Mobility

Towing 101: what to know before you tow

A car towing a caravan along dusty red dirt road in the outback

Toby Hagon

Posted January 28, 2022

Everything from tow balls, torque, trailers, tyres and how to drive when towing - there’s a lot more to know about towing that you need to know before you hit the road.

While being able to tow a trailer, caravan, or boat is one of the greatest conveniences a car can offer you, the consequences can be deadly if you don’t know what you’re doing.

The dangers of navigating a service station forecourt or a fast-food carpark is nothing in comparison to the dangers of a poorly-connected caravan or trailer while travelling 100km/h down the freeway.

Here is everything you need to consider before, during, and after you connect a caravan, boat or trailer to your tow vehicle.

Consider what’s doing the towing

Forget power, it’s torque that does all the work when you’re towing.

That’s why so many people turn to diesel engines for towing caravans and trailers. Modern turbo diesels can produce plenty of grunt without needing to rev too hard - making them ideal for hauling heavy loads.

If you’re looking to tow very heavy loads over big distances it’s worth considering something with a bit more grunt. Check out the specifications and make sure you’ve got at least 400Nm of torque; anything approaching 500Nm is even better. More than that is a bonus and will make much lighter work of towing.

Check out our article on the best cars for towing a caravan for specifics on what cars to consider.

A Toyota Prado towing a caravan on a dirt road

Towing is a complex issue for caravan, boat and horse-float owners. Image: Supplied.

Understand the towing jargon

There’s an assortment of jargon, acronyms and numbers associated with towing.

The most obvious is the ‘maximum tow capacity’, which is what a car can legally – and safely – tow. Exceeding that tow limit not only risks a fine, but could also damage the vehicle or contribute to a crash.

Then there’s the ‘down weight’ or ‘tow ball download’, which is the maximum weight that can be pushing down on the tow ball when the car is parked on a level surface. Most of the time you want about 10 per cent of the weight of the trailer pushing down on the hitch; there are scales for measuring it.

The ‘gross vehicle mass’ (GVM) is how much weight the car can take, including the weight of the car and whatever you pack into it, including people, luggage, and fuel.

When calculating the GVM for towing, you need to take into account how much downward weight the trailer is exerting on the rear of the car. If you have 350kg pushing down on the tow hitch, then you have to take 350kg off the payload of the car.

Next comes the ‘gross combination mass’ (GCM), which is the weight of the car and the trailer and everything in each of them.

Dig deeper than the maximum tow capacity

Just because an SUV or ute says it can tow 3.5 tonnes doesn’t mean it can – at least if you want to take the family and all your gear with you.

Once you take into account all those other limits, some tow vehicles will only let you carry a few hundred kilograms, possibly less. While you also have to consider things such as the maximum axle load – ensuring you’re not overloading one end of the car – it’s also crucial to calculate GCM and GVM for your towing setup; either one can limit your payload.

 

Isuzu D-Max towing a caravan in regional Australia

Torque counts when towing large caravans. Image: Supplied.

Crunching the numbers when it comes to towing

The Toyota Prado gets a huge 150-litre fuel tank so is great for towing without having to stop every few hundred kilometres to refuel.

But if you want the leather-clad Kakadu model you can only put 340kg in the car once you’re towing the maximum 3000kg it’s rated for. That’s 340kg in total for people, luggage, camping gear, food and water.

The just released Toyota LandCruiser 300 Series has a tow capacity to 3500kg. But the vehicle itself weighs up to 2630kg and with a gross vehicle mass limit of 3280kg it means you can only carry 300kg of people and gear when towing that max amount (accounting for the 350kg pushing down on the tow ball).

Impressed by the 4500kg tow limit of the brash new Chevrolet Silverado ute? Don’t get too excited. If you are utilising the maximum tow capacity of the vehicle, the payload drops to a mere 117kg; we doubt there would be many couples that have a combined weight below that - and that’s before they throw in luggage.

Consider a car with a higher towing limit than you’re ever likely to use, so it doesn’t constrain you in other areas.

Braking when towing a caravan or trailer

Anything over 750kg requires the trailer to have its own braking system, both to adhere to the law and to reduce the strain being put on the braking system of the tow vehicle.

Up to 2000kg you can have mechanical brakes, which activate a piston or cable when the trailer pushes against the car.

Over 2000kg you need electronic trailer brakes, which can ‘talk’ to a brake controller in the car.

You can adjust the brake bias – or how aggressively the trailer brakes compared with the car – and independently apply the trailer brakes to control trailer sway.

 

An isuzu mu-x ls-t towing a caravan

If you are towing over two tonnes, electronic brakes are a must. Image: Supplied.

Fuel consumption when towing

Vehicles powered by diesel and petrol are best suited to towing in Australia. There are many of these vehicles with tow capacities of 3.5 tonnes. However, be aware that the car will be slower and use a lot more fuel when towing. Blame physics. You may find that your fuel consumption doubles when towing.

It’ll also take longer to stop and behave differently over bumps, so drive accordingly.

And best to get used to tow vehicle and your rig before joining the holiday rush. At the very least, practice reversing with a trailer before hitting the Maccas carpark. It could save some red faces.

 

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