There are six main aspects involved in towing a trailer:

(1) The Towbar  (2) The Ball Mount or Tongue  (3) The Tow Ball  (4) The Coupling  (5) The Trailer Draw Bar or ‘A’ Frame  (6) The Safety Chains


The towbar is the framework attached to the back of the tow vehicle. For safe towing, a properly designed and fitted towbar with an adequate certified weight rating is mandatory.</5>
Further, the load capacity of the towbar and the trailer coupling must be equal to or exceed the loaded mass of the trailer.

Unless a permanent part of the vehicle, it is compulsory for all towbars manufactured after 1 July 1988 to clearly and permanently display the maximum load rated capacity plus the make and model of vehicle for which they are intended, or alternatively, the manufacturer’s name, trade mark and part number.

Check for this information to help you ascertain whether the towbar suits your needs.

Note: Towbars should not protrude dangerously when your trailer is not connected.



The ball mount, also known as the tongue, is the section of the towbar to which the towball is attached. It is usually a flat 75mm wide, 16 to 20mm thick steel bar, which may be either straight or curved to achieve the correct coupling height.

If the ball mount or tongue obscures the number plate it must be removed from the towbar when the trailer is not attached.



Based on Australian Design Rules & Standards, tow balls suitable for ATM weights up to 3500kg:

Must be 50mm in diameter, and stamped on top of ball as a legal requirement.

Must be a one piece element, the shank of which should be 29mm in diameter.

Must be fitted to the vehicle with a locking washer and appropriately sized nut.

Must have the manufacturer’s name or trademark stamped on the flange of the towball.

With the tow vehicle loaded to GVM, the towbar (if fitted with a 50m towball) on the towing vehicle must be capable of being mounted (adjusted) to any one height within the range of 350mm to 460mm (from the ground to the centre of the towball).




The coupling body is the section that is attached to the ‘A’ frame of the trailer. It forms a socket for
the tow ball and provides the necessary pivot point between the trailer and the towing vehicle. Coupling bodies commonly in use can range in capacity from
750kgs to 3,500kgs. They must be marked with their capacity, as well as the manufacturer’s name and the size of the tow ball for which they are suitable. It is important to ensure that the coupling body’s capacity exceeds or is at least equal to the fully
laden weight of the trailer. Regardless of coupling capacity, the 50mm ball must still comply with the capacities outlined under the heading tow ball.


Off-Road couplings are designed for use where high degrees of articulation are required. Some use a separate pin to connect, whilst others use a built-in locking mechanism. Many have polyurethane components to absorb shocks.

All of these couplings are required to incorporate a positive locking mechanism plus a separate means of retaining this mechanism in the locked position. This locking must be readily verifiable by visual examination.

Both parts of the coupling must be marked with the Manufacturer’s name or trademark, the words “use with model (identified model)” and the maximum allowable trailer ATM i.e. 3500kg at which the coupling is rated.

The coupling must be strong enough to take the weight of a fully loaded trailer.