The Trailer and the Load Limit
You are preparing to tow a box trailer with a loaded sedan. Your sedan's owner's manual states a maximum braked towing capacity of 1,500 kg, a maximum ball load of 150 kg, and a GVM of 2,100 kg. The trailer's compliance plate shows a tare of 320 kg and an aggregate trailer mass of 1,000 kg. You load the trailer with 700 kg of gear, placing most of it behind the axle to keep the ball weight light. Your car's current kerb weight plus passengers and luggage is 1,950 kg. The trailer has no brakes. The tow ball sits about 30 mm too high, so the trailer rides slightly nose-up.
1. Is this combination legal and safe to tow? Work through the numbers.
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Several problems appear when you check the figures.
- Trailer mass. Tare 320 kg + 700 kg load = 1,020 kg. That exceeds the trailer's aggregate trailer mass of 1,000 kg, so the trailer is overloaded even before the car is considered.
- Car's GVM. The car is at 1,950 kg before adding ball load. Adding roughly 100–150 kg of ball load pushes it toward or past the 2,100 kg GVM. You need to confirm the ball load and total mass on a weighbridge.
- Brakes. A trailer of this mass generally requires its own brakes in most Australian jurisdictions; an unbraked 1,000 kg trailer behind a sedan is a serious stopping-distance problem. Confirm the local requirement, but treat it as unsafe regardless.
- Ball load. Loading gear behind the axle reduces ball weight but promotes sway. You want roughly 10% of trailer mass on the ball - around 100 kg here - within the 150 kg limit, with heavier items over the axle.
- Nose-up attitude. A trailer riding nose-up affects stability and braking. Correct the coupling height.
Conclusion: not legal or safe as loaded. Redistribute and reduce the load, fix the coupling height, and confirm brake requirements before towing.
2. How would you redistribute the load and adjust the setup before departure?
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- Reduce total load so the trailer is at or below 1,000 kg ATM - remove about 20 kg or more, and leave margin.
- Move heavy items over or slightly ahead of the axle to build a ball load near 10% of the trailer's mass (roughly 90–100 kg), staying under the 150 kg ball limit and watching the car's GVM.
- Weigh the combination - trailer mass and ball load - rather than estimating.
- Lower the tow ball so the trailer sits level or slightly nose-down.
- Check brakes and lights - confirm the trailer's braking requirement is met and that indicators, brake lights and the coupling are secure.
- Check tyre pressures on car and trailer for the load, and confirm mirrors give a clear view behind.
After departure, stop after a short distance and re-check the coupling, chains and load security.