Car trailer dimensions in Australia explained

If you’ve ever had to transport a car – either yours or someone else’s – via a trailer you’ll know the importance of getting the car trailer dimensions spot-on. You really don’t want the combination to be illegal or unsafe.

The vehicle needs to be able to cope with the trailer and the planned load, whatever vehicle that is; it’s not advisable to try towing a loaded dual car trailer with your Kia Picanto. In fact, it’s illegal, not to mention downright silly.

Standard trailer sizes in Australia depend on whether your need a small car trailer, a two car trailer, a dual axle car trailer, a flatbed car trailer, a hydraulic car trailer or something else entirely.

The trailer needs to match the job, because, for example, a lightweight car trailer and a dual car trailer are engineered to cope with different maximum loads, but more about weights soon.

What are car trailer dimensions and why are they important?

Trailer measurements or dimensions are crucial because by knowing the car trailer size (including but not limited to the car trailer length and the car trailer width) as well as the car trailer weight, you’ll be well on your way to understanding whether your tow vehicle and the trailer are legally able to do the job and indeed up to the task you’re about to burden them with.

Before you bother sizing up a car trailer, make sure you know the measurements and dimensions of the trailer vehicle, i.e. the vehicle you’re planning to put on the trailer. Throw the vehicle on your nearest weighbridge and get your tape measure out because you need to know the vehicle’s overall length, width and how much ground clearance it has.

Car trailer dimensions in Australia are varied, but as an approximate car trailer size guide a decent reference is to know car trailers can range anywhere from a 3000mm-long deck (the flat portion on which the car sits) to a 4600mm-long deck, or big units at 5700mm or even 6000mm. (Note: that deck length does not, of course, include the drawbar length.)

If you need maximum protection for your towed vehicle, you’ll have to consider getting an enclosed car trailer, and if that’s the case you’ll need to know the vehicle’s height, so it’ll actually fit inside the trailer.

Another crucial consideration is the maximum weight the tow vehicle can legally tow, and the maximum weight the trailer can legally have onboard. When deciding on a trailer or checking out a car trailer for sale there are some important weights to be aware of…

First consideration: the tow vehicle. Towing capacities are in terms of unbraked (trailer does not have in-built braking system) and braked.

A vehicle’s unbraked figure may range from 400kg to 750kg (depending on the size and type of vehicle) and the braked* figure can range up to 3500kg (for mainstream SUVs and utes) and even more for US utes in Australia.

For example, the Ram 3500 Laramie can legally tow up to 8000kg** (braked).

* Trailer does have its own independent onboard braking system.

** To tow anything more than 4500kg you need a truck licence.

According to Transport NSW, “the minimum braking system for a trailer depends on the type of trailer, its weight and the weight of the vehicle" as follows:

0 – 750kg loaded weight – no brakes required. [referred to as 'unbraked']

751 – 2000kg loaded weight – braking on both wheels on at least one axle. ['braked']

2001 – 4500 kg loaded weight – braking on all wheels, and an automatic breakaway system in case the trailer becomes detached from the vehicle ['braked']

Second consideration: the trailer. Tare Trailer Mass or Weight (Tare) is the weight of an empty trailer. The term 'trailer' covers everything you can tow or 'trail' behind a vehicle, from a single-axle box trailer or camper trailer to motorcycle and jet-ski trailers right on up to heavy duty multi-axle boat trailers and caravans.

If it's a camper trailer or caravan, its Tare Mass unlike a motor vehicle does not include fluids like water tanks, LPG tanks, toilet systems. Also known as Dry Weight, for obvious reasons.

Gross Trailer Mass (GTM) or Weight (GTW) is the maximum axle load that your trailer is designed to carry as specified by its manufacturer.

It is the combined weight of your trailer and its payload, but does not including the Tow Bar Download (see separate heading). The GTM is usually displayed on the trailer or in the owner's manual.

Aggregate Trailer Mass (ATM) or Weight (ATW) is the Gross Trailer Mass (GTM) plus the Tow Bar Download (see separate heading). In other words, the ATM is the maximum towing weight of the trailer/caravan as specified by the manufacturer.

Gross Combination Mass (GCM) or Weight (GCW) is the maximum weight allowed for your vehicle and trailer combined, as specified by the tow vehicle's manufacturer.

Pay close attention to your vehicle's GVM (gross vehicle mass) and your trailer's ATM, because those two figures determine the GCM and one directly affects the other.

 

How and why do car trailer dimensions differ? Do Australian dimensions differ from overseas?

Car trailer dimensions in Australia do differ, because they are engineered for different jobs/loads. Some haul cars, some haul farm machinery, some haul horses, etc.

Car trailer dimensions in Australia may differ from overseas trailers because of the different sized vehicles that do the towing and are towed. The US, for instance, has a plethora of big pick-up trucks, and they’re able to tow larger maximum loads than most of the mainstream utes in Australia.

 

How important is car size to the dimensions of a car trailer? What aspects need to be considered in the sizing?

The vehicle must fit comfortably onto the trailer. There must be room enough to open and close the driver’s door, the tie-down points must be easily accessed when the car is on the trailer, and you must be able to operate the trailer’s onboard vehicle restraints.

It’s crucial to be aware that a vehicle's towing capacity is reduced when taking into account how much of a load the tow vehicle itself has onboard (passengers, aftermarket mods, camping equipment, etc).

And – remember this – the vehicle-and-trailer combination always has to weigh within the Gross Combined Mass (GCM) limit, that is the maximum your vehicle-and-trailer combination can legally weigh.

It's also important to keep in mind your vehicle's real-world weights, including its tare mass (a vehicle's weight when it is empty or unladen), ball load (how much weight a trailer or caravan imposes on your tow ball when it is hitched to your vehicle and the jockey wheel is not taking any weight), as well as things such as aggregate trailer mass, which the RACQ describes as "the combined weight of the trailer and its full load when it is not coupled to a tow vehicle".

As mentioned earlier, before you tow anything over any substantial distance, use your local weighbridge to get an accurate idea of the weight of your vehicle and trailer to make sure you're driving within legal limits.

 

Common car trailers and their dimensions in Australia

Standard trailer sizes in Australia vary depending on what you need the trailers for.

Small car trailer

A small car trailer (aka flatbed car trailer) will likely be about 6200mm long (including drawbar) and 2500mm wide. Materials for any trailer are usually, steel and/or aluminium. Most car trailers have leaf-spring suspension, though some use torsion axles and air-bag suspension.

The trailer should be equipped with, at the very least, ramps, working tail-lights and number plate light, a seven pin flat plug, compliance plate etc.

Prices start from around the $5000 mark for an open floor car trailer and range up to $10,000 and beyond.

 

Two car trailer

A two car trailer (aka dual axle car trailer, tandem, or flatbed car trailer) will likely be 7000mm long or more (including drawbar).

Materials for any trailer are usually, steel and/or aluminium. The trailer should be equipped with, at the very least, ramps, working tail-lights and number plate light, a seven pin flat plug, compliance plate etc.

Prices start from around the $6000 mark for an open floor car trailer and range up to $11,000 and well beyond.

 

Hydraulic car trailer

A hydraulic car trailer is simply a car trailer that has an inbuilt hydraulic system to raise and lower the tilting flat deck of the trailer. It may be up to 7000mm long or more (including drawbar).

Materials for any trailer are usually, steel and/or aluminium. The trailer should be equipped with, at the very least, working tail-lights and number plate light, a seven pin flat plug, compliance plate etc.

Prices start from around anywhere near the $5000 mark for a hydraulic tilt car trailer and range up to $11,000 and beyond.