Effects of overloading your 4x4

01/11/2019

Bent chassis, overloaded, gvm, gcm, gross vehicle mass, gross combination mass, gvm upgrade, cab chassis, ball weight, towing capacity, tare mass, tow ball weight, ball weight scale, combination mass, tow ball

Coming up on Summer, it’s the great Australian dream to pack friends, family, the dog, and all the camping gear in the car, strap a trailer, caravan or boat onto the back and head off. Not a whole lot of us take the time to think just how much weight we’re loading our vehicles up with, and it’s a bigger safety issue than you think.

Toyota heading down rocky beachside trail

How easy is it to overload my 4x4?

For example let’s take the 2019 Ford Ranger, the latest in a line of best-selling vehicles across Australia and a favoured vehicle for the weekend warriors. These specifications are taken straight from the Ford Australia webpage.

The 4x4 XL Double Cab Chassis 3.2 Diesel, with an automatic gearbox, has a kerb weight (tare mass) of 2012kg with a full tank of diesel with a maximum GVM (gross vehicle mass) of 3200kg. The stock ute has a payload of 1188kg. Now throw into the mix:

  • Family of 4 - 240kg
  • Steel bullbar - 40kg
  • Steel undertray/gearbox bash plate - 20kg
  • Dual battery setup, catch can, snorkel, other mods such as driving lights, etc - 30kg
  • Side steps - 30kg
  • ‘Service body’ style lockable canopy - 100-200kg
  • 80 litres of drinking water in container - 80kg
  • Full length aluminium roof rack - 20kg
  • Clothes for 7 days - 30kg
  • Tent, camp chairs, cooking stove - 60kg
  • Gas bottles - 9kg ea.
  • Two full size spare tyres mounted on alloy rims - 35kg ea.
  • Miscellaneous (small compressor, maxtrax, tools, first aid kit, jack, so on - 60kg)

All of a sudden, with just a few mods and the family loaded up, we’re at nearly 900 kg payload and you’re very close to the maximum weight limit. And that’s before you even consider the tow ball weight of a trailer or caravan attached (which also counts against your payload rating). It’s important to note that your insurance provider may reject a potential claim if they find your vehicle was overloaded.

Low angle shot showing caravan dolly wheel and trailer hitch

Another way of looking at this is if the Ranger has a GCM of 6000kg (gross combination mass), minus its max towing capacity of 3500kg, minus the relatively dry vehicle weight of 2012kg, this gives a payload capacity of 488kg if towing a 3500kg caravan. Out of that 488 kilos you still have to take off any accessories your cab chassis has had fitted after leaving the factory and your caravan tongue weight (which can be up to 10% of the trailer weight, so 350 kg in this case).

In practice, this rarely happens but it shows how quickly you can overload even a stout modern 4x4. The Ranger in our example has one of the higher load capacities (The 2019 Toyota Landcruiser 200 is only rated for a load of 610kg, but has a higher GCM of 6850kg).

What effects does overloading a vehicle have?

When a vehicle is overloaded, a lot of components are affected. Wheel bearings will wear quicker, as will shock absorbers. Whether your vehicle has live axle or independent suspension, extended periods of overloading can cause the suspension to permanently sag, resulting in poor handling, damaged or torn suspension bushings as well as irregular tyre wear.

Another common issue with overloading 4x4s that see a lot of action off-road is the dreaded cracked chassis. Often occurring on vehicles with lots of weight towards the back of the vehicle (toolbox canopies, twin spare tyre holders) or trailers with excessive tow ball weight. Everyone has seen the viral photos of utes with cracked and bent chassis circulating around the net, which can be what the outcome here is.

Tyres are designed with a particular maximum load in mind. Referred to as the ‘load index’ this measurement is what the tyre has been engineered to work as expected under. You can see the rating on the sidewall of your tyre as a two or three digit number which can be decoded with a table online.

While talking about tyres it is important to get your vehicle aligned while it has the amount of weight in it that you expect to be driving with for the majority of your travel. This applies to independent suspension vehicles mainly but it is important your vehicle is aligned at the ride height it will be most of the time.

When travelling at GVM or close to, items like brakes will have to work a lot harder to slow your vehicle down. Overheating brakes are a cause of a large number of 4x4 and heavy vehicles incidents.

Toyota Landcruiser towing caravan along dirt road, backlit by the sun

What can I do about it?

The first thing to do when you’re worried about your weight is to get your vehicle loaded up as you normally would and take it to a publicly accessible weigh bridge. You should ideally weigh the whole combination, as well as the vehicle and trailer separately. If this option is not available to you, most automotive stores can source ball weight scale to double check what your ball weight is.

Whether you’re a tradie looking to load up with every tool for a big job or looking to take your family away on a big trip this summer get in touch with the expert team here at Tyre Zone Capalaba. We have experienced technicians available to discuss your vehicle, your expectations, suspension upgrades for both GVM upgrading and lift kits. We also do servicing, wheel and tyre packages as well as Super Start Batteries.

Come see us at 80 Redland Bay Rd, Capalaba QLD, or phone on (07) 3245 6125

Email is available too, get in touch with us at sales@tyrezonecapalaba.com.au



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