How Do Trailer Brakes Work? (Full Guide)

How Do Trailer Brakes Work

Do you know how do trailer brakes work? Well, you are at the perfect place to find the answer to such a question.

There are a variety of different brake types that you can have installed on your trailer. Three, in fact, which include:

  • Mechanical trailer brakes
  • Hydraulic trailer brakes
  • Electric trailer brakes

On this page, we are going to go through each of these types.

We are also going to give you a brief idea as to which brake type may be the best choice for your trailer. 

How Do Mechanical Brakes Work?

If you have a lighter trailer, then chances are that it will have mechanical brakes on it. These are easily some of the most popular trailer brakes around. Not only are they affordable, but they are highly effective. 

Mechanical trailer brakes are simple. They are formed of just a couple of components.

Attached to the hitch area will be a spring mechanism. As long as your trailer is traveling at the same speed as your vehicle (and is straight), this spring mechanism just sits there not doing a whole lot.

However, once the vehicle begins to slow down, the spring mechanism will ‘detect’ that the trailer is traveling faster than the vehicle.

When the spring mechanism detects that the trailer is traveling faster than the vehicle, it will engage. When it engages, the brake cables will also engage.

The brake cables will tighten up which, in turn, is going to push the brakes against the trailer’s wheels, slowing the trailer down at the same time.

Once the trailer is traveling at the same speed as the vehicle, the spring will disengage, and the trailer will stop slowing down.

As we said, the mechanism is incredibly simple. However, it really is effective.

There are not a whole lot of components in place and, assuming the system has been properly maintained, slowing down should be an absolute breeze.

It is worth pointing out that this system isn’t quite so effective if the trailer isn’t straight. A trailer that has jack-knifed even a little bit may be seen as traveling faster than the vehicle, and thus the brakes engage when they really shouldn’t be engaging.

However, thankfully, if you learn how to drive your vehicle properly, this isn’t something that should really pose too many problems for you. 

Read also >> How To Set a Trailer Brake Gain? 6 Easy Steps (Explained)

How Do Hydraulic Trailer Brakes Work?

Hydraulic brakes are a step above mechanical brakes. They are designed for slightly heavier trailers, and they have superb braking power. However, they can be a bit tricky to use. This is because hydraulic brakes often don’t engage right away.

This means that slowing down can be a little bit difficult. To demonstrate this, let’s tell you a little bit about how they work.

Hydraulic brakes follow roughly the same system as mechanical trailer brakes. This means that there is absolutely no electrical system in place.

The same principle applies. Although, rather than there being a spring mechanism in place, there is a ‘surge actuator’. This little component is constantly checking to see whether the vehicle is traveling at the same speed as the trailer.

 If it detects that the trailer is going faster than the vehicle, then the hydraulic braking system will kick in.

A hydraulic braking system is comprised of a series of pipes and valves. It is a completely sealed unit, with hydraulic fluid in the system. When the surge actuator detects that the trailer is going too fast, it will release the hydraulic fluid.

This hydraulic fluid will then be pumped through the system where, eventually, it is going to end up at the brakes.

The hydraulic fluid will put pressure on the brakes, forcing the trailer to slow down. 

Read also >> How Do Hydraulic Trailer Brakes Work? (Simply Explained!)

Read also >> How Much Can You Tow Without Trailer Brakes? (Explained)

A good-quality hydraulic braking system is fantastic at slowing trailers down. In many cases, heavy trailers should have some sort of hydraulic braking system in place. A mechanical braking system just isn’t good enough for heavier trailers.

A hydraulic braking system isn’t without its issues, though. The problem with a hydraulic trailer braking system is the fact that it does take a good while for that fluid to be pumped through the entire system. This means that it can take a while for a trailer with hydraulic brakes to slow down.

This is very much a system that favors coming to a slow and steady stop, rather than hard braking.

When using a hydraulic braking system for the first time, many people find that it can be a little bit difficult to get used to the braking experience.

