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Discuss w-body rear brakes in the alt.autos.gm forum at Car Dealer Forums; I have read that the early W-body gm cars (1988 - 1994) had problems with ...
  1. #1
    Mike
    Guest

    Default w-body rear brakes

    I have read that the early W-body gm cars
    (1988 - 1994) had problems with rear disc
    brakes. I read that the only way for the rear
    disc brakes to be properly adjusted, was to
    constantly use the parking brake.

    I own a 1996 grand prix, and I wonder what
    adjusts the ratcheting device on the rear calipers ?
    Is it still the parking brake ?
    I live in the Midwest, so using the parking brake
    is not a good idea, because the road salt quickly
    rusts the parking brake cables. Once you press
    down on the parking brake, it will most likely
    stay applied, no matter what you do.So most
    people never use the damn thing.

    I am hoping that the 1996 uses a different way
    to keep the rear calipers adjusted. I cant find
    anything in my manual about it (or the internet).

    Please help me to understand how it works.

    Thanks: Mike



  2. #2
    Shep
    Guest

    Default Re: w-body rear brakes

    Dumb question here, are you sure you have rear discs?
    "Mike" <Mike@rocket.org> wrote in message
    news:lDkyg.12228$PN4.9882@tornado.rdc-kc.rr.com...
    >I have read that the early W-body gm cars
    > (1988 - 1994) had problems with rear disc
    > brakes. I read that the only way for the rear
    > disc brakes to be properly adjusted, was to
    > constantly use the parking brake.
    >
    > I own a 1996 grand prix, and I wonder what
    > adjusts the ratcheting device on the rear calipers ?
    > Is it still the parking brake ?
    > I live in the Midwest, so using the parking brake
    > is not a good idea, because the road salt quickly
    > rusts the parking brake cables. Once you press
    > down on the parking brake, it will most likely
    > stay applied, no matter what you do.So most
    > people never use the damn thing.
    >
    > I am hoping that the 1996 uses a different way
    > to keep the rear calipers adjusted. I cant find
    > anything in my manual about it (or the internet).
    >
    > Please help me to understand how it works.
    >
    > Thanks: Mike
    >
    >




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  3. #3
    William H. Bowen
    Guest

    Default Re: w-body rear brakes

    Shep,

    Yep, '96 GP has disks in the rear.

    Regards,
    Bill Bowen


    "Shep" <djsljsrn@capital.net> wrote:

    >Dumb question here, are you sure you have rear discs?
    >"Mike" <Mike@rocket.org> wrote in message
    >news:lDkyg.12228$PN4.9882@tornado.rdc-kc.rr.com...
    >>I have read that the early W-body gm cars
    >> (1988 - 1994) had problems with rear disc
    >> brakes. I read that the only way for the rear
    >> disc brakes to be properly adjusted, was to
    >> constantly use the parking brake.
    >>
    >> I own a 1996 grand prix, and I wonder what
    >> adjusts the ratcheting device on the rear calipers ?
    >> Is it still the parking brake ?
    >> I live in the Midwest, so using the parking brake
    >> is not a good idea, because the road salt quickly
    >> rusts the parking brake cables. Once you press
    >> down on the parking brake, it will most likely
    >> stay applied, no matter what you do.So most
    >> people never use the damn thing.
    >>
    >> I am hoping that the 1996 uses a different way
    >> to keep the rear calipers adjusted. I cant find
    >> anything in my manual about it (or the internet).
    >>
    >> Please help me to understand how it works.
    >>
    >> Thanks: Mike
    >>
    >>

    >
    >
    >
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  4. #4
    William H. Bowen
    Guest

    Default Re: w-body rear brakes

    Mike,

    Your regular service brakes self-adjust themselves as the pads wear
    by piston movement in the caliper bores, just like the front calipers.
    The ratcheting device is used only by the parking brake.

    Where the problem comes in with the parking brake is that if the
    parking brake is not used for a long period of time and the pads have
    worn, the piston will have traveled too far outward for the parking
    brake assembly to properly apply the parking brakes until it is
    applied and released a number of times (the ratchet mechanism has to
    "catch up" with the piston).

    If you never use your parking brake your regular brakes will work
    fine, but your parking brake may get to the point where it will not
    hold the car..

