What can my car tow?

What can your car tow? The short answer is the lowest of several limits, and the towing capacity in the brochure is only one of them. The vehicle and the towbar each have a rating, and so do the trailer and its tyres. The combined weight of car and van has a ceiling of its own as well. This guide explains each figure and where to find it, then how to check the numbers with real weights before you buy a van.

We are a classifieds site, not a towing engineer, and nothing here is legal advice. The figures that bind you are on your vehicle's plate and in its handbook. Your towbar and the trailer carry their own.

The figures you need from your vehicle

The Western Australian Department of Transport's towing guide says that before buying a trailer or caravan you should consider your vehicle's towing rating, GVM, GCM, axle capacities and tow hitch download rating, all of which are in the vehicle manufacturer's handbook (Department of Transport WA). It defines them this way ¹:

• Towing capacity: the trailer weight the vehicle maker allows, which comes with a towball weight limit; neither may be exceeded.
• GVM (gross vehicle mass): the most your vehicle may weigh fully laden.
• GCM (gross combination mass): the most the vehicle and trailer may weigh together, which the guide notes can be less than the GVM plus the towing capacity.
• Axle capacity: the most each axle may carry, front and rear.
• Tow hitch download: the weight the trailer puts on the tow ball.

A handbook can give two towing figures: one for a trailer with its own brakes and a lower one for a trailer without brakes. The WA guide caps the unbraked figure at the lesser of the vehicle maker's rating or 750 kg ¹.

The lowest limit wins

NSW sets the rule plainly: the loaded mass of the trailer must not exceed the lowest of the towbar or coupling rating, the vehicle's maximum towing capacity, the trailer's maximum carrying capacity and the tyres' maximum carrying capacity (NSW Government).

When the vehicle maker gives no towing figure, NSW sets a default. With working brakes on the trailer, the limit is one and a half times the unladen mass of the towing vehicle; when the trailer needs no brakes, it is the vehicle's unladen mass ².

The towbar has its own rating

A towbar can be rated lower than the vehicle, and then the towbar's rating is the limit under the NSW rule above ². The WA guide makes the same point from the other side: when the towbar fitted exceeds the capacity the vehicle maker approved, the lesser of the two values is the towing capacity ¹. It also says towbars and couplings made after 1 July 1988 must clearly and permanently display their maximum rated load, unless they are a permanent part of the vehicle ¹. Look for that plate before you trust a second-hand towbar.

The ball matters too. The common 50 mm tow balls are not rated beyond 3,500 kg, and a trailer between 3,500 kg and 4,500 kg needs a 75 mm ball or another coupling rated to its ATM ¹. On a towbar with a tongue that can be turned upside down, the rating can change in the other position, and a plaque should show it ¹.

GCM: the limit most people miss

The GCM caps the whole rig. The WA guide works an example with a vehicle that has a 2,740 kg GVM, a 4,600 kg GCM and a maximum trailer weight of 2,250 kg ¹:

• With the trailer loaded to its maximum of 2,250 kg, the vehicle can weigh at most 2,350 kg, well under its GVM ¹.
• With the vehicle loaded to its 2,740 kg GVM, the trailer can weigh at most 1,860 kg, well under its towing capacity ¹.
• With both loaded to their maximums, the rig weighs 4,990 kg and is over its GCM ¹.

So a fully loaded car eats into what you can tow. Count the people, the fuel, the fridge in the tray and the bikes on the roof before you decide how heavy a van you can pull.

Towball download

The trailer's weight on the tow ball counts towards your vehicle's load. The WA guide says the tow hitch download must be included in the tow vehicle's GVM, and must not exceed the maximum for the vehicle or the towbar ¹. That is why a heavy ball weight can push a loaded dual cab over its GVM even when the van is under the towing capacity.

How much download is right? NSW suggests that about 5 to 10 per cent of the total mass of the trailer and its load should be carried by the vehicle through the coupling, with about 60 per cent of the load forward of the axle centre ². The WA guide gives 8 to 10 per cent of the ATM as a guide, up to the towbar's limit, and warns that both too much and too little download make the combination less stable ¹. Some European-designed vans need less, so follow the van maker's figure where it gives one ¹.

The trailer's side of the sum

On the trailer, the figure to compare with your towing capacity is the ATM, the most it may weigh when fully loaded. The WA guide defines the ATM as the GTM plus the tow hitch download, and the payload as the ATM minus the tare ¹. A van's tare is its weight empty, so a brochure tare tells you little until you know the ATM as well.

Heavier trailers bring more equipment rules. In NSW a trailer up to 750 kg GTM needs no brakes, one from 751 to 2,000 kg needs brakes on both wheels of at least one axle, and one from 2,001 to 4,500 kg needs brakes on all wheels ². Over 2 tonnes GTM a trailer also needs an automatic breakaway system, and the brakes must be operable from the driver's seat ². A trailer under 2,500 kg loaded needs at least one safety chain, and a heavier one needs two ².

Licence, speed and mirrors

Your licence decides whether you can tow at all. In NSW, learner drivers may not tow, and P1 drivers may only tow a small trailer with up to 250 kg of unloaded weight ². A car licence in NSW covers vehicles up to 4.5 tonnes GVM, so a heavier tow vehicle needs the matching rigid licence class ³.

Speed limits change with weight in some places. In NSW a vehicle towing a single trailer must not exceed 100 km/h, whatever the posted limit, when the vehicle's GVM or the combination's GCM is over 4.5 tonnes ². The WA guide says a vehicle towing a trailer in Western Australia cannot exceed the lesser of the posted limit or 100 km/h ¹.

The NSW page also says extra mirrors may be needed when towing a large trailer, and that a vehicle with an automatic transmission may need an extra transmission oil cooler ². Ask about both when you have a towbar fitted.

Check it with real weights

Brochure weights are only a starting point. Every option fitted to a van and every item you pack comes out of the payload. The WA guide says vehicle and trailer weights can be measured at a public weighbridge, and the download can be found by weighing the trailer at its coupling ¹. Weigh the car on its own, the van on its own and the two together, loaded the way you travel, then compare each figure with its limit.

Our caravan buying guides include one on lightweight caravans, which explains what you gain by keeping the van light. Many of the lighter vans are listed under camper trailers and pop top caravans.

Using our tow-match tool

Our tow-match tool takes two numbers from your vehicle's handbook: its braked towing capacity and its towball download limit. It opens a search of the towables on Caravan Domain whose ATM is within that capacity and, when you give the ball limit, whose ball weight is within it too. Enter the WA guide's example vehicle, with its maximum trailer weight of 2,250 kg, and the tool opens a search of the towables with an ATM of 2,250 kg or less ¹.

The tool compares the van's ATM with your towing capacity, which is the comparison the rules start from. It does not know your GCM or what you carry in the car, so treat the results as a shortlist. Signed-in buyers can save a tow profile, and ads that fit it carry a "Within your tow rating" badge.