Certain equipment is mandatory for towing any trailer

This includes obvious things like tow bars and trailer wiring connectors. However, particularly where the trailer mass is approaching the upper limit of the vehicle’s specifications, its manufacturer may mandate certain additional equipment. Load levelling devices, high capacity tow bars, heavy-duty rear suspension, additional oil coolers and brake controllers are examples. Where specified, this equipment must be fitted.

About towbars

Just because the car you bought came with a towbar, don’t automatically assume that it’s suitable for a caravan or other heavy trailer. Many towbars are only intended to tow light trailers and will be totally unsuitable, illegal and potentially unsafe for heavy use.  Use of an inadequately rated towbar could result in loss of the trailer or structural damage to the towbar and / or vehicle. 

Towbars are available from a number of sources, but most commonly they are purchased from a specialist towbar manufacturer or as original equipment from the vehicle manufacturer’s spare parts and accessories outlet.

When buying a towbar there may appear to be a price benefit in buying non-genuine, but keep in mind that the vehicle manufacturer’s towing package is often more than just a towbar. Such packages can often include things like heavy-duty suspension and additional transmission oil coolers, all of which are designed to maximise safety and vehicle durability.

Another point often overlooked is the height of the vehicle’s tow bar in relation to the trailer’s draw bar. For best results the trailer should be slightly “nose down”. If it tows “nose up", it may be unstable. Usually problems such as this can be corrected but it is work best left to a specialist in the field.

If the tow bar tongue or ball obscures the rear number plate, it must be removed from the towbar when not in use.  
For further information about tow bars see Trailer and Tow vehicle specifications.

Load distribution / levelling devices

Load distribution devices are used to return the tow vehicle’s attitude to as near level as possible once the trailer has been connected. This benefits steering control and braking. They are available in a range of sizes and styles to suit the particular application.

However the vehicle and towbar must be strong enough to withstand the increased loads imposed by such systems. If the towbar does not have provision for, or was not originally intended to have a load distribution device fitted, the advice of the towbar manufacturer should be sought before fitting one.

Some vehicle manufacturers specify load-levelling devices as a mandatory part of their towing package, however some specifically advise against their use due to towbar and vehicle design issues. Using a load distribution hitch with a vehicle or towbar not designed for it can cause major structural damage to the vehicle and / or the towbar.

Load distribution systems are not intended to compensate for excessive ball or rear axle loads or to correct poor trailer loading.

Other levelling devices include height adjustable shock absorbers and original equipment self-levelling suspension systems. Before attempting to tow heavy loads with self-levelling suspension systems, or using weight distribution devices with them, the advice of the vehicle’s manufacturer should be sought.

Safety chains 

All States and Territories require light trailers to have safety chains to link the trailer to the tow vehicle. Safety chains must be strong enough to hold the trailer should the trailer coupling accidentally disconnect.  The safety chain/s must have sufficient length to allow the normal articulation of the trailer but be short enough to prevent the drawbar hitting the ground in the event of a disconnection.

Trailers up to 2500 kg ATM are required to have one safety chain while trailers from 2,500kg to 3,500kg must be fitted with two safety chains. 

Trailers with an ATM of greater than 3,500kg must have two safety chains made from T grade chain that meets the requirements of AS 2321 and have a break load limit exceeding the trailer’s ATM. 

Where two safety chains are fitted they should cross diagonally under the drawbar i.e. the right safety chain will connect to the left attaching point on the towbar and the left chain attaches to the right side of the towbar.

Safety chain shackles

It's common practice to use shackles to attach trailer safety chains to vehicle tow bars. Where a shackle is used it must be appropriate for the job.

Queensland's Department of Transport and Main Roads recommends that a shackle used for this purpose:
  • complies with Australian Standard AS 2741-2002 “Shackles” or other equivalent recognised standard; and
  • have a break load limit at least 1.5 times greater than the ATM of the trailer.

AS 2741-2002 compliant shackles will be legibly and permanently marked with the following information:
  • The manufacturer’s name or trademark
  • Quality grade of the shackle, e.g. (‘M’ or ‘4’, ‘S’ or ‘6’)
  • Working Load Limit (WLL) or Rating; and
  • Identification marking in order to correlate shackle to test certificate

However while this is a recommendation, it is not legislation and there are many shackles in use that have an appropriate load rating but don’t comply with the marking requirements listed above.  That aside, the fundamental requirement is that whatever is used to connect the safety chain to the tow vehicle must have adequate strength to retain the trailer in the event of a disconnection (with a margin for dynamic loads, hence the requirement for a factor of 1.5 times the trailer’s ATM).  The recommendation is to use a load rated shackle because that way it’s clear what it’s rated for.  Anything else is a guess. 

Many of the shackles on the market, even some sold by vehicle and tow bar manufacturers, meet the load requirements but aren’t marked (as outlined above) in accordance with the Australian Standard because they don’t have to be. It’s important to note that the Australian Standard referred to relates to lifting equipment, not towing equipment.
 
Our view is that it’s better to have a rated and marked shackle because that way you know exactly what you have and it’s easy to demonstrate that you’ve taken all reasonable steps to ensure it’s appropriate for the job.  If you use something else, in the event of a problem, you may have to show that what you did was acceptable, possibly in court.  

