How Car Trailer Brakes Work

How Car Trailer Brakes Work

Whether you’re getting ready to kick off a road trip or hauling equipment to a job site, safe towing on the road is critical. Statistically, only 12-15% of a trailer’s weight weight is borne on the hitch, with the rest of the weight being carried by the trailer itself. When braking, a lot of power is needed to slow the trailer down, and this is usually done by the trailer braking system.

Types of Trailer Braking Systems

Trailer braking systems can usually be categorized into two types: surge brakes and inertia brakes. These two types of brakes are based on different principles and have their advantages and disadvantages.

Surge Brakes

This type of braking, also known as surge actuators, operates primarily on hydraulic principles. When the tractor decelerates, the forward motion of the trailer causes hydraulic surges, thereby achieving braking effects.
surge brakes


  • Simple to use: it requires no additional power or controllers and is triggered by inertial motion between tractor-trailers. Operation is relatively simple.
  • Economical: It doesn’t require electric components or controllers, resulting in lower costs for installation and maintenance.
  • Wide applicability: Commonly found in small or medium-sized car trailers. Their lengths typically range from 8 to 20 feet, with a load capacity of approximately 1,000 to 7,000 pounds.


  • Relatively weak braking capability: Surge brakes have relatively weak braking power compared to electric brakes. They may not be strong enough during emergency braking, or on large trailers.
  • Inability to adjust braking force: Since surge brakes are triggered by inertia between the trailer and the tow vehicle, the braking force cannot be adjusted or customized on demand like electric braking systems.

Electric Trailer Brakes:

Electric trailer brakes are implemented by electrically driven electromagnets to achieve braking, and the braking force of the trailer can be adjusted through a controller. This allows the braking force of the trailer to be adjusted according to different road conditions, vehicle speeds, and load situations.
Electric Trailer Brakes


  • Powerful braking force: Electric Trailer Brakes, powered by electricity, provide powerful braking force, suitable for medium to heavy-duty vehicle trailers. This includes trailers over 16 feet in length, with load capacities typically ranging from 3,500 pounds to 10,000 pounds, and some heavy-duty trailers capable of carrying loads exceeding 20,000 pounds.
  • Adjustability: The braking force can be adjusted according to different road conditions, loads, etc.


  • Higher cost: Electric trailer brakes involve electrical components and controllers, so they typically incur higher costs for installation and maintenance.
  • Higher complexity: Compared to surge brakes, the operation and maintenance of electric trailer brakes are relatively complex. If one is not familiar with electrical systems, more learning and skills may be required.

Why are trailer brakes important?

Understanding the types of brakes, let’s delve into why trailer brakes are crucial. They primarily serve the following functions:

  1. Safety: Trailer brakes provide additional braking force in emergencies, helping drivers to decelerate faster and thereby reducing the likelihood of accidents. This is especially critical during long-distance travel or high-speed driving.
  2. Stability: Trailer brakes offer additional braking power, effectively reducing swaying and instability during braking. This enables drivers to quickly control the vehicle when faced with sudden stops or sharp turns.
  3. Braking Efficiency: Car trailer brakes deliver more uniform and reliable braking performance, whether on flat roads, steep slopes, or heavy or light loads. This reliability helps maintain the stability of the braking system and extends its lifespan.
  4. Emergency Braking: Car trailer brakes play a crucial role in emergencies. They provide extra braking force, helping drivers to stop the trailer more quickly, reducing the risk of accidents and effectively protecting the safety of the driver or others.

How to maintain the braking system?

Maintaining the braking system is essential, as severe wear can reduce the performance of the braking system. Regular maintenance ensures they are in optimal condition, ensuring our safety while extending their lifespan.

Regular Inspection

  • Brake Cables and Linkages: Inspect the brake cables and linkages for signs of wear, rust, or damage, and ensure they are securely fastened and not excessively stretched, as this can affect the responsiveness of the brakes.
  • Brake Assemblies: Check the brake shoes or pads for even wear; uneven wear may indicate issues with the braking system. Additionally, inspect the brake drums or rotors for signs of overheating or scoring.
  • Mounting Hardware: Inspect the mounting hardware of the brake components, tighten any loose bolts or nuts, and replace any corroded or damaged hardware.
  • Brake Actuator: Check the brake actuator for leaks or damage, ensuring smooth engagement and disengagement when the towing vehicle’s brakes are applied and released.


  • Cables and Linkages: Apply high-quality lubricant to the pivot points and moving parts of the brake cables and linkages to reduce friction and ensure smooth movement.
  • Brake Cam and Adjuster: Lubricate the brake cam and adjuster mechanisms to prevent them from seizing or binding, helping maintain proper brake shoe alignment and ensure consistent braking force.
  • Brake Pivot Points: Apply lubricant to the pivot points of the brake shoes or pads to ensure they can move freely within the brake assembly.

Common Brake Problems and Solutions:

Poor Braking Performance:

Issue: The trailer brakes are not effective, resulting in longer braking distances.

Solution: Check if the brake drums or rotors are smooth and ensure good contact between the brake shoes or pads and the drums or rotors. Additionally, inspect the brake adjuster to ensure proper adjustment for optimal braking performance.

Brake Drum Overheating:

Issue: The brake drums become overheated during use, potentially leading to reduced braking effectiveness or brake damage.

Solution: Check for signs of overheating in the brake drums, which may result from excessive contact between the brakes and drums or prolonged brake usage. Ensure there is adequate clearance between the brakes and drums for heat dissipation and take breaks to avoid continuous prolonged braking.

Brake Failure:

Issue: Complete loss of braking effectiveness, unable to slow down the trailer.

Solution: Firstly, inspect the hydraulic lines and connections of the brake system for leaks or damage. If there are leaks or damage, promptly repair or replace them. Secondly, check if the brake cables and linkages are broken or disconnected, and if so, repair or replace them immediately.

Brake Noise:

Issue: Sharp noises emitted from the brakes during use.

Solution: Check if the surface of the brake drums or rotors is smooth and ensure that the brake shoes or pads are not abnormally worn or obstructed by foreign objects. If any abnormalities are found, promptly clean or replace them.

Purchase a Car Trailer with Brakes Now!

Three Horses Trailer is dedicated to providing users with high-quality trailers, along with customized services. You can choose the type of brakes for the trailer, as well as the material, size, color, and more. If you are interested in buying a car trailer, feel free to contact us anytime!

Custom Your Trailer

Don’t hesitate to get in touch with us to explore our trailer and discuss how we can meet your unique requirements.

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