How Do Magnetic Trailer Brakes Work?

Types of trailer brakes

Magnetic trailer brakes, commonly referred to as electric trailer brakes, are one of the three types of trailer brakes. The other two are hydraulic surge brakes and air brakes. Magnetic trailer brakes are used on all types of trailers except semi-trailers and boat trailers. Electric trailer brakes are very simple to retrofit, and are the easiest to maintain of all the trailer brakes.

Magnetic trailer brake controls

Magnetic trailer brakes work in conjunction with a brake controller, an electronic control box in the tow vehicle. This controller is wired to the brake light switch and to the battery. When the brake pedal in the tow vehicle is depressed, power is supplied to the brake controller, which switches modulated battery power to the magnetic trailer brakes. There are controls on the box to regulate how much battery power the electric brake receives. This determines how much braking power the trailer has. Without this adjustment, the trailer brakes would either lock up with a light load, or not have enough braking power for heavy loads.

What makes them work

The magnetic trailer brake is applied by means of an electric magnet within the brake mechanism. This magnet is attached to bottom of an arm which pivots at its top end. The arm is also linked to the brake shoes. When the magnet is energized, it is attracted to the spinning brake drum, causing the arm to move forward, applying the brakes. The adjustments on the brake controller determine how much current is supplied to the electric magnet, which in turn determines the strength of the attraction to the brake drum. The stronger the attraction, the larger the force that is applied to the brakes, and the harder the shoes contact the brake drum.