Plenty of utes and large SUVs sold in Australia are advertised with a 3,500 kg braked towing capacity. It’s a real figure, but it comes with a condition that brochures rarely spell out: the vehicle and trailer together must stay under the vehicle’s gross combination mass (GCM). On many vehicles, the GCM runs out before the towing capacity does.
The arithmetic
GCM is the most the loaded vehicle and loaded trailer may weigh together. So the heaviest trailer you can tow is:
Maximum trailer = GCM − loaded vehicle weight
up to the towing capacity, whichever is lower.
Now look at a typical set of figures for a dual-cab ute:
- GCM 6,000 kg
- GVM 3,200 kg
- Braked towing capacity 3,500 kg
GVM plus towing capacity is 3,200 + 3,500 = 6,700 kg. The GCM is 6,000 kg. The 700 kg gap means you can’t load the ute to its GVM and tow 3,500 kg at the same time.
To tow the full 3,500 kg, the loaded ute must weigh no more than 6,000 − 3,500 = 2,500 kg. If its kerb weight is around 2,200 kg, that leaves about 300 kg for the towbar, accessories, passengers and gear, and the towball download still has to fit under GVM too.
Load the ute to its full 3,200 kg GVM and the heaviest trailer it can tow is 6,000 − 3,200 = 2,800 kg.
Motoring writers have pointed out this pattern for years, for example in Practical Motoring’s explainer on 3,500 kg tow ratings. The exact numbers vary by model and variant, so always use the figures for your own vehicle.
How much each kilogram costs
Once you’re past the point where GCM starts to bind, every kilogram you add to the vehicle is a kilogram you can’t tow. For the ute above:
| Loaded vehicle | GCM allows | Heaviest trailer |
|---|---|---|
| 2,500 kg | 3,500 kg | 3,500 kg |
| 2,700 kg | 3,300 kg | 3,300 kg |
| 2,900 kg | 3,100 kg | 3,100 kg |
| 3,100 kg | 2,900 kg | 2,900 kg |
A bull bar, canopy and drawers, a family of four and a weekend’s gear can easily put a dual-cab at 2,900 kg or more. The how much can I tow calculator shows this for your own figures.
It isn’t only GCM
Two other limits can cut in before the towing capacity:
GVM through the towball. The trailer’s towball download sits on the vehicle. If your vehicle is already close to GVM, the room left divided by the towball percentage limits the trailer. With 150 kg left under GVM and a 10% towball download, the trailer can’t weigh more than 1,500 kg.
Maximum towball download. If your vehicle allows 350 kg on the towball and your caravan carries 12% of its weight there, the heaviest caravan you can tow is 350 ÷ 0.12 = about 2,917 kg.
The calculator works out all four limits and tells you which one sets your maximum.
What you can do about it
Weigh first. A public weighbridge tells you what your vehicle really weighs as you travel. Start there rather than from brochure figures. Our weighbridge calculator turns the readings into the numbers you need.
Move weight from the vehicle to the trailer. Gear in the caravan instead of the ute tray counts against the caravan’s ATM rather than the vehicle’s GVM. The combined weight doesn’t change, so this helps with GVM but not with GCM. It only works if the caravan has payload to spare. The caravan payload calculator checks that.
Travel with less water. Water is about 1 kg per litre. Filling tanks near camp instead of at home can free up 100 kg or more.
Strip unnecessary weight. Steel bull bars, heavy drawer systems and spare gear you never use all count.
Look carefully at upgrades. Some GVM upgrades come with a GCM upgrade and some don’t. An upgrade that raises GVM without raising GCM lets you carry more in the vehicle, but every extra kilogram in it still comes off what you can tow. Check the paperwork for the upgraded GVM, GCM and towing figures before you rely on them.
Choose the vehicle for the trailer. If you’re buying, compare GCMs as well as towing capacities. Two vehicles both rated to 3,500 kg can have very different GCMs.
Common questions
Is it illegal to exceed GCM if I’m under GVM and the towing capacity? Yes. Each rating is a separate limit and you must stay under all of them.
Does the towball download count twice? No. For GCM you add the vehicle and trailer weighed separately. The towball download moves weight from the trailer’s wheels to the vehicle, but the total stays the same.
Where do I find my GCM? In the owner’s manual or the manufacturer’s specifications for your exact variant. Some vehicles also show it on the compliance plate.