Car towing a trailer
Safety

Towing Essentials: What You Must Know Before Hitting The Road

So, you want to tow a boat or caravan, or sling a trailer behind your car. It sounds simple – hook it up to the tow bar, drive off into the sunset – but the reality is more complicated.

By Shell on Aug. 11, 2020

Get it wrong and you can end up in some scary and even life-threatening outcomes, as illustrated by dash-cam footage the world over.

How do you ensure you’re properly prepared and doing it safely? Here are some things you need to know.

The numbers game

Without knowing some key figures and doing the sums, you’re essentially flying (or towing) in the dark.

First, you need to establish your car’s maximum towing capacity – look in your owner’s manual. There will be different numbers for ‘braked’ and ‘unbraked’ trailers, so make sure you pick the right one.

Second, you need to know the weight you’re towing. If it’s a caravan or trailer, remember you won’t be towing it at its tare (unladen) weight, so factor in the necessary extra kilos.

Ideally, your car’s maximum capacity should exceed the towing weight by about 20 per cent. If your car has a 3,500kg rating, for example, you really don’t want to be towing much more than 2,800kg. Why 20 per cent? Because towing ratings are maximums and a safety margin is recommended.

But wait …

You also need to ensure your car’s maximum tow ball download (TBD) is sufficient. This relates to the force pushed onto the tow ball, which is about 10 per cent of the weight being towed. Most cars will have a TBD rating that adheres to this rule (350kg TBD, 3,500kg maximum capacity) but in some it can be proportionally smaller, limiting what you can tow.

Have a think, too, about whether you’ll be loading up your car. If so, you need to know your car’s maximum gross vehicle mass (GVM) and gross combination vehicle mass (GCVM) numbers. The former is the maximum allowed weight for your vehicle, the latter is the maximum allowed weight for your vehicle and a trailer.

Double-checking these numbers is vital because a maxed-out GVM often dictates a reduced maximum towing capacity and a fully loaded vehicle and trailer can easily exceed the GCVM.

Here’s a handy diagram to help keep all those numbers and acronyms straight:

Towing Terms Explained

Press the marked areas to learn more about each
Towing vehicle infographic
Detail 1

Maximum Towing Capacity (braked/unbraked) = How much can your car tow?

Detail 2

Gross Vehicle Mass (GVM) - kerb weight = payload = How much can I carry?

Detail 3

Towball Download = Typically 10% of ATM (see 4)

Detail 4

Agreggate Trailer Mass (ATM) = How much am I towing?

Detail 5

ATM = GRV = Gross combination vehicle mass  = How much can I carry and tow?

Press the marked areas to learn more about each

Staying smooth

Towing plays havoc with your car’s intrinsic handling and its other dynamic characteristics – it won’t accelerate or stop as quickly or corner as effectively, and it will be infinitely harder to reverse. At highway speeds, the trailer itself could start to fishtail in an ever-worsening, eventually uncontrollable manner (something called ‘trailer sway’).

Safe towing, then, is all about not upsetting your car-and-trailer’s fragile dynamic balance. That means looking up, anticipating what’s around you, staying well back from traffic and being super-smooth with all accelerator, braking and steering inputs.

If you haven’t towed before, start with shorter trips on familiar roads before progressing to longer journeys. Even better, get some expert guidance from a driver-training organisation.

Choosing the right vehicle

If you’re intending to buy a tow vehicle, some are naturally better than others. The laws of physics give bigger, heavier cars an inherent advantage and they typically have higher ratings, too.

Rear-wheel-drive cars are also great because the towing weight is distributed over the driving wheels, aiding traction. Cars that drive all wheels are even better. Front-wheel-drives are less desirable because towing unloads their driving wheels, reducing traction. On a steep, slippery surface – perhaps a boat ramp – that can be a problem.

Diesels, meanwhile, have an advantage over petrols because they produce their power at lower revs range and use less fuel.

None of which is to say you can’t tow with a front-wheel drive petrol vehicle – they’re just better suited to lighter-duty roles and have their limitations.

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Disclaimer

Viva Energy Australia Pty Ltd (“Viva Energy”) has compiled the above article for your general information and to use as a general reference. Whilst all reasonable care has been taken by Viva Energy in compiling this article, Viva Energy does not warrant or represent that the information in the article is free from errors or omissions or is suitable for your intended use.

Where information, recommendations, opinions or ideas have been sourced from third parties external to Viva Energy (Third Party Information), Viva Energy cannot be certain that the Third Party Information is accurate, current or complete, nor should a mention of any business, product, service or website of a third party be taken as a recommendation, approval or endorsement of, or warranty or claim regarding, that business, product, service or website.