Camping trailers, enclosed cargo trailers and car haulers are all examples of trailers that may use electric drum brakes. An electronic brake controller mounted in the tow vehicle applies the trailer brakes automatically when the tow vehicle's brake pedal is depressed. The controller senses the amount of brake pedal pressure, the rate of deceleration and vehicle speed in determining how much pressure is applied to the trailer brakes. The electric drum brakes on the trailer must be adjusted properly for the brake controller to do its job; otherwise, you could have a handful when trying to stop a heavy rig.
Raise one wheel at a time by placing a hydraulic jack under the axle and pumping the jack handle until the tire is off the ground. Chock the tires on the other side of the trailer to prevent movement. Place a jack stand under the axle of the wheel you have raised within a few inches of the brake backing plate. Lower the hydraulic jack so that the axle is resting on the jack stand.
Crawl under the trailer and locate the rubber access plug on the brake backing plate on the backside of the wheel and tire near the axle. Pry the plug out with a flat-tip screwdriver and place it aside.
Rotate the tire as if the trailer were being towed in a forward direction with one hand. Insert a flat-tip screwdriver in the access hole in the brake baking plate with the other hand and rotate the notched brake adjusting wheel in a clockwise direction until you feel braking resistance on the tire.
Back off the brake adjusting wheel by turning the flat-tip screwdriver counterclockwise one notch at a time until the tire rotates forward with very little force. Remove the screwdriver from the access hole. Push the rubber plug back into place until it is fully seated. Raise the axle with the hydraulic jack and remove the jack stand. Lower the hydraulic jack until the tire is on the ground, then remove the jack from under the trailer.
Repeat the entire procedure to adjust all remaining drum brakes on the trailer.
