Understanding towbars

By: Philip Lord

When it comes to towbars, there are a few rules of the road.

Understanding towbars
Like just about anything to do with road vehicles, there are lots of rules governing towbars

When towing, we often think about the many requirements for vehicle and van, but forget about the vital link between them – the towbar.

A towbar has, arguably, the toughest job of all in a towing rig. The loads imposed on it can be very high. And, aside from the job of keeping the caravan attached, the towbar has even more load to deal with when you add a load-levelling device.


There are two typical designs of light-duty towbars for cars: one that is a fixed hitch type (‘fixed’ in that the tongue is permanently bolted or welded to the towbar frame and not easily removed) and usually meant for lighter-duty towing of up to around 1200kg; and the removable tongue style.

There is another, less common, version popular in Europe called a ‘swan neck’ towbar. The swan neck towbar has the towbar body bolted to the vehicle as per any other passenger vehicle towbar, but the tongue is a swan neck shape with the towball integral to it. This tongue is either bolted to the towbar body or has a quick-release connection so the tongue can be removed and stored away when not towing. This towbar design can have compliance problems in Australia. We’ll cover that further on, though.

Another light-duty design is the removable tongue to hitch receiver, with usually a 40x40mm solid-mount tongue. This is secured in the hitch receiver with a pin and circlip. Some Subaru and Honda models, among others, use this design.

The most common heavy-duty style of towbar is the 50x50mm hitch receiver with hollow tongue held in place in the hitch receiver with a pin and circlip. You’ll find this design on most tow tugs and, typically, towing capacity can range anywhere from a 1600kg to 3500kg.

There are exceptions to the rule, such as Land Rover’s towball mount on the Discovery 3 and Range Rover Sport. This is similar to the European swan neck design in concept, except that, instead of a one-piece tubular steel neck and ball assembly, the Land Rover design uses a detachable 50mm receiver. To this, a 50mm tongue is secured with a pin.


Like just about anything to do with road vehicles, there are lots of rules governing towbars. Australian Design Rule (ADR) 62 became effective in July 1991 and is a combination of Australian Standards developed over the years, which refines the requirements and testing of towing equipment such as towbars.

Just to make things more complicated, there are two revisions of this legislation: ADR 62/01 (2006) and ADR 62/02 (2009). Vehicles built before the updated ADR came into being can comply with the earlier ADR. Here, we’ll focus on ADR 62/02 – the current legislation.

There is so much confusion about this legislation and to say it is misleading is an understatement. Here, we will try to unravel some of it. Part of the problem lies in the fact that ADR 62/02 states that the towbar and attachment points need to comply with AS 4177.1-2004. But ADR 62/02 does not state what those requirements are – you have to buy a copy of the Australian Standard to find out.

All new towbars have to comply with the strength, function and identification requirements of ADR 62. Quite a bit of testing is required for these towbars. The ADR lists static and dynamic forces that the towbar must be able to withstand ‘when these forces are applied separately at the intended "coupling" centreline, without incurring any residual deformation that would interfere or degrade the function of the assembly or any breaks, cracks or separation of components’.

The towbar must sit at a certain height, too. The height to the centre of the ball, determined when laden, must be between 350mm and 460mm.

The ADR also requires the towbar be marked with several forms of identification. The towbar must clearly and permanently display the towbar manufacturer’s name or trademark, except where it is an integral part of the vehicle; the make and model shown on the compliance plate fitted to the vehicle for which it is designed or the manufacturer’s part number; and its maximum rated capacity expressed in kilograms in numerals, not less than 2.5mm high, for both maximum-rated towing capacity and maximum-rated towball download. The maximum-rated capacity must be the Aggregate Trailer Mass for which the towbar is designed and must not exceed the motor vehicle manufacturer’s recommendation. The words ‘for trailer towing only’ must appear on the plate.


The towbar, according to AS 4177.1-2004, has to have two safety chain attachments capable of withstanding the loads imposed. These can be on the towing tongue if the tongue is attached with two threaded fasteners or if it is attached with a self-locking connector. So, in other words, the light-duty flat tongue style or Euro swan neck style towbars mentioned above can have safety chain points that are not on the towbar body, but there must be two.

Confusion exists here because ADR 62/02 clause 13.4.3 states, ‘Towbar safety chain attachments must be fixed to a part of the "towbar" which is permanently attached to the vehicle’. You have to read AS 4177.1-2004 to see what ‘permanently’ really means.

The Australian Standard for towballs is a 50mm diameter and the rating of the towball has to be stamped on the ball. Towballs for heavy-duty applications usually have a 3.5t rating, but just confirm that the rating on the ball is higher than the weight you plan to tow, and that a locking washer is fitted to secure the nut.

Though it is rare with new towbar fitments these days, if the tongue obscures the number plate it must be removed when driving without a trailer attached.

There is not much involved in looking after a towbar. The towball must be bolted on tight, and the tongue also if it’s a bolt-on type. You really need to seek out the specifications of your specific towbar, but the main securing bolts can require upwards of 100Nm of tightening torque and the towball more than 130Nm.

Check the hitch locking pin and circlip are fitted properly if using a hitch receiver type of towbar. With a new vehicle and/or towbar, it wouldn’t hurt to occasionally inspect the towball mounting points for fatigue cracks and also check the wiring plug for obvious signs of deterioration, such as loose or corroded wires, while you are there.

The full feature appeared in Caravan World #537 May 2015. Subscribe today for the latest caravan reviews and news every month!