Towing can be confusing and not just for beginners. So lets get straight into what the terms mean, how to calculate your own weights and common mistakes when it comes to working out weights.

Definitions

Tare Weight – Tare weight refers to how heavy the camper/caravan is whilst in the yard on display, no water in the tanks, no gas in the bottles. Sometimes referred to as unladen weight.

ATM – Also known as Aggregate Trailer Mass refers to the total weight of the Van at capacity i.e. The maximum legal weight your van can weigh fully loaded.

Ball Weight – Sometimes known as Drawbar weight, Ball Weight is the weight at the hitch. Most vans have a Ball Weight which is measured while the van is empty (tare weight), some vans even provide a maximum ball weight.

GTM – Also known as Gross Trailer Mass. Traditionally the Gross Trailer Mass was the maximum legal weight transferred onto the axles on the caravan/camper. An easy way to visualise this is weight of the caravan at capacity when hitched onto a tow vehicle, the Ball weight is transferred onto the towing vehicle leaving the GTM. Recently the Caravan Industry Association of Australia (CIAA) has updated the definition to be the axle tare weight plus 90% of the payload.

Axle Tare Weight – Using the same example as with GTM, Axle tare weight refers to the weight of a caravan at tare when connected to a tow vehicle i.e. tare weight minus the ball weight

Payload – payload refers to the weight a caravan/camper can carry before reaching ATM.

Laden Ball Mass – Laden ball mass is the empty ball weight plus 10% of the payload.

How to Calculate the weight of your van

Please Note: Best practice for measuring weights of a caravan are to take your van to a weighbridge. To find your nearest weighbridge please visit the National Measurement Institure here

Using the information on your VIN plate (located usually on your drawbar, inside your front boot, inside your tunnel boot), enter your information into the calculators below to determine the weights of your caravan

ATM

ATM can be calculated as:

GTM + Ball Weight  OR   TARE WEIGHT + PAYLOAD

Using the VIN Plate above:

2313 + 157
= 2,470kg

GTM

Pre 2020 models, GTM can be calculated as:

ATM - Ball Weight

Using the VIN Plate above:

2470 - 157
= 2,313kg

2020 models and onwards, GTM can be calculated as:

Axle Tare Weight + 90% of the Payload

Using the VIN Plate above:

(Tare - Ball weight) + [(ATM - TARE) x 90%]
(1995 - 157) + [(2470-1995)*.9]
1838 + 427.5
= 2,265.5kg

Tare Weight

Tare Weight can be calculated as:

ATM - Payload

As you can see from the VIN plate shown above, the payload is not listed. Therefore the best way to find your tare weight on a new Van is a weighbridge or the weight slip found inside your manual. For a used van it is highly recommended to use a weighbridge as often modififications and extra options are fitted after purchase which then make the stamped or weighslip tare weight inaccurate.

Common Mistakes

GCM

GCM refers to the Gross Combination Mass. This is calculated as the weight of Tow Vehicle + Caravan.
This has caused confusion in recent years with the growing amount of 4×4 vehicles claiming to have 3.5T towing.

Lets use the following figures as an example:

Towing Capacity - 3,500kg
GCM - 5,850kg
Vehicle Kerbside Weight - 2,080kg 
GVM - 3,000kg

The Gross Combination Mass (GCM) minus the Gross Vehicle Mass (GVM) which is maximum legal weight of a vehicle on its own will equal the remaining legal tow capacity of the vehicle.

GCM - GVM = remaining tow capacity

5850 - 3000 = 2850

While this particular vehicle can tow 3,500kg on paper, with a fully loaded vehicle it can only tow 2,850kg. Alternatively, with 3,500kg in tow, it can carry no more than 270kg in the vehicle. Vehicle kerbside weight refers to the weight ‘at the kerbside’ i.e. full full tank, options fitted from factory, etc.
Things this won’t include are – weight of passengers, the kayaks, bikes and all the other things you pack for your holiday.

Advice

The way you pack weight into your van is important from a safety perspective. Check out this video from the Business Insider UK where they explain the effects of putting weight in different areas of the van

For any other information on weights and towing, check out the legislation applicable in your state, or head into Watsons Leisure Centre and speak to one of our friendly team.

Camping World Coffs Harbour also have scales to weigh your van from home.

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