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Brake help please

Discussion in 'The Hokey Ass Message Board' started by Nick O, Sep 12, 2013.

  1. Nick O
    Joined: Feb 16, 2010
    Posts: 120

    Nick O
    Member
    from Ohio

    Disc/drum configuration, master cylinder on the firewall above calipers, 7 inch booster, has vacuum, check valve okay, proportioning valve and 10 lbs residual going to the rear. Bleed several times, shoes adjusted up to where the drums barely slideon over the shoes nice drag, front will lock up just fine but rears will not slide in gravel driveway test. Proportioning valve cranked all the way in which should give max rear brake. Wheel cylinders look very good, shoes and drums excellent. any ideas would be greatly appreciated
     
  2. SMOG_GUY
    Joined: Jun 28, 2011
    Posts: 388

    SMOG_GUY
    Member
    from Dinuba

    How is overall braking? Rear brakes do only small percentage of work.
     
  3. V8 Bob
    Joined: Feb 6, 2007
    Posts: 2,774

    V8 Bob
    ALLIANCE MEMBER


    Too large of a rear tire OD for the wheel cylinder size may be the culprit. More info on the brake system would be helpful. :)
     
  4. Nick O
    Joined: Feb 16, 2010
    Posts: 120

    Nick O
    Member
    from Ohio

    It could be better, thats why I'm looking into it I have never felt the were right.

    Maybe the rears should not lock up. I just seems as though the front disc are doing most of the work.
     

  5. Nick O
    Joined: Feb 16, 2010
    Posts: 120

    Nick O
    Member
    from Ohio

    9 inch ford, I will have to measure wheel cylinder bore and shoe size and get back to you. I am not sure.. Wilwood disc up front, Summitt 760100 GM style master and a Summitt 7 inch booster. Crate motor with plenty of vacumm
     
  6. Nick O
    Joined: Feb 16, 2010
    Posts: 120

    Nick O
    Member
    from Ohio

    29.2 rear p255/70r15
     
  7. KRB52
    Joined: Jul 9, 2011
    Posts: 1,055

    KRB52
    Member
    from Conneticut

    No expert by any means, but usually the front do perform most of the stopping. If it is safe to do so, maybe a brief try on pavement and see how they are.
     
  8. SMOG_GUY
    Joined: Jun 28, 2011
    Posts: 388

    SMOG_GUY
    Member
    from Dinuba

    Does the hydraulic system have the factory combo-switch that turns on brake warning light, etc that has the sliding rod in it? It's sometimes called a prop. valve but it does more than that.
    Sometimes the rod slides over and blocks rear hydraulics.
    There are tools that center the valve while you bleed, or you can slowly bleed the front brakes last to help center the rod.
    In the old days we watched the brake idiot light while we bled and when it went out the valve was centered.
     
  9. Nick O
    Joined: Feb 16, 2010
    Posts: 120

    Nick O
    Member
    from Ohio

    no not on this system. Pedal with proper geometry, booster, master and disc front drum rear with a 10 lbs residual valve going to the rears
     
  10. V8 Bob
    Joined: Feb 6, 2007
    Posts: 2,774

    V8 Bob
    ALLIANCE MEMBER


    I had a similar situation with my '32, running 750-16s. I changed the 13/16" cylinders to 15/16" on the 10" Bendix rear drums with much improved balance.
     
  11. Proportioning valve will not help a system that is wildly out of balance. Sort it with wheel cylinder sizes first, then use a proportioning valve to dial it in to perfection.

    Larger rear cylinder will give greater braking to rear.

    This IS how the factory did it, so the cylinders are out there.

    Cosmo
     
  12. F&J
    Joined: Apr 5, 2007
    Posts: 13,221

    F&J
    Member

    Simple test: Drive a few miles, normal stop and go. Come back and feel the rear drums or plates for heat. No heat means they are not working at all, and could be a bleeding issue or?
     
  13. Nick O
    Joined: Feb 16, 2010
    Posts: 120

    Nick O
    Member
    from Ohio

    Put brand new shoes on the rear and turned the drums just to make sure they were true. put 1 inch wheel cylinders on instead of 7/8 that were on. Braking slightly improved, but slightly at best. Still can not lock up rear brakes in a gravel drive. Have bled and re-bled several times. Pedal ratio is 5-1 with a very low pedal. 7 inch booster. Going to turn the front rotors just to make sure they are true and put new pads upfont, thinking of going with something organic instead of heavy metallic. The car is a full fendered 36 Ford and is no light weight by any means
     

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