What Are Trailer Brakes & Why Do You Need Them?

When you and your trailer are rolling along the road, you want to be sure of one thing: that you will be able to stop when you need to. Successfully braking while towing a trailer is not only a matter of keeping your cargo intact but also keeping you and those around you safe. In this guide, we will look at how trailer brakes work, the different types you may encounter, tips for towing, and maintenance considerations.  

1. What Are Trailer Brakes?
2. Purpose of Trailer Brakes
3. Parts of a Trailer Braking System
4. Types of Trailer Brakes and How They Work
5. Tips for Towing with Trailer Brakes
6. Maintenance Considerations for Trailer Brakes

As you might have already guessed, trailer brakes are installed in the undercarriage of a trailer and activate whenever the tow vehicle brakes. They help your trailer slow down in a timely and safe manner, rather than having your tow vehicle’s brakes do all the work. 

You might be wondering: why does my trailer need brakes? Can’t I just use my tow vehicle’s normal brakes? There are several good answers to those questions.

Firstly, there are many situations where brakes for your trailer are required by law. While the exact rules depend on your trailer’s weight and which state you are in, a general rule is that trailers weighing 1,500 pounds or more are required to have brakes. Check your local regulations to see what exactly your trailer needs. 

Even if you are not technically required to use trailer brakes, you’ve still got plenty of reasons for why they come in handy. Trailer brakes improve your overall braking ability, ensuring that you’ll stop with plenty of space to spare. They evenly distribute the braking force across both the vehicle and the trailer, smoothing out the braking process and preventing trailer sway or other losses of control. 

Finally, trailer brakes take some of the pressure off of your tow vehicle, reducing the wear and tear on the vehicle’s brakes. This not only extends the life of your vehicle’s brakes but prevents any accidents resulting from the brakes becoming overloaded and failing on the road. 

Let’s look at some of the key components of trailer brakes so you can get a better idea of how these helpful devices work. Note that not all of these parts are included in every trailer brake system – it depends on the individual trailer and what type of brake system you’re using (we’ll discuss those in a minute). 

The brake assemblies perform the braking action against your spinning wheels. Located behind the wheel assembly, these include the brake pads, a drum or rotor, and other hardware. 

The wiring system connects with your vehicle and allows electrical signals to be sent to your trailer. With this setup, your trailer brakes will activate when your vehicle brakes, smoothing out the braking process. You will need to make sure your wiring system has a 6 or 7-pin cable; any less than that, and your wiring system will only be able to work your trailer’s lights. 

Installed inside the tow vehicle’s cab, a brake controller has two valuable purposes. 1) It allows you to adjust the braking force of your brake system through two metrics: maximum output (the maximum amount of power the controller will apply to the brakes) and sensitivity level (how aggressively the controller will apply the brakes). This way, you can be certain that your trailer brakes will respond quickly but smoothly. 2) Brake controllers come with a switch that lets you control the trailer brakes independently of your vehicle’s brakes. This is especially useful when towing heavy loads or driving downhill, maximizing your control and your safety. 

Brake controllers can be divided into two types: time-delay and proportional. Time-delay controllers apply an increasing amount of braking power over a fixed period of time, which you can adjust as needed. Proportional controllers use an accelerometer to detect changes in inertia; when you brake, they apply proportional braking power to your trailer. They are a little more expensive than time-delay controllers, but they’re also more precise. 

The actuator resides on the trailer tongue and responds to changes in momentum. When you begin to slow down, it activates the hydraulic pressure that triggers the brakes. 

The hydraulic lines and fluid transmit pressure and activate the brakes. 

Short for anti-lock braking system module, this device prevents the wheels from locking up while braking, avoiding skidding and other losses of control. 

The breakaway system is a crucial component of your trailer’s brake system – and hopefully one you will never have to use. In the event that your trailer becomes detached from your tow vehicle on the road, the breakaway system will activate the brakes and bring the trailer to a stop. The system includes a breakaway cable connecting the trailer with the tow vehicle – if the cable becomes disconnected, it will activate the brakes – and an onboard battery to power the brakes in the event of an electrical failure. 

Now, let’s explore the different types of trailer brakes you may encounter. Each kind of trailer brake works differently, so we’ll discuss their methods too. 

The most common type of trailer brakes, electric brakes use electrical signals from the tow vehicle to activate the brakes as needed. They are popular for good reason: they’re easily adjustable, simple to use, compatible with most vehicles, and offer precise control over the brakes. The only big negative is that you need an electrical connection between your vehicle and trailer for them to work.

