Semi Truck Trailer Brakes

Although the regulations vary, in most states trailer brakes are required for trailers with a Gross Trailer Weight (GTW) of 3,000 lbs. or more. Besides being the law, trailer brakes are common sense: forcing the brakes on the tow vehicle to stop the vehicle along with an additional 3,000 lbs. or more will only result in increased stopping distance and additional stress and wear on the brakes, which could be dangerous in an emergency situation. No matter what type of brakes you have on your trailer, surge or electric, drum or disc, we have the parts to ensure safe and reliable stops.

Because they are regularly immersed in water when launching and retrieving a boat, hydraulic surge brakes are the type most often found on boat trailers. With surge brakes, the entire braking system is self-contained within the trailer and no hydraulic or electrical connection to the tow vehicle is needed. An actuator mechanism within the trailer coupler contains a hydraulic master cylinder. When the tow vehicle brakes, the trailer’s inertia pressurizes the brake fluid in the master cylinder, forcing it out through the brake lines to the drum or disc brake assemblies.

Hydraulic drum and disc trailer brakes are similar to those on cars and trucks. Drum brakes have shoes lined with friction material secured to a backing plate by hold-down springs, and actuated by a hydraulic cylinder. When the brakes are applied, the brake linings press against the friction surface of the brake drum, which encloses the assembly and attaches to the hub, turning with the wheel. Return springs retract the shoes after brake application. A disc brake assembly includes the rotor, friction pads, and caliper. The rotor is mounted to a hub and turns with the wheel, and the pads are mounted in the caliper that straddles the rotor. When the brakes are applied, hydraulic pressure forces the caliper piston outward, clamping the brake pads on both sides of the rotor.

Electric-Over-Hydraulic brakes are an alternative to pure hydraulic surge brakes that can provide better braking performance. While hydraulic brakes can provide better stopping power than electric brakes, there can be a momentary delay between the time the tow vehicle’s brakes are applied and the hydraulic actuator applies the trailer brakes, plus hydraulic surge actuators typically have to be locked out when the vehicle and trailer are backed up. An electric-over-hydraulic actuator mounts to the trailer and is wired to a trailer brake controller inside the vehicle and connected to the trailer’s hydraulic brake lines. With electric-over-hydraulic actuation you get the superior control and response of the electric brake controller with the harder stopping capability of hydraulic brakes.

Electric brakes are the most common type used on all other trailers. Although actuation is electric, the actual braking is done by shoes and drums just like those on boat trailers and many cars and trucks. However, instead of a hydraulic cylinder applying force to the brake shoes, they’re actuated by magnets. When you step on the brake pedal, electric current is applied to the magnet inside each brake assembly, causing it to be attracted to the metal brake drum. The friction of the magnet against the drum rotates the magnet, which is connected to an actuating lever that in turn pushes the brake shoes against the drum. Voltage is sent through a brake controller mounted inside the tow vehicle, which regulates the amount of brake force using time-based or inertia-based activation.

The best way to ensure your trailer brakes deliver reliable service is to inspect them regularly, especially at the beginning of the season. Check the friction lining thickness, and the condition of the hardware and drum/disc friction contact surfaces. And depending on the type of system check the electrical connections and magnets or hydraulic system and actuator. We have all the parts you need to keep your trailer brakes in top shape, including brake shoes and pads, hydraulic actuators, hardware, bearings, grease seals, and bearing protectors/lubricators. We offer all of the most popular types and sizes, including complete drum or disc assemblies, and complete hydraulic surge and electric brake systems.