How to drive with a trailer

Knowing how to tow a trailer confidently and safely is a vital skill for any driver, from a single-axle box-trailer or camper-trailer to motorcycle and jet-ski trailers to heavy duty multi-axle caravans, horse floats and car/boat trailers.

However, achieving proficiency requires a blend of experience and knowledge. While driving experience can only be accrued over time, we can certainly provide an overview of the knowledge required with our trailer towing guide.

Licence requirements

Each state or territory has its own rules in regards to licence requirements for towing, so your first step should be contacting your local transport authority to find out if any specifics apply to you.

As a general rule, anyone with a full car licence can drive a vehicle that does not exceed 4.5 tonnes Gross Vehicle Mass (see next section) and can tow a trailer weight up to the maximum specified by the tow vehicle’s manufacturer.

Different towing rules and trailer weight restrictions apply to provisional licence holders (red plate P1 and green plate P2) and even learner drivers are allowed to tow in some states or territories. So, it’s important to always check this before you tow.

Towing terms and acronyms 

ATM? GCM? TBD? These can often be found on your tow vehicle’s and trailer’s compliance plates, in owner’s manuals and many articles and discussions about towing, but what do they actually mean?

Tare Mass or Weight 

This is the weight of an empty standard vehicle with all of its fluids (oils, coolants) but with only 10 litres of fuel in the tank. We assume 10 litres was chosen as an industry standard to allow otherwise empty vehicles to be driven to and from a weighbridge.

Kerb Mass or Weight

This is the same as Tare Mass, but with a full tank of fuel and any accessories fitted (bull bars, tow bars, roof racks etc). Think of it as your vehicle literally parked at the ‘kerb’ and ready for you to get in and drive away.

Gross Vehicle Mass (GVM) or Weight (GVW) 

This is the maximum your vehicle can weigh when fully loaded as specified by the manufacturer. You will usually find this GVM figure on the vehicle’s weight placard (generally found in the driver’s door opening) or in the owner’s manual. So GVM is the Kerb Mass plus driver, passengers, luggage and whatever else you’re taking with you. And if you’re towing something, GVM also includes the Tow Ball Download (see separate heading).

Tare Trailer Mass or Weight (TARE)

This is the weight of an empty trailer. The term ‘trailer’ covers everything you can tow or ‘trail’ behind a vehicle. If it’s a camper trailer or caravan, its Tare Mass 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)

This 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. The GTM is usually displayed on the trailer or in the owner’s manual.

Aggregate Trailer Mass (ATM) or Weight (ATW)

This is the Gross Trailer Mass (GTM) plus the Tow Bar Download. 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) 

This is the maximum weight allowed for your vehicle and trailer combined, as specified by the tow vehicle’s manufacturer. This is where you have to pay close attention to your vehicle’s GVM and your trailer’s ATM, because those two figures determine the GCM and one directly affects the other.

Tow Ball Download (TBD)

The amount of weight on your tow bar is crucial to safe and efficient towing. Any quality tow bar will have a placard displaying the maximum tow bar capacity (kg) and maximum tow bar download (kg). Make sure the tow bar you choose is designed specifically to suit your vehicle and your towing capacity requirements.

Tow vehicle requirements

The first thing to ensure is that the loaded weight of the trailer you’re planning to tow does not exceed the legal towing limit of your vehicle, its tow bar and maximum tow-ball download. Electronic trailer sway control in the tow vehicle’s stability menu is also desirable for obvious reasons, along with a reversing camera which makes light work of accurately lining up your tow-ball and hitch when hooking up a trailer.

There’s plenty of chest-beating about big towing capacities in vehicle advertising, but the figure you really need to focus on is the GCM, or how much you can legally carry and tow at the same time. You might be shocked to discover that you need to reduce your tow vehicle’s payload by up to 500kg or more to stay below the GCM limit.

Make sure your towing mirrors are up to the job. If towing a small box-trailer or camper-trailer, the standard door mirrors might be adequate. However, if towing a taller, wider and heavier trailer,  towing mirrors are a legal and practical necessity, as clear eye-lines down both sides are essential. Also ensure that your tow vehicle’s cold tyre pressures are correct for towing as displayed on its tyre placard.

And if your trailer is equipped with an electronically controlled braking system, ensure that the trailer’s and tow vehicle’s electrical plugs are compatible and brakes correctly adjusted. To do that, start off with the cabin-mounted controller on or just below its middle setting and then, with a few gentle brake applications at low speed on a quiet street, gradually increase the caravan’s braking force until you feel its brakes biting a fraction harder than the tow vehicle’s. This can feel like the trailer is ‘tugging’ against the tow-ball. From there, slightly decrease the setting to establish a nice balance between them and once under way continue fine tuning as needed.

Trailer requirements 

Trailers come in all weights, shapes and sizes from the smallest box-trailer to the largest multi-axle caravan, but they all require the same check-list (particularly if you’re renting a trailer) to ensure safe and enjoyable towing performance.

It must be registered (if required), its chassis and towing hitch should be free of structural damage and all lights, brakes (some trailers use self-activated mechanical brakes), axles, wheel bearings, wheels and tyres should be in good working order.

