messages:
      1,676
      Likes Received:
      532
      Joined:
      Nov 10, 2006
      Location:
      Phoenix AZ
      Local Time:
      2:31 AM
      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.
       
      • Agree Agree x 2
      • 4mulas

        4mulas Fixem'up

        Messages:
        469
        Likes Received:
        124
        Joined:
        Dec 23, 2006
        Location:
        Alta
        Local Time:
        1:31 AM
        Totally. Didn’t look but that’s 1 year old peg board 101 stuff. Square don’t fit in round and vice versa. Lol
         
        • Like Like x 1
        1. This site uses cookies to help personalize content, tailor your experience and to keep you logged in if you register.
          By continuing to use this site, you are consenting to our use of cookies.