What is ball weight on a caravan?
The share of the van's weight that presses down on your tow ball.
Ball weight is the downward force the van's coupling puts on your tow ball. Road authority guides put it at about 5 to 10 per cent (NSW) or 8 to 10 per cent of ATM (WA). A maker's figure is often for the empty van. It is carried by the car, so it comes out of the car's payload. Check it against the car's towball limit, the towbar's label and the towball's stamp. The lowest applies. Too little of it can make the van sway. Too much can overload the car's rear axle.
Also called tow ball mass, tow ball download, TBM.
- Commonly - about 5 to 10 per cent (NSW) or 8 to 10 per cent of ATM (WA)
- Carried by - the car, so it counts against the car's GVM (Gross Vehicle Mass)
- Limited by - the car, the towbar and the tow ball, each with its own rating
What ball weight does
A caravan rests on its axles with part of its weight forward of them.
That forward share presses down on the tow ball, and it is the ball weight.
Some ball weight keeps the van steady behind the car.
Too little and the van can sway at speed.
Too much can overload the car's rear axle and the towbar.
Ball weight across the caravans we list
Among the caravan ranges we list, the middle published ball weight is about 190kg.
Half are above that figure and half below it.
Your own figure moves with how you pack, so weigh it loaded.
Who carries the ball weight
The car carries the ball weight, so it counts against the car's GVM.
Hitch a van with, say, 250kg on the ball and the car has 250kg less for people and gear.
Three ratings on the same number
Several ratings apply to the same ball weight.
The lowest of them is your limit.
The van's coupling is rated for the van's ATM instead: 750, 2,000 or 3,500kg.
- The car - its maximum ball weight is in the owner's manual
- The towbar - its rating is on the towbar's own plaque
- The tow ball - the ball or hitch head carries a rating of its own
How to measure ball weight
A tow ball scale under the coupling gives a direct reading.
Set the coupling at the height it sits when hitched to the loaded car.
A weighbridge can work it out in two weighs.
Release a weight-distribution hitch first.
Weigh the van hitched, with only its wheels on the scale.
Then unhitch it and weigh it again with the jockey wheel on the scale too.
The difference between the two is the ball weight.
How little margin a ball limit can leave
These figures are made up and rounded to keep the sums simple.
Take a van loaded to a 2,800kg ATM (Aggregate Trailer Mass).
At 10 per cent, its ball weight is about 280kg.
If the car allows 300kg on the ball, that leaves 20kg of margin.
Moving one heavy box forward of the axles can use it up.
Common mistakes with ball weight
- Trusting a published figure - it is often for the empty van, and packing moves it. Measure it loaded
- Forgetting the car's payload - ball weight comes out of what the car can carry
- Loading the rear - heavy gear behind the axles lightens the ball and can cause sway