Trailer brakes

37 chief · Apr 8, 2009

I have a Big Tex trailer I use to haul my tractor, and mower. I replaced the axel's with more heavy duty ones. The brakes have a center donut with lining that is pulled into another flat circle on the drum which apply's the brakes. My question if anyone knows this system is: Does the center donut which is the magnet when the brqakes are applied, rub on the drum flat piece all the time? When I rotate the wheel I hear a scrapiong sound. Thanks for any answers. Stan

Dutchman · Apr 8, 2009

It sounds to me like you are talking about Electric brakes...
If that's the case .. YES the Magnet drags on the big cicle .. The cleaner it is the better the BRAKES Work ... if they are set right .. THERE will be some draging.. not very much or it will ruin the Magnet...

I may be COMPLETEly wrong ... but THATS what it sounds to me ...
Mark

37 chief · Apr 8, 2009

That is what I am talking about. Do you know the procedure to adjust the magnet? Stan

Michael Soldan · Apr 8, 2009

Stan, when the magnet is activated against the surface face of the drum it should pull an activating lever back which expands the shoes at the top of the backing plate causing them to rub against the drum. The magnet does not do the braking, it causes the lever to pull back activating the brake shoes against the drum. There are three ways to tell if electric brakes are working. When applied you can hear a buzz sound coming from the wheel when parked. The surface face of the drum is shiny it indicates the magnet is activating against it and if the drum area is shiny it indicates the shoes are being pulled out against it. Any two of those conditions would indicate the brakes are working. If the magnet is a burnt bluish colour there is a problem. If you touch your test light to the magnet wires(surface wire of the magnet) and it lights there is a problem. Electric brakes aren't that difficult its just that they don't work half the time for the simplest of reasons..poor ground, rusty, adjusters need freeing up and set,bad magnet, moving parts need lube..you need to stay on them to keep themworking

Michael Soldan · Apr 8, 2009

I forgot, the scraping sound is just the shoe adjuster holding the shoe fairly tight to the drum. I always set the drag of the shoes so there is some drag and you can hear it when you rotate the wheel..thats the scraping sound you hear,just means the shoes are set close to the drum surface so the barke is instantaneous when applied..no differnt than a car or truck brake.

olddog · Apr 8, 2009

The "Dexter" type electric brakes are not "self-adjusting" but instead...
You have to adjust them yourself
very similar to the years before "self-adjusting" brakes. Reach in thru a hole in the backplate with a "spoon" and run the star-adjuster up tight and then back off. The magnets are not adjustable but are held loosely against the face of the drum with a weak spring on the lever. Voltage applied to the magnets makes them try to "stick" to the rotating drum,
moving the lever and spreading the bands;
thus appling the brakes.
Most trailer brakes suffer from either rust/seizure or worn too loose beyond the limits of the lever throw.

Trailer brakes

37 chief

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Dutchman

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37 chief

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Michael Soldan

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Michael Soldan

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olddog

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