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Need Help With Electric Trailer Brakes

Discussion in 'Heavy Equipment & Pavement' started by Restrorob, Aug 7, 2007.

  1. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,023

    Hey all,
    We have a tandem axle goose neck for our larger rental equipment. The driver has been complaining about the brakes not working properly.

    It has two 10,000 lb. axles, The first things I checked was the controller and made sure I was getting power to all electro magnetic pads which were fine. Then I pulled the drums to inspect the linings which wear wise looks like they just came out of the box.

    Here is my questions using the picture below;


    When the brake is applied the electro magnetic pad grabs the disc inside the drum and moves the arm to the left to spread the shoes to apply the brakes since there is a stop tab keeping the arm from moving to the right.

    Is this the proper function of these brakes ?
    If not could you explain ?

    Thanks For Any/All Input....
  2. DiyDave

    DiyDave LawnSite Bronze Member
    Posts: 1,695

    for me, but based on your description I think you are right. My understanding of it is that the electromagnet is supposed to grab the disc assuming the wheel is rotating forward. The tab you speak of probably prevents the brake from engaging while the wheel is rolling backwards. I have heard of these magnets being worn out, and also the insulation gone on the wires where they go through the backing plate. Hope this helps!
  3. SiteSolutions

    SiteSolutions LawnSite Bronze Member
    Posts: 1,114

    Check for proper adjustment. I had to adjust mine this Summer and now they work much better; they were virtually not working until I adjusted them.

    From underneath the trailer, with the wheels on and everything assembled, and the trailer supported on sturdy jack stands...

    Find a little rubber plug near the bottom of the back plate of the brake. Pop it out.

    There should be a little toothed doohicky in there. Stick a brake adjustment tool in there if you have one. If not, a slotted type screwdriver works. Use it to turn that adjuster click click click; spin the wheel by hand as you do this. Keep on adjusting until you can't turn the wheel by hand. Then back off a couple clicks.

    I did a google search for "adjust trailer brakes" and found this little nugget of info; I have posted my abridged and condensed version of it here. :)
  4. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,023

    Sorry.....Here's the pic;


    Thanks S/S, We have kept up with the shoe adjustments and the E/M pads/disc and drums all look good.

    This trailer never really stopped well from day one, We have had it around 10 yrs. and I don't recall ever putting shoes on.

    If these brakes function as I posted above and the E/M pad moves the arm to the left to spread the shoes with the tire rotating clockwise that would mean the above brake assembly would need to be on the right side correct ?

    If so why would the short shoe be on the rear instead of the front like on a car/truck ?

    Here is what I'm getting at;
    The brake assembly above (pic) is on the left (driver's side of the trailer). Therefore when the E/M pad is activated it grabs the disc inside the drum but can't spread the shoes because the arm is against the stop tab.

    So my theory is the guy that put the axles under this trailer had a couple six's too many the night before and put them in back-wards. If this is so all we've had is what little braking the E/M pads were doing. This could explain 4
    brake jobs on two trucks.

    When the manual lever on the controller is slid all the way over to engage shouldn't it Lock the wheels up tight ?

    When doing this I can pull off without hardly any drag.....


    JDSKIDSTEER LawnSite Bronze Member
    Posts: 1,163

    We changed our controler out to a digital controler like comes in the newer F_350's and it made a big difference. One of mechanics changed out in his truck and he said the same thing. Instead of grabing hard they grab gradualy, yet better.
  6. Fatboy

    Fatboy LawnSite Member
    Posts: 56

    Picture looks like a left, short shoe to the front, arm swings toward the axle tube. The reverse stop is wrong. My brakes are self adjusting and work in both directions.


  7. Fatboy

    Fatboy LawnSite Member
    Posts: 56

    Just checked the above and it's correct. The short shoe is the primary or front and the long shoe is the rear or secondary. I bet if you get rid of the reverse stop that the wheels will lock. What is the reason for the reverse lock anyway?

  8. SiteSolutions

    SiteSolutions LawnSite Bronze Member
    Posts: 1,114

    Maybe the magnet is pushing instead of pulling? The "too many beers" theory could be right; what if the wires are backward?
  9. Fatboy

    Fatboy LawnSite Member
    Posts: 56

    The magnet should work in either direction and they have no polarity requirements. They can be hooked up either way.

  10. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,023

    OK, Further inspection shows the E/M pad arms are stuck. This is why I couldn't move them the proper direction, Also the E/M pads are worn un-even.

    We are going to clean all brake assemblies up and apply a little white grease to all moving parts and install new E/M pads, Hopefully this will solve the problem.

    Thanks everyone for your replies !

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