When you weigh things up…

There’s been a bit of press lately about the importance of vehicle and trailer weights, with authorities starting to enforce this important aspect of vehicle road worthiness.

While the TVAN is comparatively light compared to a caravan it has a relatively high hitch weight and with some big trips planned it was time to get the rig weighed. I’ve been running a spreadsheet for some time to calculate vehicle weights but in the case of the TVAN I have relied on the manufacturer’s data, putting the rig over a set of scales would give me an accurate base line for the current configuration and changes we make in the future.

We chose a local mobile weighing service and can highly recommend Ben from Mobile Weight Check if you are in the Brisbane area. Our driveway is too steep for the exercise so we met Ben at a local sportsground car park to do the deed.

I deliberately loaded up the Cruiser and TVAN for the exercise, with full fuel and water tanks, recovery gear, all spare tyres and even the bike rack and mountain bike.

The weigh-in involves quite a few steps to accurately measure mass carried by each wheel and axle of the car and trailer, with and without the trailer hitched to the car.

The 200 Series has a GVM (Gross Vehicle Mass) upgrade from the standard 3,350kg to 4,015kg, giving significantly more payload than a stock Landcruiser. However the Cruiser has a lot of added accessories including being set up for solo travel with its own fridge, 12V oven and lots of storage, which I filled with tools and spares. The Cruiser also has a long range (215l total) fuel tank and its own 55l water tank, plus two spare wheels on the rear bar. I suspected that our problem would not be exceeding the allowable GVM of the car or trailer, but overloading of the Cruiser’s rear axle…

The rear axle of any vehicle is easily loaded when towing because the hitch is so far behind the axle, leading to a cantilever effect that multiplies the weight seen at the axle. In the case of a 200 Series Landcruiser this means that 200kg of hitch weight increases to nearly 300kg of axle loading, think of it like a see-saw effect as illustrated below:

Based on all of the above factors it was no surprise that the TVAN was well within its 1,800kg ATM (Aggregate Trailer Mass) rating, but the Cruiser had exceeded its GVM with the trailer hitched, and the car’s rear axle was overloaded.

The short term remedy to this situation was to drain all water from the Cruiser tank and the TVAN front tank, and to relocate some of the TVAN contents to rear of the trailer in order to reduce ball weight. That would at least make us legal on the day, until we burnt off some fuel.

Usually when we are touring I don’t take the bike (bike + carrier = ~50kg) and we don’t carry the extra spare tyre on the TVAN (~40kg), which significantly reduces ball weight and therefore car rear axle loading.

With a few big trips coming up I am glad of the knowledge gained from the weight checking process. I can now update my loading spreadsheet to ensure we not only remain legal, but that we are not overloading and stressing the Cruiser and TVAN any more than necessary on the rough tracks we often traverse.

This information is useful not just for determining legal axle loads, but also for calculating optimum tyre pressures to run, deciding on best way to load the car and trailer and selecting recovery equipment that is suitably rated for the vehicle mass. All of this makes for a more reliable rig and a safer journey.

I highly recommend that all overland travellers take the time to get your rig weighed and set your self up for success in your journey.