Living in a caravan:
Hot Tip number 3.
Tow weights!!!
Taking a step back for a sec to explain a few things about tow weights.
It’s a subject that is poorly misunderstood but super important. I recall taking a significant amount of time making sure I understood it correctly particularly when we were on the search for a caravan.
My particular issue at the time was understanding the weight restrictions of my tow vehicle. I was about to drop significant sats on a van, I didn’t want to be forced into upgrading my tow vehicle as well. Importantly I knew my vehicle engine was more than capable, but the chassis rating, towable capacity and tow ball weight ratings were the issue.
My specific issue:
My vehicle is rated to tow 3000kg. With a caveat!!!
IF the weight of the towed mass exceeds 2500kg the tow ball weight rating drops from the standard 250kg down to 180kg.
Here’s the thing…. When towing large masses you WANT tow ball weight. Tow ball weight makes for stable towing and less sway. Many people misunderstand the importance of tow ball weight and some are even guilty of shifting things around in their van to relieve some of this weight. Here is a video to demonstrate.
Therefore: I needed to find a van that was light enough for me to tow, fully loaded that did not exceed 2500kg so that I could have the full 250kg available in the ball.
A good rule of thumb is around 8-10% of the trailers mass you want on the ball.
So this sent me on a path of understanding everything from Tare weights to payloads to GCMs and ATMs…
My summary is below….
It is fully worth your time understanding and making sure you and your vehicle are within these guidelines. You can be fined, you can have insurance denied but more importantly you can be putting your family at risk if you don’t understand and pack your van effectively.
So here are a few acronyms and explanations to help paint a picture.
Vehicle & Caravan Nameplate Measures (Towing Terminology)
1. Gross Vehicle Mass (GVM)
Definition: The maximum allowable weight of a vehicle when fully loaded, including passengers, fuel, cargo, and accessories. (This include tow ball weight)
• Set by the manufacturer.
• Exceeding GVM can cause safety and legal issues, especially when it comes to insurances and liability.
2. Gross Combination Mass (GCM)
Definition: The maximum allowable combined weight of a fully loaded vehicle (GVM) and a fully loaded trailer or caravan.
• Also set by the vehicle manufacturer.
• Ensures that the towing vehicle and caravan together do not exceed safe operating limits.
3. Payload
Definition: The maximum weight of cargo, passengers, and accessories that a vehicle or caravan can legally carry

• This includes passengers, luggage, tools, fuel, and any modifications (such as bull bars, winches, etc.).
4. Tare Mass (Tare Weight)
Definition: The weight of the vehicle or caravan as supplied by the manufacturer, with all standard equipment, fluids (including oil and coolant), and an empty fuel tank.
• Vehicle Tare Mass: Does not include passengers, cargo, or accessories.
• Caravan Tare Mass: Does not include water in tanks, gas bottles, or personal belongings.
5. Kerb Weight
Definition: The weight of a vehicle with a full tank of fuel but without passengers, cargo, or additional accessories.
• Often confused with Tare Mass but includes a full fuel tank.
6. Tow Ball Mass (TBM) / Tow Ball Download (TBD)
Definition: The downward force exerted by the caravan or trailer onto the tow ball of the towing vehicle.
• Typically 8-15% of the trailer’s total weight.
• Must be within the vehicle’s tow ball mass rating.
7. Maximum Braked Towing Capacity
Definition: The maximum weight a vehicle can tow when the trailer or caravan is fitted with its own independent braking system.
• Specified by the vehicle manufacturer.
• Usually much higher than the unbraked towing capacity.
8. Maximum Unbraked Towing Capacity
Definition: The maximum weight a vehicle can tow when the trailer or caravan has no brakes.
• Limited by Australian regulations to 750 kg for most passenger vehicles.
9. Aggregate Trailer Mass (ATM)
Definition: The total maximum weight of a fully loaded caravan or trailer when it is NOT attached to a tow vehicle.
• Includes water, gas, cargo, and accessories.
Formula:

• Exceeding ATM can lead to fines, mechanical stress, and insurance issues.
10. Gross Trailer Mass (GTM)
Definition: The total weight of a fully loaded caravan or trailer when it IS attached to the tow vehicle.
Formula:

• GTM is measured at the caravan’s wheels (not including the tow ball weight).
11. Maximum Axle Load Rating
Definition: The maximum weight that each axle of a vehicle or caravan can safely support.
• Exceeding axle limits can lead to suspension, braking, or tyre failures.
12. Gross Axle Weight Rating (GAWR)
Definition: The maximum allowable weight that each axle (front and rear) of a vehicle can support, including the vehicle weight and any cargo.
Summary of Key Relationships
• GCM = GVM + GTM (Total weight of the vehicle and trailer cannot exceed this.)
• ATM = GTM + Tow Ball Mass (How the total trailer weight is distributed.)
• Payload = GVM - Tare Mass (How much a vehicle can carry before exceeding GVM.)
• GTM ≤ Caravan’s Axle Load Rating (Ensures that the caravan’s suspension and tyres can handle the weight.)
Thanks for coming to my TED talk.
