Example - to calculate the maximum 5^th wheeler Tare Mass a 6 cylinder, 1 tonne Falcon ute can tow:

  Kerb Mass of Falcon Ute 1545kg (auto +22kg, tray +115kg, hitch +30kg )   -1722kg

    Gross Capacity                                                                                                        3163kg

  Occupants (2 people)                                                                                160kg

  Luggage, bedding etc                                                                                100kg

  Food, drink etc                                                                                           50kg

  Accessories                                                                                               40kg

  Water (fresh & grey water)                                                                         130kg

    Estimated Combination Payload                                                                             -  480kg

                       Calculated Maximum fifth wheel Tare Mass                                                   2683kg

The combined weight of the fully laden tow vehicle & fully laden 5^th wheeler must not exceed the tow vehicle’s Gross Combination Mass (GCM). Do not calculate the GCM, check the vehicles handbook, for example, the Holden Rodeo TF has a low GCM in relation to its towing capacity and GVM. The GCM stated in its handbook is 700kg less than the calculated GCM.

The tow vehicle’s Kerb Mass should include all accessories and a full tank of fuel. Some manufacturers only include 15L of fuel; Commodore & Falcon kerb weight’s includes a full tank of fuel. Don‘t go by the tare on the rego label – it doesn’t include accesories such as bulbar, tray etc.

20% of the fifth wheel weight should be transferred to the tow vehicle (ball weight) and should not exceed your tow vehicle's rear axle rating.  The hitch we use is a 76mm ball rated at 9000kg which is Australian Design Rule approved, it takes up minimal space on the ute and can be unscrewed if needed. The ball is ideally mounted over the rear axle with 1.2m clearance in front of it; this allows the 5^th wheeler to be manoeuvred at 90 degrees to the tow vehicle.

Some vehicles have a reduce speed limit when towing – consult the vehicle’s handbook.

Maximum dimensions of 5^th wheeler including, accessories (awning, lights, air conditioner etc): width 2.5m (8’2”) height 4.3m (14’1’). If these are exceeded you need a flashing amber light on your cab and an ‘oversize’ placard on your caravan / trailer / fifth wheel.

Kerb Mass = Weight of unladen tow vehicle with accessories fitted and full tank of fuel.

Gross Capacity = Tow vehicle’s carrying capacity.

Combination Payload = Actual weight of luggage, water, food, goods, occupants etc. in fifth wheel & tow vehicle.

Gross Vehicle Mass (GVM) = Maximum allowable tow vehicle weight fully laden.

Gross Combination Mass (GGM) = Maximum allowable combined weight of tow vehicle, fifth wheel and payload.

Aggregate Trailer Mass (ATM) = Maximum allowable fifth wheel weight, fully laden, unhitched.

Gross Trailer Mass (GTM) = Maximum allowable fifth wheel weight, fully laden, hitched. (Not including ball weight).

Ball Weight = Weight the fifth wheel transfers to tow vehicle.