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Thread: amphi : What's up with my brakes????

  1. #1

    Default amphi : What's up with my brakes????

    What's up with my brakes????
    Post by amphi on May 18, 2006, 10:42am

    They make this loud deep screeching sound --- like a semi – during moderate to heavy breaking. My truck is very heavy --- nearly 9,000 lbs with the fire equipment and a full load of water (260 gal). It has a vacuum assist break booster and will stop on a dime. You've heard of coming to a screeching halt --- well this does that --- not tires but brake noise. Really loud very deep squeal. Any ideas?

    I have pulled all four drums and nothing seems wrong other than worn lining. Not worn completely out but getting pretty close. The thinnest has about 50 to 60 thousands before contacting the rivets. No oil or fluid leaking on the brakes. Drums look good – maybe a little out of round but all four are smooth and shiny.

    I marked each drum and put it back in its original location. I can see by the maintenance records the FD has had these off --- I doubt if they put them back as original. What is the reason for this? Why can't they be rotated or moved about?

    The shoes on all four wheels are installed with the small (short) shoe to the front. Is this correct?

    Does anyone recognize the brake booster pictured? Record show hydro-vac #379776

    Here are some pictures.


    Right front



    Left rear



    All look like this



    Brake booster


    Thanks for any replies
    Gary

  2. #2

    Default socal715 :

    Re: What's up with my brakes????
    Post by socal715 on May 18, 2006, 10:44am

    Looks fine to me... but im not a huge drum brake guy... your rig weighs 9000#'s? and it actually stops with stock brakes? (only kidding)

  3. #3

    Default amphi :

    Re: What's up with my brakes????
    Post by amphi on May 18, 2006, 11:18am

    Yep!!

    Weighed in at 6,745 lbs with me and a half tank of fuel added 260 gals of water at 8.345 lbs per gal. Total 6,745 + 2,169.7 = 8,914.7 lbs




    Taken yesterday 05-17-2006 Fully loaded.

    See the little sag between the bed and cab.

  4. #4

    Default socal715 :

    Re: What's up with my brakes????
    Post by socal715 on May 18, 2006, 11:27am

    Wow... it barely sagged. I don't think my truck will even move when i load it up tonight to go camping.. probably only weigh in @ 500-600lbs

  5. #5
    Join Date
    Sep 1998
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    Default brute4c :

    Re: What's up with my brakes????
    Post by brute4c on May 18, 2006, 11:54am

    The drums are "indexed" with the hubs for purposes of balance and straightness...

    A while back Barrman took his off in order to facilitate turning his drums. He found that each one was off a little in relation to the others and would make turning a drum with one hub have a different true center than it would have if it were installed to a different hub...in other words, each drumand hub needed to stay with each other and stay indexed as they were on the hub...he can explain it better when he has time I am sure...


    As far as your booster, never played with one like that so I cant say too much there...I know that a conventional, between the master and firewall, type will give a pedal that is as hard as a rock when they go bad...that may be no help at all to you though.


    Ever put a light coat of grease on the back edge of the shoes where they rub on the drum when they are moving? This helps get rid of squeaks and such...the shoe can basically vibrate on the backing plate as the forces are working on it...pushing in with the fluid, trying to be ripped out by the rotation...

  6. #6

    Default amphi :

    Re: What's up with my brakes????
    Post by amphi on May 18, 2006, 12:04pm


    Quote:
    Ever put a light coat of grease on the back edge of the shoes where they rub on the drum when they are moving? This helps get rid of squeaks and such...the shoe can basically vibrate on the backing plate as the forces are working on it...pushing in with the fluid, trying to be ripped out by the rotation...


    Are you talking about where they contact the back-plate? If so I didn't do it but will.

    My noise is definitely shoe to drum squeal or growl. I do get some surging.

  7. #7
    Join Date
    Sep 1998
    Location
    North Central Wisconsin
    Posts
    11,520

    Default brute4c :

    Re: What's up with my brakes????
    Post by brute4c on May 18, 2006, 12:19pm

    Yep...a little grease on the backing plat n the area that the shoes hit when they move...obviously not a lot, but some lube to keep them moving freely...

    Might have a combo thing going on here....remember this is a guess...

    If the shoes are worn to the thin end AND he brak springs arent completely up to snuff, possible that the ccombination of these is letting the shoes "bounce" off the drum as it goes around...not really bouncing as in leaving the surface and coming back to it but losing some of the pressure that should be exerted steadily due to the springs being old and being extended more due to the shoe wear....

    Make any sense?

    This is a guess, this is only a guess...do not pass go, do not collect $200...

  8. #8

    Default amphi :

    Re: What's up with my brakes????
    Post by amphi on May 18, 2006, 12:28pm

    Sounds reasonable!! Gotta go --- I'll be back to check this thread later.
    Thanks
    Gary

  9. #9

    Default kaiser715 :

    Re: What's up with my brakes????
    Post by kaiser715 on May 18, 2006, 12:40pm

    Ummm, so what if you've mixed the drums up...any way to get them matched up again?

    How do they line'em up in the first place????

  10. #10

    Default drvnkaiserdaily :

    Re: What's up with my brakes????
    Post by drvnkaiserdaily on May 18, 2006, 12:52pm

    I have found as the lining on the pad gets thin,it will allow the metal part of the shoe to contact the lip at the back of the braking surface of the drum(inside edge of drum sometimes gets a lip just past where the pad wears) that ridge sticking up from the drum can contact the shoe just past the outer edge of the lining and cause the metallic sound you have described

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