Coupling, Towball Weight & Safety Chains
Coupling and safety chain requirements are set by weight — and an enclosed trailer's extra tare means checking these against full loaded ATM matters more than it might look at first glance.
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Coupling Types
- 50mm ball hitch — approved up to 3,500kg ATM
- Pintle hook — approved up to 4,500kg ATM
Quick-release (no tools) and rated to at least the full loaded weight, in both cases.
Towball / Coupling Weight
General guidance sits around 8–12% of ATM. Always defer to whichever of the vehicle, tow bar, coupling or hitch has the lowest rating — that's the real ceiling regardless of the trailer's design percentage.
Safety Chains
| Loaded ATM | Requirement |
|---|---|
| Up to 2,500kg | At least one safety chain complying with AS 4177.4-2004 |
| 2,500kg – 3,500kg | Two safety chains, rated to 3,500kg |
| Over 3,500kg | Two safety chains, steel with minimum 800 MPa breaking stress |
Compliance note Coupling, towball weight and safety chain figures reflect Queensland Government towing requirements and Variant Trailers Australia's published specifications. Requirements can vary slightly by state — confirm against your specific vehicle and trailer compliance plates before towing.
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Questions & Answers
What coupling do I need for an enclosed trailer?
A 50mm ball hitch up to 3,500kg ATM, pintle hook to 4,500kg — calculated against the trailer's full loaded ATM, which includes its own tare weight (higher than an equivalent box trailer) plus cargo.