When it comes to caravan towing weights, the GTM weight on a caravan is one that you will need to know and understand.
While both the GTM and ATM are the weight of the fully loaded caravan, one must be measured while hitched up to the caravan, while the other is taken as the unhitched weight.
Here is everything you need to know about your caravan GTM weight.
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Caravan GTM Explained
Caravan GTM Weight (or Gross Trailer Mass) is the weight of a fully loaded caravan when it’s hitched up to the tow vehicle.
The GTM, which is set by the manufacturer for your caravan, is the maximum axle load that your trailer is designed to carry and must not be exceeded.
Therefore, the GTM weight on your caravan may be lower than the figure set by the manufacturer, but it must never be higher.
The definition set by the Australian Government in the Vehicle Standards Bulletin 1 (VSB1) says:
12.6 Gross Trailer Mass (GTM)
GTM is the mass transmitted to the ground by the tyres of the trailer when coupled to a towing vehicle and carrying the maximum load recommended by the manufacturer or importer, approximately uniformly distributed over the load bearing area.
In other words…
Caravan GTM is the maximum allowable weight of the caravan when hitched up to a tow vehicle (as recommended by the manufacturer) with the load being evenly distributed over the axles.
Where to Find Your GTM
You should be able to find your caravan GTM weight stamped onto the caravan compliance VIN plate. The VIN plate can usually be found just inside the caravan door, on the drawbar or inside the front boot.
This is the maximum weight that your caravan is allowed to be when hitched up to the tow vehicle.
What Does Caravan GTM Weight Include?
The GTM includes everything that makes up the weight of the fully loaded caravan hitched up to the tow vehicle.
This includes all accessories, modifications, luggage, gas and water.
Caravan GTM Weight Includes:
- Upgrades (solar system, additional water tanks etc.)
- Camping furniture
- Water tank contents
- Waste tank contents (black water, grey water & toilet cassette)
- Hot water system contents
- Gas & gas bottles
- Food & drinks
- Cooking gear
- Toys, bikes, scooters, games, books etc.
- Personal items (toiletries etc.)
- Camping furniture (chairs & tables)
- BBQ & accessories
- Jerry cans & holders
- Tools, toolboxes & maintenance gear
- Hoses & leads
- Levellers & chocks
- Annex walls/ privacy screens
- Outdoor matting
… and anything else that is loaded into the caravan
How to Work Out Your Caravan’s GTM
To find out the GTM of your caravan, you will need to hitch up the van and drive to a Public Weighbridge to weigh it using the instructions below.
Remember, you are weighing the fully loaded weight of your caravan while it is hitched up to the tow vehicle. You need to make sure this weight comes in under the GTM weight specified by your caravan manufacturer (which is on the VIN plate).
How to measure the GTM:
- Ensure the vehicle and caravan are both fully loaded
- Drive the vehicle off the scales, but leave the caravan still on the weighbridge
- Keep the caravan hitched up to the vehicle
- Record the weight
- This needs to be lower than the manufacturer stated GTM
Another way to work out your GTM is by taking the maximum allowable weight of the caravan (ATM) and minus the tow ball weight (TBW). The reason we subtract the TBW is because the car is now carrying that weight, which was previously included in the ATM.
If you’re not sure how to find your tow ball weight, check out the three different options below.
What to Do if You’re Over Your GTM
If you’ve found that your caravan is over its GTM weight when you weigh it, you’ll need to take things out of the van until you can get it under the manufacturer-specified GTM.
The GTM represents the maximum weight that the caravan is allowed to be when it’s hitched up to the tow vehicle.
Go through all of the contents of the caravan and pull out anything that isn’t necessary. You could consider removing any accessories that you just don’t use, such as toolboxes, extra jerry can holders, bike racks, TVs etc.
Another way to reduce your caravan’s GTM weight is by draining the water out of the water tanks. Full water tanks can frequently push people over their towing weights given how fast the weight of water adds up!
1 litre = 1 kilo
Once you’ve emptied out as much unnecessary weight as you can, you’ll need to head back to the weighbridge and re-weigh your caravan (using the same instructions as above).
Hopefully, you’re now under your caravan GTM weight, but if not, it’s back to the culling until you can achieve the figure that you need.
Caravan GTM FAQs
No, GTM (Gross Trailer Mass) and GVM (Gross Vehicle Mass) are not the same thing.
GTM is the weight of the fully loaded caravan, hitched up to the tow vehicle, while GVM is the weight of the fully loaded vehicle. Both the car and the caravan will have maximum allowable GTM and GVM weights, as specified by their manufacturers.
ATM (Aggregate Trailer Mass) is the maximum allowable weight of the fully loaded caravan unhitched from the tow vehicle. GTM (Gross Trailer Mass) is the weight of the fully loaded caravan hitched to the tow vehicle.
To work out the GTM weight, you take the maximum allowable weight of the caravan (ATM), minus the tow ball weight (TBW). GTM = ATM – TBW
No, GTM does not include the tow ball weight. As GTM is the weight of the caravan (fully loaded) when its hitched up to the tow vehicle, the ball weight has now transferred to the car.
Use the Caravan Packing List below to keep track of what you have packed into the caravan and use the ‘weight’ section to organise your payload.
Caravan Packing List
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