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Newnan, GA


Fayetteville, GA

Your Complete Guide to Electric Brakes for Cargo Trailers

Your trailer brakes are designed to work in synchronization with your tow vehicle brakes.  Never use your tow vehicle or trailer brakes alone to stop the combined load.

Your brake controller must be set up according to the manufacturer's recommendations to ensure proper synchronization between the tow vehicle and the trailer.  Additionally, you may have to make small adjustments occasionally to accommodate changing loads and driving conditions.

Proper synchronization of tow vehicle to trailer braking can only be accomplished by road testing. Brake lockup, grabbiness, or harshness is quite often due to the lack of synchronization between the tow vehicle and the trailer being towed, too high of a threshold voltage (over 2 volts), or under adjusted brakes.

Before any synchronization adjustments are made, your trailer brakes should be burnished-in by applying the brakes 20-30 times with approximately a 20 mph decrease in speed, e.g. 40 mph to 20 mph. Allow ample time for brakes to cool between applications. This allows the brake shoes and magnets to slightly “wear-in” to the drum surfaces.

Trailer Wire Size Chart

Number                                  Hitch-to-Axle                       Recommended

Of Brakes                               Distance in Ft                     Minimum Hookup

Wire Size (Cooper)



12 AWG


Under 30

12 AWG



10 AWG


Under 30

10 AWG



8   AWG

Synchronizing Your Trailer Brakes

To ensure safe brake performance and synchronization, read the brake controller manufacturer’s instructions completely before attempting any synchronization procedure.


Before road testing, makes sure the area is clear of vehicular and pedestrian traffic.  Failure to brake safely could result in an accident and personal injury to yourself and/or others. 

Make several hard stops from 20 mph on a dry paved road free of sand and gravel.  If the trailer brakes lock and slide, decrease the gain setting.  Adjust the controller just to the point of impending brake lockup and wheel skid.  

Note:  Not all trailer brakes are capable of wheel lockup.  Loading conditions, brake type, wheel and tire size can all affect whether a brake can lock.  It is not generally considered desirable to lock up the brakes and slide the tires.  This can cause unwanted flat spotting of the tires and could also result in a loss of control.

If the controller applying the trailer brakes before the tow vehicle brakes, then the controller adjustments should be made so the trailer brakes come on in synchronization with the tow vehicle brakes.  For proper braking performance, it is recommended that the controller be adjusted to allow the trailer brakes to come on just slightly ahead of the tow vehicle brakes.  When proper synchronization is achieved there will be no sensation of the trailer “jerking” or “pushing the tow vehicle during braking. 

Maintenance of Electric Brakes

Brake Adjustment

Dexter electric brakes that have a self adjusting feature require no manual adjustment.  Brakes not equipped with this feature can be adjusted by using the following procedure:
Brakes should be adjusted

(1) after the first 200 miles of operation when the brake shoes and drums have “seated” (2) at 3,000 mile intervals, (3) or as use and performance requires.  The brakes should be adjusted in the following manner: 

1. Jack up trailer and secure on adequate capacity jack stands.  Follow trailer manufacturer’s recommendations for lifting and supporting the unit.  Make sure the wheel and drum rotates freely. 


Do not lift of support the trailer on any part of the axle or suspension system. Never go under any trailer unless it is properly supported on jack stands which have been rated for the load.  Improperly supported vehicles can fall unexpectedly and cause serious injury or death.  

2. If equipped, remove the adjusting hold cover, if present, from the adjusting slot on the bottom of the brake backing plate.  

3. With a screwdriver or standard adjusting tool, rotate the star wheel of the adjuster assembly to expand the brake shoes.  Adjust the brake shoes out until the pressure of the linings against the drum makes the wheel very difficult to turn.Note: For drop axles, a modified adjusting tool may be necessary.

4. Then rotate the star wheel in the opposite direction until the wheel turns freely with a slight lining drag.  

5. Replace the adjusting hold cover, if available, and lower then wheel to the ground.  

6. Repeat the above procedure on all brakes.  For best results, the brakes should all be set at the same clearance.  

How to Clean Brakes and Inspect Them

Your trailer brakes must be inspected and serviced immediately if a loss of performance is indicated.  With normal use, serving at one year intervals is usually adequate.  With increased usage, this work should be done more frequently as required.  Magnets and shoes must be changed when they become excessively worn or scored, a condition which can reduce vehicle braking. Clean the backing plate, magnet arm, magnet, and brake shoes.  Make certain that all the parts removed are replaced in the same brake and drum assembly.  Inspect for any loose or worn parts, stretched or deformed springs and replace as necessary.  


Potential Asbestos Dust Hazard!Some older brake linings may contain asbestos dust, which has been linked to serious or fatal illnesses.  Certain precautions need to be taken when servicing brakes: 

1. Avoid creating or breathing dust. 

2. Avoid machining, filing or grinding the brake linings. 

3. Do not use compressed air or dry brushing for cleaning (dust can be removed with a damp brush).

Brake Lubrication

Before reassembling, apply a light film of grease or anti-seize compound on the brake anchor pin, the actuating arm bushing and pin, and the areas on the backing plate that are in contact with the brake shoes and magnet lever arm.  Apply a light film of grease on the actuating block mounted on the actuating arm. 


Do not get great or oil on the brake linings, drums or magnets. 


Your electric brakes are equipped with high quality electromagnets that are designed to provide the proper input force and friction characteristics.  Your magnets should be inspected and replaced if worn unevenly or abnormally.  As indicated below, a straightedge should be used to check magnet condition.  For best results, the magnet should be flat.  

Even if wear is normal as indicated by your straightedge, the magnets should be replaced if any part of the magnet coil has become visible through the friction material facing of the magnet.  It is also recommended that the drum armature surface be refaced when replacing magnets (see section on Brake Drum Inspection).  Magnets should also be replaced in pairs – both sides of an axle.  Use only genuine Dexter replacement parts when replacing your magnets.  

Brake Shoes and Brake Linings

A simple visual inspection of your brake lining will tell if they are usable.  Replacement is necessary if the lining is worn to 1/16” or less.  Shoes contaminated with grease or oil, or abnormally scored or gouged should also be replaced.  Hairline heat cracks are normal in bonded linings and should not be cause for concern.  When replacement is necessary, it is important to replace both shoes on each brake and both brakes of the same axle.  This will help retain the “balance” of your brakes. 


Potential Asbetstos Dust Hazard!Some older brake linings may contain asbestos dust, which has been linked to serious or fatal illnesses.  Certain precautions need to be taken when servicing brakes:

1. Avoid creating or breathing dust.

2. Avoid machining, filing or grinding the brake linings. 

3. Do not use compressed air or dry brushing for cleaning (dust can be removed with a damp brush). 

After replacement of brake shoes and linings, the brakes must be re-burnished to seat in the new components.  This should be done by applying the brakes 20 to 30 times from an initial speed of 40 m.p.h., slowing the vehicle to 20 m.p.h.  Allow ample time for brakes to cool between applications.  This procedure allows the brake shoes to seat in to the drum surface.  

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