Your vehicle’s towing capacity is a factor of its engine size, brakes, weight, transmission, tyres, chassis, suspension etc. After taking these variables into account, the vehicle’s manufacturer establishes a recommended towing capacity, which must be adhered to. This is known as Gross Combined Mass (GCM) being the maximum combined weight of the motorhome or tow vehicle plus the weight of the towed trailer, car or caravan and cannot be exceeded. The GCM is displayed on the tow vehicles compliance plate.
In addition, the maximum load rating specified or recommended by the caravan or trailer manufacture also cannot be exceeded. Caravans have a manufacturer’s plate attached which displays the ATM, which is its maximum allowable weight and also displays the axle, tow ball and load carrying capacities plus the tare weight.
Throughout Australia, the allowable maximum mass for the trailer/caravan is either the capacity of the tow vehicle’s towing attachment or the towing limit specified by the vehicle manufacturer for the towing vehicle, whichever is the least.
With regards to the construction of the tow vehicle, its body must be sturdy enough to attach a tow bar of suitable capacity for the trailer/caravan/tow vehicle you intend to tow. Some vehicles may require structural reinforcement and/or use special suspension and load distribution devices before they can satisfactorily tow heavier trailers, tow vehicles or caravans. You may also need to make other modifications to your vehicle, which could include:
- Fitting 12 volt electrical connection: a seven/twelve pin electrical connector (which is compulsory in Australia) provides the electrical power to operate the trailer lights as well as electric brakes.
- Fitting a suitable brake controller and connection: all trailers or caravans of 750kgs GTM or more must be fitted with brakes. Electric brakes are the most commonly used and require a brake controller, with appropriate connections to the trailer or caravan, to be fitted in the tow vehicle;
- Extra mirrors may need to be added to the tow vehicle when towing large trailers or caravans. It is a legal requirement that the driver has a clear and unobstructed view of the road at all times;
- Remember that towing a trailer, tow vehicle or caravan will decrease your vehicle’s acceleration and braking performance. It will also reduce vehicle control and manoeuvrability, while increasing fuel consumption.
Apart from adding to the driver’s legal responsibilities, towing requires a greater degree of knowledge and skill than normal driving.
When towing, you should:
- Allow for the extra length and width of the trailer or caravan when entering traffic
- Apply the accelerator, brakes and steering smoothly and gently to avoid sway, especially in wet or slippery conditions
- Avoid applying the towing vehicle’s brakes if the trailer or caravan begins to sway or snake. Continue at a steady speed or accelerate slightly until the sway stops
- Maintain a space of at least 60 metres between you and the vehicle in front to allow for a longer stopping distance;
- Engage a lower gear in both manual and automatic vehicles to increase vehicle control and reduce brake strain when travelling downhill
- Allow more time and a greater distance in which to overtake. When towing, your vehicle’s capacity to accelerate is reduced
- Where areas are provided, pull off the road to allow traffic building up behind you to overtake
- Be aware that towing is more stressful than normal driving and is more likely to cause fatigue. Therefore, more rest stops should be planned.
- Ensure you load your tow vehicle, trailer or caravan correctly.
It is important not to overload the caravan or to exceed the maximum load specified or recommended by the caravan or trailer manufacturer. In addition, the tyre or coupling capacities should also not be exceeded.
Loads have to be distributed correctly throughout the caravan or trailer and ensure heavy items are placed above its axles. Incorrect loading with weight too far forward or too far to the rear can cause light steering on the tow vehicle and vehicle sway.
For safety and ease of towing, the ball mass (the mass of the caravan carried by the tow ball of the towing vehicle) should be about 10% of the total laden caravan weight and should not exceed the tow ball weight rating of the tow bar.
Weight load distribution
See image opposite