Weight Compliance Tips

5 Weight Compliance Tips Every 4WD Owner Needs to Know

You’ve bought the dream rig. You’ve added the bullbar, the winch, the drawers, and the roof rack. You’re ready to tour the country. But before you turn the key, there is one question you need to answer: Are you actually legal?

Weight compliance is the dark horse of the 4WD world. It’s easy to get swept up in the excitement of modifications, but the reality is that most modern dual-cab utes and wagons have surprisingly low payloads once you start bolting on accessories.

As an engineer and 4WD owner, I’ve seen countless setups that look great but are dangerous and illegal on the scales. Here are my top 5 tips for keeping your rig compliant, safe, and ready for the tracks.

1. It’s Not Just About GVM (Watch Your Axles!)

The biggest misconception in the 4WD community is that if your total weight is under the Gross Vehicle Mass (GVM), you are safe. This is false.

Your vehicle has three limits you must respect:

GVM: Total weight of the vehicle.
Front Axle Limit: Maximum load on front wheels.
Rear Axle Limit: Maximum load on rear wheels.

It is extremely common to be under your total GVM limit but over your Rear Axle Limit. This happens because most touring gear (drawers, fridges, water tanks, tow ball weight) sits at the back of the car. Always check both limits—my calculator does this automatically for you.

2. Beware of the "See-Saw" Effect

Physics can be your best friend or your worst enemy. When you place heavy weight behind the rear axle (like a heavy spare wheel carrier, jerry cans, or high tow ball down-weight), it acts like a lever.

This leverage doesn't just push the rear down, it actually lifts weight off the front wheels.

Result: You lose steering traction and braking efficiency.
The Fix: Try to mount heavy items as far forward as possible. If you can move a 30kg secondary battery from the tub to the engine bay, or put your water tank in the footwell rather than the boot, you drastically improve your weight distribution.

3. Brochure Weights Are a Myth

Never trust the "Tare" or "Kerb" weight listed in your marketing brochure. Manufacturers often weigh base-model vehicles with no oil, minimum fuel, and no floor mats to make the payload look impressive.

Real-world vehicles are heavy. A "stock" LandCruiser or Ranger with a full tank of diesel, aftermarket floor mats, and a driver is often 150kg+ heavier than the brochure claims. That is 150kg of payload you lost before you even packed a sandwich.

Pro Tip: Take your vehicle to a public weighbridge with a full tank of fuel before you start your build to get a real "Base Weight." Its cheaper than you think.

4. Audit Your Gear (The "Just in Case" Trap)

We all love being prepared, but do you really need a high-lift jack, 4 recovery tracks, and a chainsaw for a weekend trip to the beach?

Weight creeps up in kilograms, not tonnes.

Steel vs. Synthetic: A synthetic rope winch saves ~10kg over steel cable.
Alloy vs. Steel: An alloy bar can save 30–40kg over a steel poster bar.
Water: 40L of water is 40kg. Fill up closer to your destination rather than hauling it on the highway for 6 hours.

5. Towing Changes Everything (The GCM Factor)

If you are towing a caravan or camper trailer, the math gets harder. You are now dealing with Gross Combination Mass (GCM).

Here is the kicker: A GVM upgrade often does not increase your GCM. If you use a GVM upgrade to load your vehicle up to 3,800kg, you might find that your remaining towing capacity has dropped significantly. You cannot simply "rob Peter to pay Paul." You must ensure the total weight of the truck + trailer does not exceed the manufacturer’s GCM limit.

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