Everything has jargon and towing a trailer is no exception. As we can’t talk about towing without knowing what we’re talking about, we’ll need to define a few terms before talking about anything else in this Ultimate Towing Guide series. We won’t explain in detail what each thing is, as that comes later. This glossary is also limited to towing, so we won’t be covering caravan-specific items such as toilets or kitchens.
This glossary is presented not in alphabetical order but in order of parts that are related to each other.
Trailer or travel trailer
That’s the thing on wheels you tow! Anything towed is a trailer, and if you can live in or out of it, then it’s a ‘travel trailer’. This is not a term often used in Australia but I think it’s appropriate.
What you use to pull your trailer. We’ll just call them ‘towcars’ even if they’re 4x4s.
The triangle made of metal at the front of the trailer. This is the most visible part of the chassis.
The backbone, or skeleton of the caravan on which everything else is built.
Roads are never perfectly smooth or flat. You need suspension to absorb the undulations and provide a smooth ride. The two main parts are the spring, which carries the load, and the shocks (dampers), which smooth out or dampen the bouncing from the springs as the vehicle moves along the road.
Wheels and tyres
Pretty straightforward, similar to what’s on the car, but there are differences which we’ll cover later.
There are so many terms; GCM, GVM, TBM, ATM and more. This is a big, complex subject so we’ll cover it in a specialised article. For the moment just know this – there are lots of complex weight limits to comply with.
This is a little plaque on the trailer, somewhere on the drawbar (see, using the lingo already) or maybe in a box close by the drawbar. It has on it some of the weights referred to above.
Vehicle Identification Number. A number unique to a vehicle, be that trailer or towcar, and can be found on the trailer placard.
The retractable or detachable wheel used to support the drawbar when the trailer is not hitched. Sometimes it’s just a plate, sometimes it’s an actual wheel.
Never trust a trailer park brake! Always chock your wheels before you unhitch.
This is the bit of metal on the towcar which houses the receiver for the hitch. Pictured below is a towbar with a selection of hitches, and a 4×4 recovery point in the receiver. Generally, we use a 50mm square receiver so we can choose the most appropriate hitch for the job.
The ball, 50mm diameter, used on a standard hitch as pictured below. This works for trailers of 3,500kg or below. For trailers above 3,500kg you need something heavier-duty, for example a 70mm ball.
Used on lifted 4x4s to lower the ball to the appropriate height for the trailer.
There are several types designed for offroad use so the trailer can rotate relative to the towcar, beyond the point possible with a 50mm hitch.
Hitch pin and clip
Goes through the receiver and hitch to secure it. Some are lockable to deter theft. It’s always a good idea to carry a spare as if you lose one…you’ve got problems.
If the trailer disconnects from the towcar by accident, then it’ll separate and the breakaway controller wire will stretch tight, pull out the controller and apply the trailer brakes. This system is mandatory on trailers over 2,000kg GTM (weight on trailer axles).
If the hitch fails, the trailer may separate from the towcar. This is prevented by safety chains. All trailers need at least one and trailers over 2,000kg GTM (weight on the axles) must have two.
Safety chain connectors
What connects the safety chains to the towcar. A recently popular option is yellow rated hooks which are designed for lifting but also send caravan park happy hours into meltdown for reasons teams of highly qualified psychologists have yet to determine. Read more here.
Trailer electrics (Round, 7, 12-pin)
Any trailer requires electricity to operate its brakelights, indicators and if fitted, electric brakes. This electricity is provided by the ‘trailer electrics’. You plug the trailer into the towcar. Unfortunately, there are round plugs, and flat plugs, and the flat is either 7 or 12 pin, and this makes connecting any trailer to any towcar something of a “will it connect” lottery. You can get adaptors from round to flat. More on this later.
Brake controller, electric brake controller
Trailers over 2,000kg GTM (gross trailer mass, weight on the trailer axles) must have independent brakes, and that’s usually electric brakes. Independent brakes mean the driver can operate the trailer brakes without touching the towcar brakes in case of emergency, although normally, the trailer brakes are set to operate in concert with the towcar brakes. To do that you need a brake controller, and a couple are pictured below.
These aren’t necessary for trailer towing but provide power from towcar to trailer for the purposes of charging the trailer battery used for living (light, coffee machines etc) from the towcar. You don’t typically see Anderson plugs on anything but travel trailers.
All but the smallest trailers have (should have) parkbrakes, but they’re often pretty ineffective. Chocks are more reliable.
If the trailer is wider than the towcar you need towing mirrors so your rear vision is not impaired. These may be add-ons or replacements.
WDH – weight distribution hitch
Not something you often see, but this is an additional device which distributes the weight of the trailer’s hitch on the car to the front wheels of the towcar and the wheels of the trailer. Only use if specifically recommended, there’s pros and cons, and not all vehicles are compatible.
Single axle, dual axle, tandem axle
Whether the trailer has two wheels (single axle) or four wheels (tandem, dual axle). Some trailers may have three axles, but those are rare.
When the trailer swerves from side to side behind the towcar. This often leads to a crash. The best way to fix sway is to apply the trailer brakes but NOT the towcar brakes; see brake controller above.
Trailer Stability Control, two types, fitted to either the trailer or the towcar, both designed to combat sway. Both use sensors to detect the start of sway – the trailer version applies the trailer brakes, the car version applies the car brakes. You can read more about that here.
Where the trailer connects to the towcar, which will be a ute or a truck, by means of a hitch on the bed of the towcar. The design offers much better towing stability (less chance of sway) and greater living space for a given trailer length, but you need a truck or a ute and lose a lot of space in the towcar. They are also not suitable for offroading.
Trailers can be stolen, but you can deter thieves. Here’s an example of a trailer lock. If you ever ask about anti-theft advice on a van forum, you will be told by multiple people, “if they really want it, they’ll take it”, which you already knew of course.
That’s the glossary done – if there’s a term we’ve missed that you’re unsure about, ask in the comments!