Rigs must comply with weight restrictions. PIC: Weightcheck Mobile Caravan Weighing
Dave Lewis from Weightcheck Mobile Caravan Weighing – which is based in Brisbane but has  partner companies in Melbourne and Perth, and will shortly have an operation in New South Wales – offers his insight into common caravan weight issues
There are six compliances that need to be checked when completing our weighing reports. The Towball Mass (TBM), Gross Trailer Mass (GTM) and the Aggregate Trailer Mass (ATM) of the caravan, and the Braked Towing Capacity (BTC), Gross Vehicle Mass (GVM) and Gross Combination Mass (GCM) of the tow vehicle.
Our statistics to-date show some alarming results, with 31% of tow vehicles, and 63% of caravans we have weighed, have been overweight.
The most concerning noncompliance report we have completed was on a dual cab utility and large off-road caravan. The caravan was 411kgs over its ATM, and the tow vehicle 454kgs over its GVM, bearing in mind this also means that the vehicle is 411kgs over its 3500kgs BTC as well. The whole rig was a staggering 1012kgs over its GCM.
The most common weight issue we see is exceeding the ATM of the caravan, which is not hard to do. The available payload of a van is the difference between the TARE and ATM recorded on the compliance plate, with most tandem axle vans having upwards of 400kgs available. The payload includes water, gas, gear, food and clothes, and it doesn’t take very long to add up.
The Towball Mass is also very important and affects the stability of the towed caravan. Ball weight should be around 10% of the caravan ATM and a light ball weight will make the caravan sway, so it’s very important to get the distribution of payload correct. The towball weight also contributes to the GVM of the tow vehicle, and we are seeing an increasing number of tow vehicles that are exceeding their weight compliance.
The GVM is the total fully loaded weight of the vehicle including passengers, fuel, cargo, and any extras like bull bars, roof racks etc that have been added, plus the caravan TBM. For instance, one of the most popular tow vehicles with a towing capacity of 3500kgs has a payload of 630kgs, so if you add a bull bar, fridge, two passengers, 120 litres of fuel and the caravan TBM of around 300kgs, you will probably be over the GVM.
Therefore it is very important to get your tow vehicle weights checked as well. Don’t forget, an overweight caravan is classified as an unroadworthy vehicle, the same as a car with a bald tyre, so for legal and insurance reasons it is very important to ensure your rig is compliant.
I have a challenge for caravan manufacturers and inventors out there. Can somebody develop a system that is hard wired into the caravan that tells me my current ATM and the tow ball mass. Just measuring the weights once off is helpful but not the answer. The weights and balances change on your trip. Fresh water tanks empty, grey water tanks fill up, gas bottles empty, contents are repositioned, another slab of beer and the freeze full of fish ( I wish). The output display would need to be visible from outside the van as my weight shouldn’t be included in the measurements 🙂
I beleive that tare weight should include mattress, full gas bottles and water tank full. Then it would be easier for most people to account for weight added.
The idea of having something that can visibly indicated the weight of the van would be excellent the weight of the car is fairly easy to do at a tip site but not every area has access to truck scales
I have a windsor caravan with a gtm of 2064. The chassis plate is rated to 2750 . I used a vehicle engineer to inspect the van and design an upgrade which was to cut off the stiffening bar from under the drawbar both sides. Then weld under each draw bar a 50x50x3mm tube increasing the bar from a 100mm to a 150mm deep bar. He then checked the modification and issued a new plate to replace the one in the front boot. I now have a gtm of 2750 and with the 10% ball weight an atm of 3025. The problem is when caravans were first made the empty weight would be the tare then add on 400kg for the gtm. This formula is still used today. I won’t be loading my van to full capacity but just happy to be legal as i was just over last time i checked. Happy vanning Mike