    Regards,
    Bill Bowen
    Sacramento, CA

    "Mike" <Mike@rocket.org> wrote:

    >I have read that the early W-body gm cars
    >(1988 - 1994) had problems with rear disc
    >brakes. I read that the only way for the rear
    >disc brakes to be properly adjusted, was to
    >constantly use the parking brake.
    >
    >I own a 1996 grand prix, and I wonder what
    >adjusts the ratcheting device on the rear calipers ?
    >Is it still the parking brake ?
    >I live in the Midwest, so using the parking brake
    >is not a good idea, because the road salt quickly
    >rusts the parking brake cables. Once you press
    >down on the parking brake, it will most likely
    >stay applied, no matter what you do.So most
    >people never use the damn thing.
    >
    >I am hoping that the 1996 uses a different way
    >to keep the rear calipers adjusted. I cant find
    >anything in my manual about it (or the internet).
    >
    >Please help me to understand how it works.
    >
    >Thanks: Mike
    >


  5. #5
    shiden_kai
    Guest

    Default Re: w-body rear brakes

    William H. Bowen wrote:

    > Where the problem comes in with the parking brake is that if the
    > parking brake is not used for a long period of time and the pads have
    > worn, the piston will have traveled too far outward for the parking
    > brake assembly to properly apply the parking brakes until it is
    > applied and released a number of times (the ratchet mechanism has to
    > "catch up" with the piston).


    Actually, no...this isn't what is happening. The ratchet mechanism
    (if working properly) does not have to "catch up" with the piston,
    it happens automatically. I've replaced numerous pistons on these
    rear calipers, have seen how they operate, and the big problem is
    that they simply stopped working. In fact, what usually ends up
    happening is that not only does the park brake not work properly,
    but the piston is unable to "stay out" against the rotor as the pads
    wear, and you begin to have a low brake pedal. In these cases,
    I've successfully "adjusted" the caliper so that everything works,
    but it doesn't last. The caliper then has to be manually adjusted
    every so often. But since the rear calipers on those cars were
    about 3-400 dollars each (GM), most people were happy to
    simply adjust them.

    The second generation of W-body rear brake calipers had none
    of these problems. I believe they started in 1996.

    Ian



  6. #6
    William H. Bowen
    Guest

    Default Re: w-body rear brakes

    "shiden_kai" <V-L-M@hotmail.com> wrote:

    >William H. Bowen wrote:
    >
    >> Where the problem comes in with the parking brake is that if the
    >> parking brake is not used for a long period of time and the pads have
    >> worn, the piston will have traveled too far outward for the parking
    >> brake assembly to properly apply the parking brakes until it is
    >> applied and released a number of times (the ratchet mechanism has to
    >> "catch up" with the piston).

    >
    >Actually, no...this isn't what is happening. The ratchet mechanism
    >(if working properly) does not have to "catch up" with the piston,
    >it happens automatically. I've replaced numerous pistons on these
    >rear calipers, have seen how they operate, and the big problem is
    >that they simply stopped working. In fact, what usually ends up
    >happening is that not only does the park brake not work properly,
    >but the piston is unable to "stay out" against the rotor as the pads
    >wear, and you begin to have a low brake pedal. In these cases,
    >I've successfully "adjusted" the caliper so that everything works,
    >but it doesn't last. The caliper then has to be manually adjusted
    >every so often. But since the rear calipers on those cars were
    >about 3-400 dollars each (GM), most people were happy to
    >simply adjust them.
    >
    >The second generation of W-body rear brake calipers had none
    >of these problems. I believe they started in 1996.
    >
    >Ian
    >


    Ian,

    All I can say is that is how the action of the older claipers was
    described to be. So far (knock on wood) I've have zero problems with
    the rear calipers on my '94 Regal, but I do know of folks that have
    had problems (and all of them have lived in snow areas where various
    chemicals are used on the roads for snow control).

    BTW, can the newer type calipers be retrofitted onto the older model
    "W" body cars without having to change the rear knuckle?

    Regards,
    Bill Bowen
    Sacramento, CA

  7. #7
    shiden_kai
    Guest

    Default Re: w-body rear brakes

    William H. Bowen wrote:

    > All I can say is that is how the action of the older claipers was
    > described to be. So far (knock on wood) I've have zero problems with
    > the rear calipers on my '94 Regal, but I do know of folks that have
    > had problems (and all of them have lived in snow areas where various
    > chemicals are used on the roads for snow control).


