brake pads won't fit

Brakes for your Classic Mopar

  1. perko

    perko Well-Known Member

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    Hey all,
    This is seriously stressing me out. I'm trying to replace the brakes and the rotors on my 73 plymouth duster. Discs up front and drums in the rear. I've got the cylinder pushed back as far as it will go but I need like 2mm more space to get these pads on. Has anyone else had this problem? can I sand down the pads a little? The new ones look the same as the old ones.
     
  2. 67Dart273

    67Dart273 FABO Gold Member FABO Gold Member

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    Might be junk behind the pistons. You retract them with a C clamp?
     
  3. SGBARRACUDA

    SGBARRACUDA ROY FABO Gold Member

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    Are you using new rotors? If your sure your pistons are all the way in, than you have two choices. Make the pads thinner or turn rotors. I would sand the pads.
     
  4. perko

    perko Well-Known Member

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    Yeah, new rotors. we're talking millimeters here. the piston is all the way in its a few mm below the rubber boot. I used a C clamp.

    How do i sand the pads? can I use a rotary sander or should i use a belt sander?
     
  5. SGBARRACUDA

    SGBARRACUDA ROY FABO Gold Member

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    What ever method that you feel you can reduce the thickness equally across the entire surface. I have used a belt sander in the past.
     
  6. perko

    perko Well-Known Member

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    What grit did you use?

    I've already been to NAPA four times, skips auto twice, and orilles once. I think its about beer 30 out here
     
  7. 72bluNblu

    72bluNblu FABO Gold Member FABO Gold Member

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    Pistons aren't all the way back. Could be crud behind the pistons, as Del suggested. If that's the case it's time for a caliper rebuild. I wouldn't do anything to the pads, if they're the right part the fact that they don't fit suggests something else is wrong.

    I've never had a set of disk brake pads not fit if they were the correct pads for the application, regardless of new rotors etc. So either you've got the wrong pads, or something else is going on unless you can prove otherwise.

    A company making the rotors or the pads too thick isn't usually an issue, usually it's the opposite to save money on production. What brand are the pads and rotors?
     
  8. 67Dart273

    67Dart273 FABO Gold Member FABO Gold Member

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    I can't imagine any hand held sander being accurate enough. If you get them "out of parallel" the pads can cock and bind, etc.

    As much as I'd hate to turn new rotors, that is probably what I'd do. I would also examine one or two more sets of pads and make certain the ones you bought aren't an oddity.
     
  9. nm9stheham

    nm9stheham Well-Known Member

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    If you sand the pads, then get some of the mesh drywall sanding sheets from any harware or building supply store, in a grit like about 180 or 220 and with the black type of grit. Place the grit mesh on a very flat surface and work in a circular motion and reverse the pads every 10-15 seconds. I sand the racing pads lightly on my rally cars to get a fresh surface and never, ever have an issue.

    BUT in your case, 2mm is .080", and that is a LOT more than I take off. So either the pads are wrong or the pistons are not fully back, as said.
     
  10. hemi71x

    hemi71x FABO Gold Member FABO Gold Member

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    Get yourself a sheet of 80 grit sandpaper, put it on a flat surface, (the floor) Get the pad, sand away, until you feel you took off enough material to that pad.
    Repeat, on the others.

    By the way, it isn't that uncomon for pads to be tight, not fit, if replacing both new rotors, and pads at the same time.

    Manufacturers tolerances aren't always the greatest when dealing with modern day parts.

    When i was a full time wrenching mechanic, i ran across this from time to time, doing a full brake job.

    Sanding the pads did the trick.

    Don't loose any sleep doing it.
    Doing brakes isn't rocket science.
     
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    • AJ/FormS

      AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s

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      I use a micrometer to keep track of where I'm at. When I'm in the ballpark, I put the pads face to face, and even 'em up, and make sure the steel backers are parallel.Do not use Garnet paper, the grit lets go and transfers into the pads. I have used carpenters emery paper,and wire brushing the pads when done.
       
