Towing isn’t just about your car’s advertised towing capacity—it’s about how all the numbers add up: gross vehicle mass (GVM), tow ball mass (TBM), payload, and ride height. Accessories, passengers, and gear eat into your limits. If your setup isn’t right, you risk fines, insurance headaches, and unsafe driving conditions. The good news? With the right advice and adjustments, you can stay safe, legal, and confident on the road.
For the purpose of this article, “Trailer” refers to a caravan, horse float, or any other trailer.
Key Terms You Should Know
Gross Vehicle Mass (GVM)
The maximum weight your vehicle can legally carry when fully loaded. This includes passengers, fuel, accessories (bull bar, roof racks, drawers, etc.), and cargo.
Aggregate Trailer Mass (ATM)
The total weight of your trailer when fully loaded and unhitched (including water, gas, additional accessories and cargo).
Tow Ball Mass (TBM)
The downward weight your trailer applies to the vehicle’s tow ball. In most cases, TBM should be around 10% of the ATM. For example:
- Trailer ATM: 2,000kg
- Ideal TBM: approx. 200kg
Importantly, TBM is part of your GVM. This means it eats into your payload—often more than people realise.
Gross Combined Mass (GCM)
The maximum combined weight of your vehicle and whatever it’s towing. Exceeding this limit is one of the most common mistakes drivers make.
Tare Weight
The empty weight of your trailer, before loading passengers, water, or cargo.
How Payload Gets Consumed in Real Life
Imagine this scenario with a popular 4WD in Melbourne:
- Passengers: 250kg (two adults, two kids)
- Accessories: 150kg (bull bar, fridge, roof rack)
- Cargo: 100kg (bags, food, water)
- TBM: 250kg (from a loaded trailer)
That’s 750kg already, which may leave little room before you hit your GVM limit. The heavier your trailer TBM, the less capacity you have for anything else in the car.
Why Ride Height Matters
If your tow vehicle and trailer don’t sit level when hitched, you can end up with either:
- Excessively high TBM: More stress on your rear axle, reduced handling, potential axle or tyre wear.
- Excessively low TBM: Poor stability, sway, and uncomfortable driving.
Fixing Ride Height
Common solutions include:
- Adjustable tow hitches
- Weight distribution hitches
- Suspension upgrades (sometimes including GVM/GCM upgrades if legally required)
These adjustments are especially useful if you’re towing over varied terrain—whether it’s winding alpine roads or corrugated outback tracks.
Legal Responsibilities in Victoria
Here’s what matters most under Victorian law:
- Do not exceed the manufacturer’s specified towing capacity.
- Do not exceed your vehicle’s GVM or Gross Combined Mass (GCM).
- Ensure your trailer is roadworthy (brakes, lights, tyres).
- Use correctly rated tow bars and hitches.
Failing to meet these obligations can result in penalties and unsafe conditions for you and others on the road.
For official guidance, check:
Transport Victoria – Caravan Towing Rules
Practical Steps to Tow Safely
- Weigh your setup. Don’t guess. Mobile services like Weigh My Ride can weigh your tow vehicle and caravan/horse float/trailer, and/or your commercial vehicle/s at your home, anywhere in Melbourne or regional Victoria.
- Calculate payload carefully. Factor in every accessory, passenger, and bit of cargo.
- Check TBM. Ensure it’s roughly 10% of ATM and within your vehicle’s limit.
- Level your ride. Use the right hitch or suspension upgrade to maintain balance and stay within axle load limits.
- Stay legal, stay insured. Always operate within your limits to avoid legal and financial risks.
Final Word: Tow with Confidence
If you’re caravanning, travelling to a race or equine event, or hauling gear across Victoria for work, knowing what you can legally tow is non-negotiable. Don’t just rely on your car’s towing spec sheet—consider GVM, payload, and TBM in the real world.
By weighing your setup, levelling your ride, and staying within limits, you’ll enjoy safer, smoother travels.
Stay safe. Stay legal. Tow with confidence. Contact Weigh My Ride today!
