Mechanical vs Electric vs Hydraulic Trailer Brakes

When it comes to trailer braking systems, there are two main types: indirect and direct.

Indirect brakes use a mechanism that relies on the trailer's momentum to activate the braking system. When the towing vehicle slows down, the trailer continues to move forward until that movement activates a brake system that applies pressure to the trailer's brakes.

Direct brakes apply braking force through a direct connection between the towing vehicle and the trailer’s braking components. In these systems, the braking signal from the towing vehicle is directly communicated to the trailer. These systems offer immediate, precise braking control, making them ideal for larger, heavier trailers or situations requiring strong stopping power.

These brakes are further classified into four subtypes:

Indirect: mechanical override or surge brakes
Direct: electric brakes, electric over hydraulic brakes and hybrid

Each subtype can either come in the form of drum brakes or disc brakes, and has its own unique mechanism.

Let's take a closer look at each type to further understand the differences between mechanical, electric, hydraulic and hybrid brakes.

Mechanical Trailer Brakes

Often referred to as overrun or override brakes, mechanical trailer brakes use the trailer’s momentum to activate the brakes through a mechanical linkage or cable system.

Mechanical brakes operate using a sliding spring mechanism attached to the trailer’s drawbar. When the towing vehicle brakes, the trailer will “overrun” or continue to move towards the towing vehicle due to inertia, and consequently, compress the spring mechanism that is in between the towing vehicle and the trailer.

This compression automatically triggers the trailer brakes pulling on the brake cables attached to the trailer's brake system. These cables are connected to the brake pads. The tension in the brake cables causes the brake pads to press against the brake drum or disc which is attached to the wheels of the trailer, creating friction and slowing it down.

Once the towing vehicle starts moving again, the spring decompresses, deactivating the brakes, and the trailer resumes movement with the towing vehicle.

Here's an example of a mechanical trailer brake. The video talks about this mechanism a bit:

Common Uses

Mechanical brakes are often used all-purpose trailers as well as tiny homes, caravans, plant trailers and, tipper trailers.

Advantages

• Simple design: Mechanical brakes have a straightforward design, making them easy to understand and work on.
• Ease of maintenance: Because of their simplicity, mechanical brakes are generally easy to maintain, adjust and repair.
• No need for power: Mechanical brakes do not require any external power source or Bluetooth, making them reliable in situations where electricity or hydraulic fluid might not be available.
• Low cost: They are affordable and replacement parts are often inexpensive and readily available.

Electric Trailer Brakes

An electric brake uses an electromagnet to activate the brake pads in the wheels. These brakes are triggered by the vehicle operator either by a brake controller in the towing vehicle or a signal being sent to a brake controller on the trailer. The brake controller then activates the brakes in the hubs.

When the driver steps on the towing vehicle’s brake pedal, the brake controller sends an electric current to the magnet inside the trailer brakes. This creates an electric field that activates the magnet and allows it to, in a series of movements, push the brake shoes against the brake drum or disc that is attached to the wheel hub. This prevents the wheel from spinning and consequently stops the trailer from moving.

When the brake pedal is released, the brake controller stops sending an electric signal to the trailer brakes, effectively cutting the power off. This disengages the brake pads and allows the trailer to move with the towing vehicle again.

Here’s an example of an electric brake:

 

Common uses

Electric brakes are frequently used in utility trailers, cargo, horse, flatbed, agricultural and equipment trailers.

Advantages

• Cost effective: Electric brakes are usually a cheaper baking option.
• Vehicle integration: Many modern trucks an utes have factory fitted brake controllers that make applying the trailer brakes an integrated experience.
• Simple maintenance: Electric brakes are generally easier to maintain than hydraulic brakes due to having fewer components.

Disadvantages

• Dependence on electrical system: Electric brakes depend on a battery and electrical system, which can fail. If the electrical system malfunctions, the brakes may not work properly.
• Adjustments: Electric brakes need to be adjusted depending on the load of the trailer.
• Vehicle pairing: The trailer may be paired with a specific wireless brake controller in the tow vehicle, limiting the number of towing options.

Hydraulic Trailer Brakes

Hydraulic trailer brakes utilize hydraulic fluid to transmit force from the brake pedal to the brake components. When you press the brake pedal, it pushes hydraulic fluid through a series of hoses and cylinders, which then apply pressure to the brake pads or shoes.

Image by KDS444 - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=24878290

Common Uses

Hydraulic brakes are widely used in cars, trucks, and other heavy-duty vehicles. In terms of trailers, they are often used on livestock, dump, heavy cargo, contsruction and heavy-duty utility/equipment trailers, although smaller trailers can also use hydraulic brakes for superior braking power.

Advantages

• Strong braking power: Hydraulic brakes provide strong and consistent braking power, making them ideal for high-speed and heavy-duty applications.
• Effective under various conditions: Hydraulic brakes are effective under a wide range of conditions, including wet and muddy environments.
• Self-adjusting: Many hydraulic brake systems are self-adjusting, meaning they automatically compensate for wear and tear on the brake pads.

Disadvantages

• Complexity and cost: Hydraulic brake systems can be more complex and expensive to repair compared to mechanical brakes. They require specialized knowledge and tools for maintenance.
• Potential for leaks: Since hydraulic brake systems use hydraulic fluids to activate the brakes, they can sometimes leak. When the fluid leaks, the brake’s hydraulic pressure will be reduced, which translates to weaker brakes.

