BEFORE we delve into the wonderful world of vehicle loading and how it affects legalities and a vehicle’s handling, it’s useful to understand the terms commonly used.
This is the vehicle’s weight with fluids, usually with only 10 litres of fuel in the tank.
The weight of a rig when it’s ready to drive with full tank/s, an average driver of 68kg (they don’t frequent my souvlaki shop!) and 7kg of luggage. However, tare and kerb weight definitions differ from manufacturer to manufacturer.
Gross Vehicle Mass is the maximum allowable vehicle weight, including all occupants, accessories and luggage.
Gross Combination Mass is the total combined weight of your accessorised, fully loaded vehicle and anything you’re towing.
In addition to GVM, vehicles also have a maximum allowable load on both the front and rear axles.
Aggregate Trailer Mass is the maximum allowable weight of the trailer you’re towing, as designated by the manufacturer.
Tow Ball Mass is the weight on the tow ball imposed by the trailer, usually around 10 per cent of the ATM. For a trailer weighing 3500kg, you’ll have a TBM of around 350kg.
CENTRE OF GRAVITY:
An imaginary point in the vehicle where you could theoretically balance the whole car on one (very strong) finger.
MOMENT OF INERTIA:
When you’re turning around an axis, the further the weight is from the axis of rotation the harder it will be to start and stop.
TYRE SLIP ANGLE:
When turning, there is a difference in angle between where the wheel is pointing and where the vehicle is tracking, due to the flexibility of the tyre.
TYRE LOAD SENSITIVITY:
Conventional pneumatic tyres don’t behave as your high school physics class might suggest. As the load increases, the co-efficient of friction decreases. The peak lateral (cornering) force increases as the vertical load on the tyre increases, but at a diminishing rate.