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trailer brake test/repair

Discussion in 'Tow & Trailer' started by bigjbear, Jul 7, 2005.

  1. bigjbear

    bigjbear 1 ton status Staff Member Moderator

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    Help guys! I started to set up my trailer brakes today and wanted to test them. First, I took the red lead and touched it to a bat (+) & the white to a bat (-). I expected the brake to lock up. It did nothing. So I pulled the drum off and it looks like this inside:
    [​IMG] [​IMG]
    [​IMG]

    Basicly the same as anything else, just no wheel cyl and some type of pick-up looking thing at the bottom. So do I need to do something else to test it, or am I going to the trailer place to buy stuff? TIA.
     
  2. dhcomp

    dhcomp 3/4 ton status Premium Member

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    Only thing i see is rust and almost worn out pads.

    Sorry i can't be of more help....maybe the pads are too worn to do anything?

    Did you try to engage it with the drum off to see if it does anything at all?
     
  3. bigjbear

    bigjbear 1 ton status Staff Member Moderator

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    Tried that, too. It doesn't do jack. The shoes are worn but I doubt they need replaced yet. They're the bonded type and look to be around 50%. Either way, that's not going to keep them from engaging. I've done a little research & measuring so I know this much now; the deal at the bottom is an electro magnet and my shoes are 12" x 2". (yes, its a big-ass trailer) Also, I was applying juice to both brakes on this axel while doing this, but not the other axel. Has anybody messed w/ this stuff????
     
  4. 88sub4x4

    88sub4x4 1/2 ton status

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    The big thing with the wires on the bottom is the magnet. When it gets power it magnetises to the drum, and the momentum of the drum spinning tries to pull the magnet along with it, and this magnet moving pushes on the pads and makes them engage. It is hard to test, unless you have the wheel off the ground, and spin it, and have someone actuate the brakes. Then you will notice a difference in the spinning if the brakes are working. The magnets go bad fairly often, mainly the wires rip out of them.
     
  5. woody9

    woody9 1/2 ton status

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    just went thru some of this with my camper, but the problem was totally different!
    I had 3 of the 4 not getting ANY juice! No juice - no brakes!
    Gawd, does it stop mo-betta now! :)

    I think when the juice hits that magnet, it tries to grab the drum.... that's turning! as it tries to grab it, it then acts like a wheel cyl and applies more force.

    I'd do what was recommended above. Get the wheel(s) off the ground, get 'em turning and then apply the juice. Not sure of other ways, but you may want to try the Mfr's web site (mine were dexter). They give some of those scientific numbers to check here & there (volts, amps, draw, etc) and that may help confirm if a magnet is dead.
    hope this helps! (or at least that you're not behind me with a load on!!)

    :)
     
  6. bigjbear

    bigjbear 1 ton status Staff Member Moderator

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    Thanks for the tips guys. Mine are also Dexters.
     

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