How much weight can your car safely tow?
One of the drawcards of owning a Caravelair is that they are lightweight and easy to tow. Caravelair have a base weight starting from just 830kgs, which means that they can be towed by almost every car on the road.
In saying that, there is some important information you need to be informed about before you start towing a caravan, which is not only practical but is also required under law so that you are kept safe on the roads.
Before we continue, here are some definitions you might find helpful:
- Kerb Mass / Tare Mass – the unladen mass of the vehicle
- Gross Vehicle Mass (GVM) – the total mass of the vehicle including its load
- Gross Combination Mass (GCM) – the total mass of a loaded vehicle and its loaded trailer
- Gross Trailer Mass (GTM) – the mass supported by the axle/s or wheels of a loaded trailer
- Aggregate Trailer Mass (ATM) – the total legal loaded mass of a trailer including the tow ball download
- Tow Ball Mass / Download – the mass transferred by a trailer onto the rear of a tow vehicle
What are the National Towing Regulations?
In December 1998, an agreement was reached by all State Ministers of Transport to implement National Towing Regulations.
In essence, the National rules state that a motor vehicle with a GVM not exceeding 4.5 tonnes, can tow a loaded trailer with an ATM up to:
The lessor of:
- The tow vehicle’s towbar rating (including the tow ball mass / download rating). This information should be shown on a plate attached to the tow bar; OR
- The tow vehicle manufacturer’s recommended maximum trailer towing mass (including the tow ball mass / download rating).
Where the tow vehicle manufacturer does not specify towing mass data, the vehicle may legally tow:
- A loaded trailer with brakes – up to 1.5 times the unladen mass of the vehicle; OR
- A loaded trailer without brakes – not exceeding the unladen mass of the vehicle.
It should be noted, however, that the above will rarely apply as apart from using a truck, just about every vehicle that is likely to be used for towing a caravan, dog trailer, horse float or similar, has a manufacturer’s towing recommendation.
If the above sounds confusing, to put it simply, the most you can tow is the amount specified by the vehicle manufacturer or the capacity of the towbar – WHICHEVER IS LEAST.
It is also important to mention that the maximum GTM of an unbraked trailer must not exceed 750kgs.
While this all may seem difficult to understand and take some work to figure out, it is important for your safety as well as to not void the warranty or your insurance.
But don’t worry, some of the equations have been done for you. Your tare, ATM, TBM, and GTM will be stamped on the VIN (vehicle identification number) plate of your vehicle. A lot of the other numbers can be found in your owner’s manual and documentation for both your vehicle and your caravan, which should also include the manufacturer’s towing recommendations.
You can also use a public weighbridge to figure out the exact weight of your vehicle when you are all packed up, to check your caravan weight, and to find out the weight of both together.
Owners of 4WDs and light commercial vehicles should also be careful that they do not exceed the GCM of the vehicle. The GCM refers to the maximum vehicle plus its load, including a trailer, is permitted to weigh. For example, it is possible that when a motor vehicle is loaded with five adults, their luggage and camping gear, that the maximum allowable trailer mass has to be reduced so as to not exceed the GCM.
To recap, here are the sums you are going to need to know:
- ATM = caravan tare mass + caravan max payload
- GVM = vehicle tare mass + maximum payload
- Maximum payload = ATM – tare mass – tow ball mass
- GTM = ATM – tow ball mass
- GCM = GTM + GVM
- TBD / GTM x 100 = % of GTM
Load Distribution / Levelling Devices
Another item to consider is that weight should be distributed as evenly as possible between the front and rear axles of your vehicle.
When the weight isn’t distributed properly across the car, it can cause unnerving trailer sway, reduced steering and braking responsiveness, less traction and misaligned head lamps. Over time, you may also notice a reduction in fuel economy and an increase in tyre wear.
When using a load distribution/levelling device, this will assist the load in being evenly distributed through the vehicle’s chassis to all four wheels. It is important that the capacity of the distribution/levelling device is correctly chosen and that the vehicle manufacturer’s recommendations are always followed.