How They Work: When you press down on your brake pedal, the brake controller installed in your tow vehicle sends a signal through your vehicle’s electrical system and into your trailer’s wiring system. The signal travels to the brake assembly, where an electromagnet activates and presses the brake pads against the drum or rotor, creating friction and bringing the wheel’s spinning to a stop. 

Surge brakes are activated by the forward momentum of the trailer itself pressing against an actuator. These are simple mechanisms that don’t necessarily require electrical connections to function. This makes them ideal for boat trailers (you wouldn’t want to give yourself a zap while launching your boat!). 

However, surge brakes do not offer the same level of control as electric brakes, and they are not as good for heavier loads. You might also find your surge brakes activating when you’re rolling down a hill – if your trailer is heavier than your vehicle, it will go downhill faster, pressing against the actuator. This unnecessary braking increases the wear-and-tear on the trailer brakes, shortening their lifespan. 

How They Work: When you apply the brakes and slow your vehicle, your trailer’s forward motion pushes it against the actuator located on the trailer tongue. The actuator compresses and creates pressure in the trailer’s hydraulic lines. The hydraulic fluid transmits the pressure to the brake assembly, activating the brakes and slowing the trailer. 

Hydraulic brakes are very similar to surge brakes, both using hydraulic pressure to activate the brakes. The difference is that hydraulic brakes require a separate hydraulic brake system within the trailer. This distinction allows them to handle larger loads and rougher roads better. 

How They Work: The hydraulic brake system’s master cylinder is connected to the tow vehicle’s brake pedal; when you apply the brakes, the hydraulic fluid within said cylinder is pressurized. The fluid runs through the brake lines and to the brake assemblies, activating the brakes and slowing the trailer. 

Air brakes use pressurized air to activate the brakes. They are typically only used for commercial trailers and heavy-duty vehicles, offering precise control and powerful braking capabilities for heavy loads across great distances. 

How They Work: When you apply the brakes, compressed air is released from reservoirs. The air pressure is transformed into mechanical force by brake chambers. This force presses the brake pads down and slows the trailer. 

Even if you have the most reliable, well-tuned trailer brakes in the world, safely stopping a trailer is not merely a matter of slamming your foot on the brake pedal. Here are some tips for staying safe on the move (and when you want to stop moving): 

1. Familiarize yourself with your braking system and how it works.
If you have electric brakes, make sure that your brake controller is properly installed and calibrated. If you have surge brakes, know that you might experience some unwanted braking while going downhill. The more you know about your trailer brakes, the better you will be able to use them. 

2. Practice braking in a safe, secluded location, such as a parking lot.
This will give you a better idea of how well your brakes work and how it will feel when you brake. Make any necessary adjustments. Take the opportunity to test your breakaway system to ensure it works. 

3. Practice braking on the road.
The most important thing to remember is that stopping a trailer is going to take longer than stopping an unhitched vehicle; the trailer’s weight and momentum will carry you further no matter how hard you brake. Give yourself plenty of time to come to a stop and begin braking sooner than you normally would. Keep an eye out for potential problems and maintain a safe distance between you and your fellow drivers. 

4. Remember to stop gradually whenever you can.
Braking sharply creates increased wear on the brakes, reducing their lifespan. If you want to keep your brakes in good shape, treat them kindly!

To finish off, let’s discuss how to keep your trailer brakes in good shape. 

You should take time once a year to visually inspect your entire brake system. Look for any worn or loose parts, replacing them if needed. 

Pay special attention to the brake pads, the components of the brake system that press against the spinning rotor and stop the wheel. The friction wears the brake pads down over time, so you will likely need to replace them on occasion. If your brakes start making odd noises or vibrating when you brake, worn brake pads may be the culprit. 

Depending on what type of trailer brake system you use, you will need to consider specific kinds of maintenance. If you use electric brakes, examine the trailer wiring system for any kinks or worn wires and check the electromagnets for uneven wear, replacing them as needed. 

If you have surge or hydraulic brakes, inspect the brake lines for any kinks or damage. Check that the hydraulic fluid is at proper levels. Look for any leaks in the cylinders, repairing or replacing them as needed. 

If you have air brakes, examine the system for any air leaks. Replace the filter if it becomes clogged with debris. 

Don’t forget to make sure your breakaway system is working! Check the battery for sufficient power levels. You can also test the system by disconnecting the breakaway cable and then attempting to tow your trailer. If the trailer doesn’t budge, everything’s working like it should! 

Whether you’re helping a friend move or heading out for a cross-country adventure, safety should be your number one priority when towing a trailer. Trailer brakes grant you improved braking ability and more control. 

Disclaimers: These photographs, recommendations, and approximations are intended for demonstration purposes only and do not reflect the specifications of any particular tow vehicle, recreational vehicle, or trailer. Always consult the manufacturer’s Owner's Manual.