    • DoctorDiff

      DoctorDiff Well-Known Member

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      If you bought calipers from Napa, there is a good chance they were rebuilt with the wrong pistons. I ran into this several times.
       
    • cudascott

      cudascott wish I had a Hemi

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      You just had to mention NAPA now Dell is gonna go off on a rant again:D
       
    • Rapid Robert

      Rapid Robert Well-Known Member

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      rebuilt calipers are dirt cheap & reliable. You might go to your parts house & eyeball one of em & compare the piston recess depth to yours. If you do get new ones get ones for a 76 A body (2.75" bore) cuz the more front bias the better (same price too). If you do sand have a method to get em straight, (I'd be leery) & if hand sanding going in a figure eight motion works the best for an even/level cut
       
    • 72bluNblu

      72bluNblu FABO Gold Member FABO Gold Member

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      This is exactly the kind of thing that needs to be investigated here. Sanding the pads is treating the symptom and most likely not the problem. Every time I've encountered a brake pad that wouldn't fit the problem was something else in the system, not the pad.
       
    • mderoy340

      mderoy340 Well-Known Member

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      If the calipers are used, extended the pistons and use the c clamp to compress with the bleed open. If crude comes out while bleeding this is your problem.
       
    • nm9stheham

      nm9stheham Well-Known Member

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      Another possibility..... make sure the pistons are staying 'in' on both sides if you are compressing one side in, then moving the C-clamp to the other side to compress the other piston in. Sometimes, compressing the 2nd piston in will move the 1st piston back out a bit if it is not restrained.
       
    • perko

      perko Well-Known Member

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      no crud came out of the bleeder. I've never done brakes on this care but I have done a bunch on other cars. This piston looks like its in all the way to me, the thing is sitting below the rubber boot, but they are old so theres a good chance they crapped out. I think i'll see if anyone has calipers in stock around here. Otherwise i'll get to sanding. I really think its the new brakes and new rotors being just a wee bit too big.
       
    • TrailBeast

      TrailBeast Slightly Twisted Member

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      If this happened to me I would hit the brake pedal with two real short strokes and push the pistons back in again and see what happens.

      Is the problem the same on both sides, or have you tried that yet?
       
    • d5667

      d5667 Member this?

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      Diff is correct it is called"industry standards". If you are concerned about taking a few thousandths off of a brake pad face then you will really go berserk when you use your brakes.
       
    • teringer

      teringer ase master hall of fame FABO Gold Member

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      I just went through the same thing on my 73 duster ,bought every thing new /rebuilt and I replaced the rotors,calip,rubber hoses, and pads, after comparing all parts I found the new pistons in the calipers were taller then the ones that came out by .050 so after flat sanding the pads until they fit with a little extra for when they got hot ,no problem so far (rock auto) but still saved $ AND FOR 12$ I KEEP THE CORES TO REBUILD
















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      • perko

        perko Well-Known Member

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        Yeah, I got frustrated, put the pads in a vice and hit them with a belt sander. They seem to work. They're a million times better than before so its a win in my book.
         
      • furyus2

        furyus2 Well-Known Member

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        I would recommend not using the 76 up calipers. I did this, and due to the larger bore, I had to change from a 15/16 MC to a 1 1/32 bore MC. The 15/16 did not move enough volume to operate the larger calipers.
         
      • 72bluNblu

        72bluNblu FABO Gold Member FABO Gold Member

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        Not sure what your particular brake issue was, but I use a 15/16" master with the larger 2.75" bore calipers. They work great. Keep in mind that all of the B/E body pin type calipers had a piston bore of 2.75". I just converted my Challenger over to manual brakes with a Dr. Diff 15/16" master cylinder and had no issues with the pedal.
         
      • inertia

        inertia Well-Known Member

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        I use the 15/16ths bore M/C regularly with any size caliper and get fantastic results.

        Not sure what your problem was, but it wasn't the M/C.

        cheers
         
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