Buying guide
Towing set-up explained
Safe towing comes down to a few numbers on your trailer and your vehicle. Here's how they decide what brakes, controller and towbar you need.
- GTM decides the brakes
Trailer brake rules use the trailer's GTM (the mass on its axles), not its ATM. Up to 750 kg GTM, no brakes are needed. Over 750 kg the trailer needs brakes, and electric brakes need a controller in the vehicle.
- Over 2,000 kg
All wheels must be braked, with a breakaway system that applies the brakes immediately and holds them for at least 15 minutes if the trailer comes off (VSB 1).
- The lowest rating wins
Your towing limit is the lower of the towbar's rating and the vehicle's rating. The tow ball weight counts towards your vehicle's GVM.
- The right plug
On a 7-pin plug, pin 5 is for brakes only. If the van needs power for a fridge, use a 12-pin plug or an Anderson connection.
Choosing a Tow Ball Mount
The goal is a trailer that tows level. Measure the height of your trailer coupling with the trailer sitting level, compare it to the height of your towbar, then choose a mount with the drop or rise that closes the gap. A trailer that rides nose up or nose down puts uneven load on the axles and can affect braking and sway.
Ratings matter as much as fit. Your towing setup is only as strong as its lowest rated component, so check that the mount's rating covers your loaded trailer weight, and confirm it matches your towbar's tongue and your tow ball size. Most Australian couplings use a 50mm ball, but always check your own gear rather than assuming.
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Common questions
When does my trailer need electric brakes?
Brakes are required once the trailer's GTM is over 750 kg. Over 750 kg the brakes must work from a controller in the vehicle unless they are override (over-run) brakes, which are only allowed up to 2,000 kg. Over 2,000 kg every wheel must be braked, plus a breakaway system (VSB 1).
What's the difference between ATM and GTM?
ATM is the trailer's total mass when loaded, including the weight on the tow ball. GTM is the mass carried by the trailer's own axles. ATM minus GTM is the tow ball download. Both are maker ratings, not weighbridge readings.
Proportional or user-controlled brake controller?
A proportional controller brakes the trailer in step with the vehicle and suits most on-road towing. User-controlled (time-based) braking gives you manual control, which Redarc recommends for sand and steep descents.
What is a breakaway system?
A battery-powered system on the trailer that applies its brakes if it separates from the vehicle. It's required over 2,000 kg and must hold the brakes for at least 15 minutes (VSB 1).
How much tow ball weight should I have?
Guidance ranges from about 5 to 10 percent of the trailer's weight. It counts towards your vehicle's GVM and must stay within the towbar's and vehicle's tow ball limits.
How many safety chains does my trailer need?
One chain built to AS 4177.4 up to 2,500 kg ATM, and two above that (VSB 1).