In Australia it is compulsory for all trailers over 750kg ATM to have brakes on at least one axle. Over 2000kg brakes need to be on all axles.
For trailers under 4.5T there is no performance requirement for brakes, they only need to be 'efficient'. Vehicle Components chooses to use European Legislation as a guide in the performance specification of brakes.
Drum brakes come in a variety of sizes and can be actuated hydraulically, electrically or mechanically. Disc brakes can be hydraulic or mechanical.
Overun brakes are permitted up to 2000kg GTM providing the trailer weighs less than the unladen weight of the towing vehicle. These operate mechanically directly through an overun coupling or via a hydraulic cylinder attached to the coupling.
Over 2000kg GTM the brakes must apply for 15 minutes if the trailer becomes detached from the towing vehicle. The easiest way to meet this requirement is to use electric brakes. Electric brakes can be actuated via a controller on the drawbar of the trailer (not recommended) or by an in-cab controller which can be adjusted by the driver to suit loading and road conditions.
Electric marinised brakes are available for boat and off-road applications.
More complex systems can use electric/hydraulic, vacuum/hydraulic, air/hydraulic or air/mechanical.
The efficiency of the braking system will depend on the rolling radius of the tyre. The bigger the tyre the less effective the brakes. The following chart shows the maximum axle load in Tonnes to achieve a 0.5G deceleration.
TYPE
TYRE DIA 630MM
TYRE DIA 710MM
TYRE DIA 790MM
9in DRUM Mech/Hydr
1.3
1.15
1.0
10in DRUM Elec/Hydr
1.8
1.6
1.4
11in DRUM Mech/Hydr
-
2.2
1.9
12in DRUM Elec/Hydr
-
-
2.5
10in DISC Hydr
1.8
1.6
1.4
10in DISC Mech
1.3
1.15
1.4
12in DISC Hydr
-
2.2
1.9
12in DISC Mech
-
1.6
1.4
As legislation may change from time to time and between states it is important to confirm with your licensing authority the current requirements.
Brake Control
