Box Trailer FAQ
The full question bank from every section of this guide, plus general buying questions, in one place.
Buying a Box Trailer
See the full guides for detail: sides & configurations, axle types, and materials each cover one part of the buying decision in depth.
Questions & Answers
What size box trailer should I buy?
Match the trailer's GTM/ATM rating to the heaviest realistic load, not just the floor dimensions you think you need — an undersized-capacity trailer that looks the right size on paper is still the wrong trailer if it can't legally or safely carry what you actually load into it.
Do I need brakes on my box trailer?
Only if loaded GTM exceeds 750kg. Above that it's a legal requirement — full detail in the braking systems guide.
What's the difference between ATM and GTM?
ATM (Aggregate Trailer Mass) is the total loaded trailer weight including what's transferred to the tow vehicle at the coupling. GTM (Gross Trailer Mass) is only the portion sitting on the trailer's own wheels — VSB1 braking requirements are set by GTM specifically.
Single, tandem or tri-axle — which do I need?
Single axle for lighter domestic/trade loads and easier low-speed manoeuvring; tandem for higher capacity and better highway stability; tri-axle only for heavier commercial/specialist loads near the top of the light-trailer weight bracket.
Galvanised steel or aluminium?
Galvanised steel for strength, impact resistance and long-term corrosion protection including welds and internal surfaces. Aluminium for lower tare weight and easier handling, at the cost of dent resistance and repair simplicity. Both materials are used by Australian and imported manufacturers — check the individual trailer's spec, not its country of origin.
What coupling do I need?
A 50mm ball hitch covers trailers up to 3,500kg ATM; a pintle hook extends that to 4,500kg ATM. Either must be quick-release (no tools) and rated to at least the trailer's full loaded weight.
How many safety chains does my trailer need?
One AS 4177.4-2004 chain up to 2,500kg loaded ATM; two chains rated to 3,500kg between 2,500–3,500kg; two chains of minimum 800 MPa steel above 3,500kg.
How far can a load overhang the trailer?
No more than 150mm beyond the sides, 2.5m overall width, and a red flag (min. 300mm square) required if the load projects more than 1.2m beyond the rear.
Do I need an electric brake controller?
Only if the trailer has electric or electric-over-hydraulic brakes. Mechanical overrun brakes — fully compliant up to 3,500kg — need no electrical connection to the tow vehicle at all beyond standard lighting.
Is a sign-written trailer worth it for a trade business?
Generally yes — it turns time the trailer already spends parked and driving into ongoing advertising exposure at a cost typically recovered many times over. See the signage guide for what to include and material choice.