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Thread: Front Disc conversion. Rear Drum brakes locking up

  1. #1

    Default Front Disc conversion. Rear Drum brakes locking up

    Hi,

    Have a front disc brake kit installed on a 57 chev.
    Rear brake cylinders were seized and now replaced. Now rear drum brakes are locking up first.
    Any suggestions?
    How do I adjust the proportioning valve if it is that?

    Dave

  2. #2

    Default

    Good Morning,

    On the proportional valve there is not an adjustment. I would say most likely loosing up the adjuster on the rears would help. sounds like they might be on the tight side.
    Aaron Strietzel
    Email Aaron
    Classic Performance Products Inc.
    378 E. Orangethorpe Ave
    Placentia, CA 92870
    Visit Our Site
    714/522-2000
    714/522-2500 fax

  3. #3

    Default

    Quote Originally Posted by CPPAaron View Post
    Good Morning,

    On the proportional valve there is not an adjustment. I would say most likely loosing up the adjuster on the rears would help. sounds like they might be on the tight side.
    Hi aaron,

    I am assured the drums are adjusted correctly.
    Front disc were working fine with seized rear drum cylinders, now replaced cylinders back drums are locking up when brakes pressed.
    Either wrong cylinders installed or faulty proportioning valve?
    Do the proportioning valves stick/fail often?

    Dave

  4. #4

    Default

    No issues with the valves on these really... I would double check you have the correct wheel cylinders. If the bore is too large this could happen.
    Aaron Strietzel
    Email Aaron
    Classic Performance Products Inc.
    378 E. Orangethorpe Ave
    Placentia, CA 92870
    Visit Our Site
    714/522-2000
    714/522-2500 fax

  5. #5

    Default

    Quote Originally Posted by CPPAaron View Post
    No issues with the valves on these really... I would double check you have the correct wheel cylinders. If the bore is too large this could happen.
    Hi Aaron,

    Have 1" cylinders fitted to the rear.
    Is it possible to have the wrong proportioning valve? Would a disc/disc valve cause this?

    Thanks,
    Dave

  6. #6

    Default

    Only if it had a 4 wheel disc prop valve. There should be a "2" stamped on the bottom of it and a rubber cap in the front.
    Aaron Strietzel
    Email Aaron
    Classic Performance Products Inc.
    378 E. Orangethorpe Ave
    Placentia, CA 92870
    Visit Our Site
    714/522-2000
    714/522-2500 fax

  7. #7

    Default

    Quote Originally Posted by nailz77 View Post
    Hi,

    Have a front disc brake kit installed on a 57 chev.
    Rear brake cylinders were seized and now replaced. Now rear drum brakes are locking up first.
    Any suggestions?
    How do I adjust the proportioning valve if it is that?

    Dave
    I know this is an old thread, but I was wondering if you found a solution to this. I have the same problem with my '55 chevy. Disc front, stock drums in rear. Thanks

  8. #8

    Default Poor advice !!!

    This is exactly the crappy advice CPP will give you after they send U the wrong parts. Of course the proportioning valve could be defective or incorrect !!!!!

  9. #9
    Junior Member
    Join Date
    Jun 2019
    Location
    Salem Oregon
    Posts
    2

    Default rear wheel lock up

    If you have not fixed yor problem yet, you might have to much pressure to the rear brakes. One possible solution is to install a adjustable proportioning
    valve and decrease pressure to rear brakes

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