There are major risks involved in towing a caravan or camper trailer if an under-sized towing vehicle is used. These risks are compounded when the caravan is over weight. South Australian Police from the SA Road Safety Centre say they believe many caravans are overweight.
The Kerb Weight of the potential tow tug is front and centre as a key step towards towing safety.
Towing regulations throughout Australia accept the vehicle makers numbers about what a vehicle can tow. If these numbers are exceeded the law, warranty and insurance will be offended.
The Kerb Weight of the towing vehicle is the unladen weight. It includes all added extras as well as full tank of fuel. Also add, driver, passengers and hand luggage. It is a weight which must be double checked police say as most motor vehicle are personalised with added extras which add weight to the vehicle. Tow Ball Mass can vary.
Some makers include it as part of the load carrying capacity, of their vehicle some do not. Ask the vehicle maker before purchasing a tow vehicle. Ask the vehicle maker whether their vehicle is designed to be strong enough to cope with the stress of towing on the vehicle's structure.
1.Gross Vehicle Mass (GVM). Gross Vehicle Mass is the maximum weight permitted for the motor vehicle as nominated by the manufacturer.
2. Kerb Weight of the tow vehicle.
3. Subtract the Kerb Weight from the Gross Vehicle Mass (GVM) and the result is the tow vehicle's current payload capacity.
4. Ball Weight. The Ball Weight (Rated) is a given weight by the caravan, motor vehicle or tow bar manufacturer. The RACQ says - All tow bars made after July 1, 1988, and many made before this date, will have a plate attached that lists the maximum towing weight, the maximum ball load and the make and model of vehicle the bar was designed for.
The vehicle’s specifications will always be the maximum the vehicle can legally tow, even if the tow bar is rated for a higher load. But if any of the tow bar specifications are lower than those given for the vehicle, the tow bar’s specification will override the vehicle’s specifications.
Editors Note: The actual (operational) Tow Ball Mass or Ball Weight is the mass exerted onto the towing vehicle through the towing hitch when the caravan or trailer is laden. Actual Operational Tow Ball Mass is real world towing.
5. The legal towing capability of a motor vehicle is nominated by the manufacturer. In essence never have more than the Ball Weight as stated in the Vehicle's Owners Manual on the Tow Ball.
6.Aggregate Trailer Mass (ATM). ATM is the fully loaded weight of a caravan or trailer when not connected to the tow vehicle.
7. Rated Tare. Rated Tare is the unladen weight of the caravan or trailer when not connected to the tow vehicle.
8. Subtract the Rated Tare from the ATM and the result is the most optimistic caravan or trailers rated payload capability.
The actual Operational situation with the caravan loaded will reduce that payload capability. For example rated payload for the caravan may be 500kg, but Operational payload for the caravan may be 300kg.
Safety must always come first. The Operational weight of the caravan is the figure to work to.
9. Gross Trailer Mass. (GTM) is the weight of the caravan or tailer transmitted through the caravan or trailers axle/axles to the ground when connected to the tow vehicle. This must exceed the (Rated) Gross Trailer Mass.
10. Ball Weight. Ball Weight is generally 10 per cent of the Aggregate Trailer Mass (ATM).
It is this weight which is transferred to the tow vehicle.
11. Gross Combined Mass (GCM) is the maximum loaded masses of the tow vehicle and anything it is towing. This is as determined by the vehicles manufacturer or by the relevant registration authority.
Editor's Notes: Ground clearance must not be less than 100mm (For any point within 1m fore or aft of any axle, when caravan or trailer is loaded to ATM).
Rear overhang: Measured from the rear of the trailer to the centre of the axle group. This must not exceed the lesser of 3.7m OR the length of the front load space. This includes any other attachments on the rear of the trailer, such as bicycles, spare tyres, fuel containers or boxes.)
Two axles less than 1m apart are considered to be a single axle.
Personal judgement within the laws should be used when towing a caravan in Australia. There are variations, check with State and Federal authorities. Take the time to digest Australian State and Territory road rules as well as vehicle, caravan and trailer manufacturers requirements before travelling.
GoSee suggests The Australian Practical Guide to Towing, released by Tow-Ed. www.tow-ed.com.au as a good source of general information.
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