Technical Definitions

Light trailers are vehicles without motive power (i.e. they do not have the ability to propel themselves) and have a maximum gross vehicle mass (GVM) or gross laden weight (GLW) of 3500kg or less. Light trailers includes class TA trailers (GVM < 750kg) and class TB (750kg ≤ GVM < 3500kg).

Trailer service brakes engage, and often regulate, the trailer’s brake effort in conjunction with, or in relation to, the towing vehicle’s brake application, and assists the towing vehicle to slow down and stop.

A trailer parking brake holds an already immobile trailer and is capable of remaining applied for an indefinite period without further attention. Unlike service brakes, parking brakes are not used in conjunction with the towing vehicle to slow down and stop.

Trailer mounted disc brakes consist of an exposed, disc-shaped rotor and an edge mounted caliper. The caliper compresses brake pads against the rotor, which is, in turn, reduces the wheel’s rotational speed. It offers a simplistic, low maintenance trailer braking option that is mechanically or hydraulically operated. They are suitable for all braking applications and can be submerged in the water safely.

Drum brakes house its major components inside a large metal drum that rotates along with the wheel. By means of a hydraulic or electrical mechanism, brake pads are pressed outwards against the inside of the drum, reducing rotational speed. This brake type offers an economical and effective braking solution, whilst also providing smooth, damped braking that is ideal for fragile goods or animal transportation.

Indirect braking systems, or indirect service brakes, operate without direct input from the driver of the tow vehicle. They can be either inertia-activated or electric (brake-light activated), and both disc brakes and drum brakes can be used in this system. If electrically activated brakes are used, a trailer-mounted brake controller is needed to adjust the braking force. Indirect braking systems are the most commonly used braking systems on trailers rated GLW (Gross Laden Weight) ≤ 2500kg, and cannot by law be used on trailers rated between 2501kg ≤ GLW ≤ 3500kg.

Inertia-activated systems:

Electric (brake-light activated) systems:

Direct braking systems, or direct service brakes, operate as a direct result of braking input from the driver of the tow vehicle. They are load–adjustable and incorporate an emergency over-ride function mounted near the driver’s seat, which operates the trailer brakes independently of the tow vehicle. Brake types used for direct systems are hydraulic disc and electric drum brakes. Trailers rated between 2501kg ≤ GLW (Gross Laden Weight) ≤ 3500kg are required by law to employ direct braking systems.

Electric-hydraulic systems:

Electric systems:

A break-away brake system is a service or parking brake fitted to a trailer that ensures, under all conditions of use, that if the trailer is unintentionally disconnected from its towing vehicle, the brakes will immediately engage in order to bring the trailer to a halt. The action time of the break-away brake must be a minimum of 15 minutes.

A trailer that utilizes two or more axles, mounted independently of each other, cannot equally distribute the trailer weight between the axles when traversing uneven terrain, or when the towing vehicle’s tow ball and trailer coupling are not at the same height. Such a suspension system is classed as a non-equalizing suspension system. Although an economical option, periodic point loading can cause bearing and suspension failure, and result in poor towing characteristics.

Equalizing suspension systems consist of multiple axles with a rocker arm between each axle. This enables the axles to have greater, independent vertical travel whilst maintaining full weight carrying capacity at any point and effectively distributes the weight between all axles. Axle overloading is mitigated, prolonging axle, hub and bearing service life, and towing characteristics are improved.