# ELECTRIC TRAILER BRAKES: INTRODUCTION



## Eastern Marine (Feb 5, 2015)

Electric brakes are a very common and reliable means to control your trailer while towing. They are used most often used on utility and equipment trailers and RVs. They are controlled with a cab mounted brake controller in the tow vehicle. When the time comes to repair or replace them, there are many choices available. It can be confusing to decide what brakes or parts you need for your trailer.
Parts most often replaced are the shoes and magnets. They wear from use and should be inspected periodically and replaced when needed. Depending on how often you use the trailer will determine how often to inspect them. The shoes are easier to check then magnets. You can just measure the thickness of the shoe to find of they need to be replaced. Magnets are harder to troubleshoot sometimes they quit working or will just get weak over time. To replace the shoes or magnets look at your existing brakes. For the shoes measure the diameter of the drum and the width of the shoe. This should help you to determine the correct shoes. Sometimes different weight capacity brakes will have the same size shoes. When this happens you will use the magnet to determine the correct replacement. Use the wires that come directly out of the magnet the color will determine what exact brake you have.
Replacing the entire brake backing plate is sometimes a more cost effective and easier to install. The new magnet and shoes are already mounted on the backing plate. You just unbolt your existing plate bolt on the new plate hook up your magnet wires and adjust for tension. This eliminates having to take apart and rebuild the old brakes, which can be a difficult job. To determine the correct brake assembly use the methods discussed above for the drum diameter, shoe width, and magnet wire color. Also you are going to count the number of bolts that attach the backing plate to the axle. With this information you should be able to easily determine the correct brake for your axle.
A question often asked is if the brake magnets are polarity specific. The magnets do not have polarity they work like a common resistor. One wire is attached to the power and one is attached to the ground wire. It is recommended to run a common ground wire from the plug to the magnets. The brakes should be wired in parallel, not in series.
Installing brakes on a new trailer or one that doesnÂ’t have brakes is very straightforward. You will need to determine if the axles you have are designed to have brakes. There will be a steel plate called a brake flange, welded to the axle at right angles behind the spindle. This will most often have four or five holes drilled in them. They are critical to install brakes on a trailer. If your axle doesnÂ’t have the flanges installed it is recommended to replace the axle assembly with one that does.


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