Trailers weighing up to 750kg do not require brakes but those weighing 751-2000kg must have braking on at least one axle. Trailers from 2001-4500kg require brakes on all axles, plus an automatic breakaway system that applies the brakes if the trailer separates from the tow vehicle.

Trailers weighing up to 2500kg must also be fitted with at least one safety chain to stop the trailer’s drawbar hitting the road if the coupling disconnects and two chains are required for trailers greater than 2500kg.

Also ensure that the tow-ball is the correct size for the job, as they vary in diameter depending on load requirements. Also ensure it has been tightened to the recommended torque setting.  The trailer’s towing hitch should lower easily onto the tow-ball and allow the hitch’s locking mechanism to fully engage with the neck of the ball.

For heavy trailers, a weight distribution hitch (WDH) is a wonderful device which does exactly what its name implies. Its powerful leveraging effect provides a better distribution of weight across all axles resulting in a level ride height for tow vehicle and trailer, which is particularly important in maintaining effective steering and front-wheel braking in the tow vehicle.

Carry as much of your trailer’s load on, or as close to, its axle line as you can with no more than 60 per cent of its loaded weight ahead of the axle line. Too much weight behind the axle line can create a pendulum effect that can generate dangerous trailer sway (see separate heading). And get the load as low as you can, to lower the centre of gravity for greater all-round stability.  

Learning to tow

Learning to drive with a trailer should be no different to how you learned to drive a car. Your vehicle behaves differently with a trailer behind it and those differences increase with the size and weight of the trailer.

For example, you may not notice much difference with a small box-trailer behind you. However, with a large multi-axle caravan, horse float or car/boat trailer weighing several tonnes, you’ll notice big changes.

Acceleration will be much slower, braking distances will be much longer and handling will be ponderous. Climbing and descending hills will require the use of lower gears, regardless of manual or automatic transmissions, to assist the engine’s pulling performance on the way up and its engine-braking on the way down to reduce load on the braking system.

You’ll also have to allow for much longer distances when overtaking and more room when turning corners, using wider arcs to ensure the trailer’s wheels don’t clip inside kerbs on the way through. Rear vision through your central mirror will usually be blocked and you’ll have to rely entirely on your door mirrors.

So, there’s a lot to learn. And, like learning to drive, excessive speed is your greatest enemy during this process. A tow vehicle and its trailer are inherently unstable at speed and have a lot of inertia behind them. If you need to suddenly swerve or there’s a corner approaching, this combination is not too keen on slowing down or changing direction.

So, it stands to reason that the faster you drive, the greater the risk of losing control. So, slow is the go when learning to tow, with speeds increasing as your experience and confidence increase.

Even so, from our experience, it’s a good idea to drive slightly below any posted speed limit regardless of your experience level, to provide an extra safety margin should you need to react quickly. And you should always check if your vehicle’s owner’s manual has recommended towing speeds (some do).

White knuckle fever: reversing and trailer sway

Two tasks that can cause drivers new to towing to tightly grip their steering wheels and suffer cold sweats are reversing and trailer sway, but both can be safely managed with experience and a calm, confident approach.

Reversing a trailer requires learning the basics and the best place to do that is a wide, open space like an empty car park where you can practice with minimal risk of running into anything. Having someone observe and guide from outside is also advisable, not only when learning but always when reversing large trailers.

Small trailers can often be reversed by simply looking over your left shoulder through the tow vehicle’s back window. However, with large trailers that completely block that view, you must learn how to reverse using only your door-mounted towing mirrors. With a bit of practice this is surprisingly easy to learn and will become second nature, as it is for professional semi-trailer drivers who do this every day.

When reversing, if you want the rear of the trailer to turn left, turn the steering wheel to the right. And if you want the rear of the trailer to turn right, turn the steering wheel to the left. While this may seem counter-intuitive at first, just keep reversing the trailer from left to right to left to right using your mirrors for as long as it takes to master this ‘jack knife’ technique.

Then as your experience and confidence grows, set up some plastic markers to create spaces to reverse your trailer into, starting wide and getting narrower as you master each stage. After sufficient practice using these techniques, you’ll be able to reverse your trailer calmly and accurately in any situation.

Trailer sway on the highway is an unnerving and potentially dangerous experience that every driver wants to avoid, but it can happen for a variety of reasons (sudden wind gusts, poor weight distribution, excessive speed etc) and you need to be prepared to deal with it calmly and effectively.

In any case, we can’t agree with the old adage that you should accelerate to eliminate trailer sway, because we’re yet to see any electronic trailer sway control program that accelerates a trailer out of trouble! Fact is, the higher the speeds, the more unstable the whole rig becomes.

From our experience, you need to very gently ease off the accelerator to avoid any sudden forward weight transfer and then gradually start applying enough brake pedal pressure (with properly adjusted trailer brakes of course) to slowly bring it all under control. Once your pulse rate returns to normal, you should also determine what caused the sway in the first place to avoid it happening again.

Fortunately, many utes and SUVs these days are armed with trailer sway control in their electronic stability menus, that are very efficient at stopping trailer sway before it starts. And mechanical trailer sway control devices can also be fitted to your trailer’s WDH.