Hybrid Trailer Brakes (Electric-over-Hydraulic Brakes)

Hybrid trailer brakes, also known as electric-over-hydraulic (EOH) brakes, combine electric and hydraulic systems to provide braking power for trailers.

Electric-over-hydraulic (EOH) brakes connect to tow vehicles through a brake controller and a wiring harness, which sends an electric signal to the trailer. The signal activates an electric actuator on the trailer, powering a pump to generate hydraulic pressure. This pressure flows through brake lines to the trailer’s brakes, where it applies friction to slow or stop the trailer. The brake controller adjusts the signal based on how hard the driver presses the brake pedal, providing proportional braking for smooth and controlled stops.

Common Uses

Hybrid brakes are typically used on boat trailers or those requiring more braking power, that’s why they are mostly used on big equipment or vehicle transporters, animal transporters, utility and flatbed trailers. They are also used for hauling large boats as the combination of electric and hydraulic braking provides better control.

Advantages

• Enhanced Braking Power: The hydraulic component provides strong, consistent braking power, ideal for heavy-duty trailers or trailers with large loads.
• Proportional Braking: The system offers proportional braking, meaning the braking force is adjusted in sync with the braking effort of the tow vehicle, offering smoother and more controlled stops.
• Improved Performance: Hybrid braking systems usually perform better in demanding conditions such as steep inclines or when carrying heavy loads.
• Self-Adjusting: The system is typically self-adjusting, so it maintains consistent braking performance without the need for manual adjustments.

Disadvantages

• Complexity: Hybrid brake systems are more complex than purely mechanical or electric brakes, requiring both electrical and hydraulic components, which can increase the potential for malfunction.
• Cost: These systems are typically more expensive to install and repair than simpler braking systems.
• Exposure to Water: While hydraulic components are durable, they can still be vulnerable to corrosion, especially in saltwater environments, unless sealed properly.
• Compatibility: Hybrid systems require a specific brake controller in the tow vehicle, which may not be available in all vehicles or could require additional setup.

Other Trailer Brakes

Breakaway System

A breakaway trailer system is a safety feature designed to automatically apply the trailer’s brakes if the trailer becomes detached from the tow vehicle. The system includes a breakaway switch attached to the trailer and a cable that connects to the tow vehicle. If the trailer separates from the tow vehicle, the cable pulls the switch, activating the brakes to prevent the trailer from becoming a runaway hazard.

Parking Brake

A parking brake, also known as an emergency brake or handbrake, is a braking system designed to hold a vehicle or trailer stationary when it is not in motion. It is typically used to prevent rolling when the tow vehicle or trailer is parked, especially on inclines. In trailers, the parking brake is activated manually, usually by a lever or handle, and is often required by law for trailers over a certain weight. It works independently of the regular braking system and is designed to ensure the trailer remains safely in place until the driver is ready to resume towing.

Choosing the Right Brake System

When choosing the right braking system for your trailer, your range of options will depend on your specific needs and the type and weight of load you are towing.

In New Zealand, the appropriate trailer brake system is generally determined based on the gross laden weight (GLW) of the trailer. The law requires that any light vehicle and trailer combination must be able to stop within 7 meters when traveling at 30 km/h.

Here are the key guidelines for determining the required braking system for trailers:

Type of brake	Gross laden weight of the trailer
	2,000 kg or less	2,001–2,500 kg	2,501-3,500 kg
Service brake	Not required but, if fitted, must act on each wheel of at least one axle.	Required: May be either direct or indirect.	May be either direct or indirect, and must act on each wheel of at least one axle (the indirect service brake must comply with UN/ECE Regulation No.13). Note: A compliant brake system requires a brake on each wheel of the trailer.
Parking brake	Not required.	Not required.	Required, and must act on at least one complete axle.
Breakaway brake	Required unless fitted with an appropriate coupling and safety chain (the safety chain must be of sufficient strength to hold the trailer secure under all conditions of road use).	Required, unless fitted with an appropriate coupling and two safety chains.	Required, unless fitted with an appropriate coupling and two safety chains. Note: If a breakaway brake is fitted, safety chains are still recommended but not required.

Source: “Guide to safe loading and towing for light vehicles.” NZ Transport Agency,https://www.nzta.govt.nz/resources/glovebox-guide-safe-loading-towing/guide-safe-loading-towing

Trailers above 3,500 kg are considered heavy trailers and are regulated under heavy transport rules and require a Certificate of Fitness (COF). These trailers must have direct service brakes on every axle, as inertia-based controllers are not allowed on heavy trailers. At least half of the axles need a handbrake for added safety. A breakaway system is mandatory to apply the trailer's brakes automatically in the event of detachment, and the braking system must achieve 50% efficiency and meet the stopping and handbrake performance standards for trailers over 2,501 kg.

Get Expert Advice from Treadway

Understanding the differences between these braking systems can help you make an informed decision and ensure that you have the right brakes for your needs.

But if you are still unsure, don’t fret! Our team is only a call or email away to answer your questions and help you choose the right brakes for your trailer.

Ask us now and start worrying less on the road.