Caravan brake controllers: What you need to know

By: Brendan Batty

If you’re planning on towing a caravan or large trailer, there's a good chance you'll need to use a brake controller to, as the name suggests, control the caravan or trailer's brakes.

Brake controllers are a requirement on many large trailers, significantly increasing the safety of your towing combination. If you're new to towing, or you're planning a caravanning holiday using a hire caravan, it'll be a more enjoyable trip if you can feel safe on the road with a couple of tonnes or more of living space behind you.

Watch caravan expert, Mike Sandilands from Driver Risk Management, as he shares how to set up and use an electric brake controller for towing.

What is a brake controller?

Because caravans and trailers can be large, heavy and cumbersome, most of them are fitted with their own brakes. However, because those brakes can't be controlled by the brake pedal in your tow vehicle, they need a method of activation so that the trailer slows down when the vehicle does without overloading the vehicle brakes.

Most caravans are fitted with electronic brakes-brakes that are activated by an electrical signal. Less commonly, caravans are fitted with override brakes, which are activated by a slide-coupling that compresses under deceleration. Unless you have a very old caravan, it's highly likely yours has electric brakes.

Brake controllers, therefore, are simply small computers that tell the caravan brakes when to apply braking force and how much. Almost all electronic brake controllers are activated by your vehicle's brake light circuit as well as by a manual override function, which is usually a button or a sliding trigger.

Brake force can be manually adjusted to suit the weight of your van or the driving conditions. However, most modern units also use inertial triggers to progressively apply braking force as needed - i.e., the faster you decelerate, the stronger the braking force applied to the trailer.

Brake controllers come in different shapes and sizes, too. These days, most brake controllers have control boxes that hide behind dash panels with only a dial and button visible on the dash. Older brake controllers were often cassette-shaped boxes fitted below the steering wheel (and ideal for knocking your knee on them). Many popular modern tow vehicles are now offered with optional, factory-fitted brake controllers.

Some brake controllers are even 'wireless'. Rather than having a control box wired into the tow vehicle's brake light circuit, a control box is wired into the trailer's brake light circuit, and this sends and receives a Bluetooth signal to and from a smartphone (or dedicated display) in the vehicle.

The benefit of this is that caravans can be shared across tow vehicles without the need to fit a brake controller to multiple cars. Wireless brake controllers are very popular in peer-to-peer hire fleets.

Do I need a caravan brake controller in Western Australia?

In Western Australia, trailers with a gross trailer mass of less than 750kg don't need their own brakes, so they can safely be towed by any vehicle rated to tow such a trailer, even if it isn't fitted with a brake controller.

A trailer, including a caravan or camper trailer, must have its own brakes if its gross trailer mass (GTM) is over 750kg or if it has two or more axles. If your trailer falls in that category, you probably don't need a brake controller fitted to your vehicle.

In reality, most trailers with an aggregate trailer mass (ATM) of 750kg or less won't have brakes; even though that's not quite the interpretation of the law, but it gives owners some breathing room.

A trailer with a gross trailer mass between 750kg and 2,000kg, or a trailer with two axles up to 2,000kg, must have its own brakes, but they're only required on one axle, even if the trailer has two or more axles. In that weight range, trailers can be fitted with electrically controlled brakes, which require a brake controller to work, or override brakes, which don't require a brake controller to work. Override brakes use the trailer's inertia to compress an override coupling as the tow vehicle slows to apply mechanical or hydraulic brakes.

Trailers with electric brakes need to be towed by a vehicle fitted with an electric brake controller.

Once trailers or caravans exceed 2,000kg, the braking requirements get more specific. According to WA’s Department of Transport, trailers with a GTM heavier than 2,000kg must have brakes that can be controlled from the driver's seat of the tow vehicle. Override brakes are not permitted. That almost exclusively means that brakes must be electronically controlled, and you will need a brake controller fitted to your vehicle. Trailers that are this heavy must also have brakes on all wheels.

To simplify it all, you can answer these questions.

Does my trailer have two axles? If yes, it needs brakes, and you need a brake controller if the brakes are electrically controlled. Does my trailer have a GTM over 2,000kg? You need a brake controller.

It's also important to know that your stopping distance will be longer with a caravan or trailer in tow, even with a brake controller. With a 2,500kg trailer on the back, a typical SUV may take an extra 10 metres to stop from 60km/h, even with trailer brakes.

How do I set up my brake controller?

Although many modern brake controllers are quite intuitive, they still need to be properly set up for your vehicle and caravan and then checked each time you tow. Fortunately, you can usually do all that in the safety of your driveway or a quiet street.

Many new inertially-controlled brake controllers will need to be calibrated and will have specific instructions in the user manual, but usually, it just involves driving slowly on a straight, flat road for a few hundred metres so the unit can understand which way is forwards compared to how it's been installed.

Older cassette-shaped brake controllers could usually only be fitted with the controls accessible to the driver, but could be angled up or down, depending on how they fit into the vehicle. They often have a small wheel that you can turn to tell it how far it's been angled up or down so it can modulate brake force effectively.

Once calibration is done, it's unlikely you'll ever need to do it again unless you move your brake controller or adjust how it's mounted to your vehicle.

Once your brake controller is calibrated, you'll then need to adjust the gain, which is essentially the maximum braking force the controller will apply to the brakes. Usually, this involves spinning a dial or pressing plus and minus buttons to suit.

What you are hoping for, though, is that when you brake the vehicle, the trailer brakes at the same rate. You can usually feel the difference. If the trailer feels like it's pulling on the vehicle under brakes, you drop the gain slightly. If the trailer is pushing on the vehicle under brakes, you increase the gain slightly until it's more balanced.

Depending on the conditions, you may need to make minor adjustments if you notice it's not quite right. You may also need to make adjustments if you're driving off-road or on gravel, as the trailer could lock up more easily if there is less friction for the tyres to fight against.

Although modern brake controllers are usually quite consistent, it would be wrong to assume that one setting is the setting for life.

Using brake controllers in an emergency

The reason caravan brakes need to be controlled by the driver on heavier trailers is so that trailer brakes can be activated in an emergency, particularly in a trailer sway situation.

Trailer sway is one of the scariest things about towing large trailers. It is induced by a lot of different factors, particularly cross winds, driving down hills or being buffeted by larger vehicles, and is exacerbated by incorrect loading. However, caravan sway is essentially just a trailer travelling faster than the tow vehicle. The easiest way to stop it is by slowing down the trailer.

Because all brake controllers have a brake override function, which is a button or slide you press to activate the brakes, you can apply them only on your trailer and slow it down.

You should familiarise yourself with the location of your brake override button and practice being able to press it without looking at it.

Reach down for it at traffic lights, while cruising the highway or at other convenient times to build muscle memory of where it is. That way, when you do need to press it in an emergency, you won't have to take your eyes off the road to do it, and you can mitigate a sway situation before it gets out of hand.