    We had a lot of problems with those older style calipers up here
    in Canada. Actually, that's an understatement. I'd be surprised if
    there was one car from those years that didn't eventually experience
    problems with the rear calipers. Along with what was essentially
    a one way clutch inside the piston that refused to adjust properly, we
    had a lot more issues with the caliper slide pins seizing up. The inability
    of the piston to adjust properly was largely ignored as folks were not
    going to be replacing calipers on that scale.

    > BTW, can the newer type calipers be retrofitted onto the older model
    > "W" body cars without having to change the rear knuckle?


    No, totally different design. Wonderful calipers tho, even with
    tons of miles on the cars, you can screw the piston back into
    the bore with a pair of needle nose pliers. The older style, even
    when relatively new, were a real pain to retract.

    Ian



  8. #8
    Guest

    Default Re: w-body rear brakes


    "William H. Bowen" <wh_bowen@sbcglobal.net> wrote in message
    > All I can say is that is how the action of the older claipers was
    > described to be. So far (knock on wood) I've have zero problems with
    > the rear calipers on my '94 Regal, but I do know of folks that have
    > had problems (and all of them have lived in snow areas where various
    > chemicals are used on the roads for snow control).
    >
    > BTW, can the newer type calipers be retrofitted onto the older model
    > "W" body cars without having to change the rear knuckle?
    >
    > Regards,
    > Bill Bowen
    > Sacramento, CA


    In all respect, the older rear calipers didnt work that way either, Bill.

    The parking brake on most four wheel GM disc brake systems was manually
    applied via a cable to the rear caliper piston assembly

    ( There WERE variations where there was a separate parking brake minidrum
    to hold the vehicle. Corvettes among others might have had such systems.)

    Since there was a solid connection involved through piston to the pad,
    automatic adjustment was a necessity. The piston did not travel freely
    as it would in a front caliper.

    The ratcheting mechanism provided, on those occasions when it worked,
    the adjustment to take the slack out.

    If you didn't use the parking brake, the automatic adjustment didn't work.
    Even if you DID use it, they often froze up and had to be manually freed up.

    When the rear brakes dont apply properly, all the braking energy goes to
    the front rotors and you are soon out of pads and have burned up rotors.

    I have worked on a ton of these, starting in about 1989.




  9. #9
    shiden_kai
    Guest

    Default Re: w-body rear brakes

    HLS@nospam.nix wrote:

    > The ratcheting mechanism provided, on those occasions when it worked,
    > the adjustment to take the slack out.
    >
    > If you didn't use the parking brake, the automatic adjustment didn't
    > work. Even if you DID use it, they often froze up and had to be
    > manually freed up.


    Just some clarification here. Your first sentence above says the
    ratcheting mechanism provides the adjustment, the second
    paragraph says the parking brake is what was necessary to
    make the automatic adjustment work. Am I reading this
    right? The two statements seem to contradict each other.

    Ian



  10. #10
    Guest

    Default Re: w-body rear brakes


    "shiden_kai" <V-L-M@hotmail.com> wrote in message
    news:dRbzg.275785$iF6.270551@pd7tw2no...

    > Just some clarification here. Your first sentence above says the
    > ratcheting mechanism provides the adjustment, the second
    > paragraph says the parking brake is what was necessary to
    > make the automatic adjustment work. Am I reading this
    > right? The two statements seem to contradict each other.
    >
    > Ian


    I get your point, Ian. Those old systems were conditionally** automatic;>)

    Dusting off my brain, here is the way I remember it...
    The ratcheting system on the rear calipers was actuated by the parking brake
    cable.
    When you set the parking brake, it put some clicks on the adjusters inside
    the
    caliper assembly in order to remove the slack. Of course, if they were
    already tight,
    no adjustment was possible or even needed.

    If you didnt activate the parking brake, the rears did not adjust properly
    on these
    models, IIRC. You could quickly get outside the range at which the rear
    brakes
    would apply.

    It was functionally and conditionally automatic -if you used the parking
    brake.
    And if it weren't frozen..

    The newer 4 wheel disc systems dont seem to cause the problems these old
    ones
    did.



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