So, if your trailer uses a hydraulic braking system, you may want to take some time to practice before you head out on the roads. 

How Do Electric Brakes On a Trailer Work?

Electric trailer brakes come in a variety of different ‘styles’. For example, you can get hydraulic electric brakes. We want to focus on electric brakes as a whole here, though. This is because the principle is much the same.

As the name implies, electric brakes run on the electrics in your vehicle. This means that they are a bit trickier to install, but worth it if you plan on using a trailer a lot.

Inside of your vehicle, you will have a gadget known as a ‘brake controller’. On this brake controller, you will be able to control a whole host of braking settings for your trailer e.g. how hard those brakes should be hit, etc.

Although, in most cases, you probably won’t need to play about with the brake controller too much. The only time that you really need to interact with it is if you are regularly changing the weight of the trailer.

The brake controller will be wired into the brake lights of the vehicle. How things are set up beyond this point will differ. For example, some electric trailer braking systems are completely wireless, while others will need some additional wiring in place. In both cases, your trailer is going to need to be hooked up to the electrical outlet on the back of the vehicle.

Read also >> Trailer Brake Controllers: 25 Facts You Should Know (Explained)

Now, whenever the brakes are engaged on your vehicle, the brake lights turn on. When the brake lights turn on, this is a signal for the braking system on your trailer to also activate.

A properly installed electric brakes system is incredibly efficient when it comes to slowing your trailer down.

Because the trailer will automatically brake whenever your vehicle brakes, the uses for an electric braking system are larger than with non-electric brakes.

As we said, mechanical and hydraulic brakes don’t work quite so well when the trailer is at an angle. Neither of them is great at operating off-road either.

However, an electric braking system can be used in most situations. 

What Is The Best Type Of Brake To Use On a Trailer?

This will be dependent on a few things. You will need to think about the weight of your trailer, whether you have the necessary outlets on your vehicle, and how often you are planning on towing with your vehicle.

In most cases, with lighter trailers, a mechanical braking system will be fine. You don’t need anything too extravagant. However, once you start getting into the heavier trailers (especially RVs and the like), then you will want to ensure that there is a hydraulic braking system in place, minimum.

It is much safer for heavier loads. Hydraulic braking systems have a huge amount of braking pressure.

Of course, if you want the best of the best, then you will need electric brakes. While they may require a bit of wiring in, especially if you do not have the set-up already, once they are hooked up to everything, they are the most effective at bringing your trailer to a lower speed.

Although, do bear in mind that there is a lot more that can go wrong with an electric braking system. 

Are Trailer Brakes Easy To Use?

Trailer brakes will always take a bit of getting used to, especially if you are hitting the road with either a mechanical or hydraulic braking system.

You have to remember that trailer brakes are never going to trigger as quickly as your vehicle’s brakes will.

This means that if you are going at a massive speed and suddenly brake, there is a strong chance that your trailer will smash into your vehicle. If you are using trailer brakes, then you need to come to a gradual stop.

This is going to be less of an issue if you are planning on using an electric braking system, but it can still require a little bit of practice. 

How Trailer Brakes Work & How To Inspect >> Check out the video below:


No matter which trailer braking system you use, they will all work in roughly the same way. There will be a small component or device that detects when your vehicle is slowing down.

This gadget or device will then send a signal through to the brakes on the trailer, engaging them.

The brakes will continue to remain engaged until the trailer is traveling at exactly the same speed as the vehicle. 

The best braking system for your vehicle will vary based on the trailer that you are pulling. Heavier loads should always opt for hydraulic or electric brakes. 



Jeff is an automotive technician, technical writer, and Managing Editor. He has held a lifelong passion for cars, with a particular interest in cars like the Buick Reatta. Jeff has been creating written and video content about transportation, automotive, electric cars, future vehicles as well as new, used for more than 18 years. Jeff is based in Boulder, Colorado.

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