Note the requirement outlined above relates to the shackles Breaking Load Limit. However shackles are marked with their Working Load Limit.  The Breaking Load Limit of a compliant shackle is generally six times its Working Load Limit.  i.e. under these recommendations the shackle is specified on its Breaking Load Limit, not its Working Load Limit.

To determine the correct shackle for a trailer's ATM use this calculation.

Example: For a trailer with an ATM of 2575kg the calculation would be 

(ATM X 1.5) ÷ 6 = required WLL of shackle      (2575 X 1.5) ÷ 6 = 643.75

From the chart provided below the minimum Working Load Limit of a shackle appropriate for this application would be satisfied by an 8mm S or 6, or alternatively a 13mm M or 4.


Diameter (mm) WLL (kg) Quality Grade Marking Diameter(mm) WLL (kg) Quality Grade Marking
6 250 M or 4 16 1500 M or 4
500 S or 6 3200 S or 6
8 750 S or 6 19 2000 M or 4
    4700 S or 6
10 500 M or 4 22 3000 M or 4
1000 S or 6 6500 S or 6
11 1500 S or 6 25 3800 M or 4
    8500 S or 6
13 750 M or 4 29 5000 M or 4
2000 S or 6 9500 S or 6


The following simplified guide, based on Aggregate Trailer Mass, will assist in selecting an appropriate shackle. 

ATM (kg) Shackle pin size Grade markings Alternative
Up to 4500
11mm
‘S’ or ‘6’

Up to 4000
10mm
‘S’ or ‘6’

Up to 3000
8mm
‘S’ or ‘6’
13 mm  ‘M’ or ‘4’
Up to 2000
6mm
‘S’ or ‘6’
10mm   ‘M’ or ‘4’
Up to 1000
6mm
‘M’ or ‘4’


Notes:

  • Specialised shackles of this type are generally not available from hardware stores or similar.  Instead we suggest consulting a caravan or trailer accessory outlet or a supplier of lifting equipment.
  • Both Dee and Bow shackles of the appropriate grade are acceptable. Bow shackles provide for greater angular usage compared to Dee shackles.
  • Stainless steel shackles are unsuitable for safety chain connections due to the material’s generally low resistance to bending stresses.
  • Un-rated shackles must not be used as there is no way of determining their WLL without destructive testing.

Trailer brakes  

  • Trailers up to and including 750kg GTM do not require brakes* 
  • Trailers not over 2,000kg GTM must have brakes that operate on at least one axle 
  • Override brakes are acceptable on trailers up to and including 2,000kg GTM 
  • Trailers over 2,000kg GTM are required to have brakes that apply automatically if the trailer becomes detached from the towing vehicle 
  • Trailers over 2,000kg GTM must have brakes on all wheels 
  • Brakes other than override systems must be able to be operated from the driver’s seat 

* Note that some vehicles have a low un-braked trailer weight limit and will therefore require brakes to be fitted to trailers that have a GTM of less than 750kg.

The cost and complexity of trailer brake systems will vary depending on the application, however where required, most light trailers will have either override or electric brakes
Override brakes are self-contained in the trailer and are self-acting, being activated by the slowing of the towing vehicle. Override brakes cannot be applied independently of the tow vehicle’s brakes. 

Most electric brake systems require the installation of a control unit in the tow vehicle and operate from a signal provided by the tow vehicle’s brake system.  Electric trailer brakes can usually be applied independently of the tow vehicle’s brakes and incorporate a system that allows the trailer braking force to be adjusted from the tow vehicle. 

Brake systems that apply automatically in the event of a trailer disconnection are known generally as Breakaway Systems.  Light trailers that require breakaway systems will often have an electrically operated system that has a storage battery on the trailer to maintain brake operation for the designated period of time. 

Extended towing mirrors 

Extended towing mirrors are required where the vehicle’s existing mirrors cannot provide a clear view past the caravan or trailer. There are a number of variations on the market and you will need to choose the type that best fits your vehicle and needs.

Rear view cameras are now relatively affordable and can be used to provide a view of the blind spot directly behind a caravan.  However it can be difficult to judge distances with them and they are definitely not a substitute for extended mirrors.  Rear view cameras may also be of some benefit when reversing or manoeuvring into parking spaces.

Do not overtake signs

Vehicles, including combinations of tow vehicles and trailers, exceeding 7.5 metres in length may be fitted with “Do not overtake turning vehicle” signs. However if the vehicle exceeds 7.5 metres and needs to straddle a lane when turning at an intersection, these signs become mandatory. These signs are not permitted on vehicles less than 7.5 metres in length.

Upgrades

There’s a plethora of accessories and equipment on the market intended to improve some aspect of a vehicle’s towing performance or behaviour.  Some products may produce genuine benefits in some circumstances, while others may be of questionable value.  And it can be difficult, or in some cases nearly impossible, to readily determine which category some of it fits into.  

Some even constitute major modifications which are intended to make the vehicle do things it was never designed for, or to address some perceived or real operational shortcoming.  

GVM upgrade kits are an example. Such kits are manufactured solely to address issues of limited payload (they cannot increase tow capacity) in a small range of popular vehicles.  
Be aware though that some equipment will require certification and /or approval by the relevant transport authority, some may have insurance implications and will almost certainly impact the vehicle’s warranty cover (where applicable), and potentially its resale value.  

Like a great deal of aftermarket equipment you’re likely to be largely on your own when it comes to determining its value or appropriateness.