Brake Adjustment

Discussion in 'Flat Fender Tech' started by DanStew, Aug 27, 2017.

  1. Aug 27, 2017
    DanStew

    DanStew Incorrigible. Staff Member Sponsor

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    Driving the CJ2a and I am still not crazy about the brakes. I have 11 inch brakes in the front, 9 in the rear and i upgraded the MC to one from a 74 CJ5. That being said. I have bled the brakes numerous and numerous of times and all the air seems to be gone. I have adjusted the front brakes but I am not sure how much drag you should have. I have adjusted them so that it is dragging a bit, you can hear the shoes contacting the drum but it can spin and not immediately stop the drum. My brake pedal goes all the way to the floor but it does stop, but nothing near pressure I am happy with or feel safe with. I am using the correct output in the MC for the front brakes, I do not have any leaks. What else to look at?
     
  2. Aug 27, 2017
    47v6

    47v6 junk wrecker! Sponsor

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    Is one of your rubber brake hoses ballooning out? Master cylinder rebuilt? Air out of brake switch?
     
  3. Aug 27, 2017
    DanStew

    DanStew Incorrigible. Staff Member Sponsor

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    All new parts. no balooning and the MC is new. I didnt notice any leaks on the brake switch, and that switch i have on a T to the rear brakes, so it shouldnt affect the front circuit. I had the cap off the MC and i can push the pedal and see the nice gyser out of the side of the resovior for the front brakes. i jsut dont think it is adjusted enough, but not sure how tight, I dont want to burn up shoes.

    It is a sad thing that I dont know drums, i ahve changed out all my jeeps to disc brakes when i got them, Oye Vei
     
  4. Aug 27, 2017
    73 cj5

    73 cj5 In Rust We Trust Sponsor

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    Iirc there's a feeler gauge cutout in the 9" drums and you check the drag that way. Look up a manual for an mb/gpw and it shows how to adjust the brakes.
     
  5. Aug 27, 2017
    DanStew

    DanStew Incorrigible. Staff Member Sponsor

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    The fronts are 11 inchers.
     
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  6. Aug 27, 2017
    73 cj5

    73 cj5 In Rust We Trust Sponsor

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    Doh!! Does the 74 CJ mc have a residual pressure valve? I know the stock mc for the 2a had one.
     
  7. Aug 27, 2017
    Glenn

    Glenn Kinda grumpy old man Staff Member Sponsor

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    Master cylinder push rod adjustment?
     
  8. Aug 28, 2017
    45es

    45es Sponsor Sponsor

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    Have you adjusted the rear brakes yet? You have confirmed that the brakes are bled and adjusted but the rear brakes must also be bled and adjusted or you will never get the full pedal you desire.
     
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  9. Aug 28, 2017
    DanStew

    DanStew Incorrigible. Staff Member Sponsor

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    That is the wild card there. I had the rears "adjusted" but I pulled out of adjustment to check out why i had a bad wobble in the rear, and I broke off a stupid bleeder on one of the wheel cylinders in the rear. I was under the impression that since it is a differnt circuit and it is the secondary one that activates later so it shouldnt matter much. Is this bad thinking? I was also under the impression that the fronts do most of the work.

    I have the pushrod adjusted, It is not riding the MC, but has a touch of freeplay so there is not pressure on MC at rest.
     
  10. Aug 28, 2017
    45es

    45es Sponsor Sponsor

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    Although the front brakes do most of the work, the rears are needed and must be in good working order for the entire system to function correctly. One of the indicators of a failure in either the front or rear brake circuit is a low pedal. To better understand the mc operation, look at a diagram or a rebuild kit for the '74 mc that you have. You will note that the plunger assembly within the mc bore consists of two plungers separated by a spring. During a failure of either brake circuit (front or rear), the brake fluid that normally surrounds the spring within the bore and maintains the spacing of the two plungers is allowed to return to the reservoir, the spring compresses and the pedal is low.
     
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  11. Aug 28, 2017
    47v6

    47v6 junk wrecker! Sponsor

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    Poor pedal is almost always related to rear brakes.
     
  12. Aug 28, 2017
    DanStew

    DanStew Incorrigible. Staff Member Sponsor

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    OK, I will adjust them back up tonight. Thanks!!!
     
  13. Aug 28, 2017
    45es

    45es Sponsor Sponsor

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    One last thing. Your experience points out the importance of a differential pressure (note: I did not say proportioning valve or combination valve although they do have the warning lamp circuit.) switch with working indicator lamp when using a dual circuit master cylinder in a system similar to yours. Although you knew the rear brakes were not working, the warning lamp would have been a visual reminder in addition to the lower brake pedal to find the problem.
     
  14. Aug 28, 2017
    wheelie

    wheelie beeg dummy Sponsor

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    FWIW, I adjust my drum brakes the same way you have described. That's all i have. :rolleyes:
     
  15. Aug 28, 2017
    Focker

    Focker Rust Never Sleeps Staff Member Sponsor

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    Did you bench bleed the new MC?
     
  16. Aug 28, 2017
    DanStew

    DanStew Incorrigible. Staff Member Sponsor

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    Yes I did.
     
  17. Aug 28, 2017
    PeteL

    PeteL Member Sponsor

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    During the process I like to push the pedal hard once or twice to "center" the shoes equally.

    As to "how much drag" I kind of like it when I can more or less hear them rubbing, but can't feel any resistance.
     
  18. Aug 28, 2017
    Keys5a

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    Pull a drum or two off and look at the fresh wear pattern on the shoes. Did you cam in the shoes to the drum? If the drums have been turned, fresh shoes will contact just the center part of the shoe lining. Brake shops have a machine that cams in, or grinds the high contact point down so that the whole shoe (or nearly all the shoe) conforms to the drum. This way, you get full braking action without driving for 8,000-10,000 miles to wear the shoes in to the drum. If you are getting only a small contact spot on your shoes, your brakes are going to have marginal stopping power at best.
    I have seen ill-fitting shoes on nearly everything drum brake I have pulled apart for the past 20 years. I guess nobody knows how drum brakes are supposed to work now-a-days!
    -Donny
     

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