Trailer Brakes

Posted on 04/10/2018

Towing trailers for most people is a sign you're on holidays onto a destination to a fun filled adventure or moving vital equipment to a job site. So ensuring you're towing safely is important. One of these safety features are the brakes on your trailer or caravan. To understand what you require for your trailer, first we need to understand some technical weight jargon.

What does TARE, ATM and GTM mean?

TARE mass is the weight of your trailer (or caravan) stock standard, this means no water, no gas tanks, no additional equipment that the trailer (or caravan) didn't come with when the keys were handed over to you (or the original owner).

The Aggregate Trailer Mass (ATM) is the weight of your trailer or caravan plus its maximum permitted payload (equipment, luggage, household items for camping, gas tanks, water tanks, etc) in an UNHITCHED setting. The ATM is calculated based on the lowest value of things like tyres, axle capactity, etc.

The Gross Trailer Mass (GTM) is the weigh of a trailer or caravan fully loaded to its maximum payload in a HITCHED setting (attached to a vehicle) and therefore sitting on its axles.

Braking Requirements

Now with that over, lets see what you need. In order to understand what you need to correctly brake your trailer you must figure out what your GTM is (this is located on an ID plate riveted to your draw bar. Again, this is your maximum allowable trailer weight. If your trailer weighs less that 750KG including its payload then you do NOT need to have your trailer braked. However if you are between 750KG at 2000KG then you require at least an Override braking system shown below:

However most trailers and caravans over 750kg use electric brakes for their towing needs, electric brakes also become mandatory OVER 2000kgs. Tow vehicle must be fitted with a controlling module to control the electrical signal required to operate the trailers electric brakes.

Controlling units for electric brakes

Brands commonly used are REDARC, Tekonsha and Hayman Reese. REDARC TowPro is by far the most popular and is shown below:

And when fitted to a vehicle, all you see is a controller knob, as shown below:

These trailer braking controllers utilise the vehicles power supplies and brake light signals, combined with internal G-Force sensors to figure out how much power to put to the trailers brakes. They also have an override function that should your trailer start to sway or become uncontrollable, you can manually push a button or slide a level in order to manually activate the trailers brakes and not the vehicles so as to slow the trailer down resulting in the trailer and vehicle "stretching" and bringing the trailer back under control.

Break Away Systems

For all caravans over 2000kg GTM all states require a trailer break-away braking system be installed. This is a unit that if the trailer ever comes off the towing vehicle activates the trailers electric brakes via a small backup battery mounted in the caravan. The most common unit fitted is the BreakSafe 6000:

NSW law also requires a unit fitted to the vehicle which monitors this battery when connected to the tow vehicle. These must visually or audibly notify you if the battery is failing in the Breaksafe unit. The monitoring unit usually looks like this: