How to increase towing capacity: A guide to towing upgrades

As we Australians take our fun more and more seriously, the idea of towing a caravan or boat behind our vehicles is an increasingly common one.

This is (partly) what’s been driving the move to dual-cab utes as our big-selling cars of choice, as well as the increasing towing abilities of those cars.

In the case of every new car and commercial vehicle for sale in Australia, the government dictates that it is rated for a maximum towing limit.

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That’s to ensure the vehicle remains safe to drive with a load attached, as well as hopefully ensuring the towed load won’t do any damage to the tow-vehicle.

In the real world, it’s a lot more complicated than that, but it remains that towing more than your car is rated for is a sure way to wind up in legal trouble and, if the worst happens, an insurance swamp as well.

So what is towing capacity in the first place? Towing ratings generally come in two forms: The unbraked trailer and the braked trailer.

In the case of the former (and as the name suggests) the trailer does not have brakes of its own. For that reason, it relies on the brakes of the towing vehicle and, therefore, must be kept as light as possible.

The braked-trailer limit, meanwhile, applies to trailers with their own electric or mechanical brakes that can contribute to the combination’s total braking force. With its own brakes, such a trailer can afford to be heavier.

Either way, though, it’s illegal to haul a trailer and load of greater mass than the legal limit for a particular make and model.

And get used to these terms: GVM, the total mass of the vehicle and everything in it (including the tow ball weight) and; GCM the total mass of the vehicle and trailer combination and everything in it/on it.

Clearly, how much can I tow, is a very complex question. And, the info won’t be found on a compliance plate on the vehicle, either, you’ll need to look in the owner’s handbook for the details.

It’s illegal to haul a trailer and load of greater mass than the legal limit for a particular make and model. (Image: Sam Rawlings)

But what if you need to tow more than that legal limit?

Well, you could simply go out and buy a bigger, heavier vehicle with a higher towing rating. But what if you’ve already tipped plenty of time and money into making your current vehicle otherwise perfect for your tasks and lifestyle? Surely, an upgrade of that vehicle to tow a bigger load makes some sense.

And that’s where the aftermarket comes in. As caravans, boats and worksite equipment gets bigger and heavier, more and more owners are turning to a towing upgrade to achieve their ends.

The first thing to know is that the increasingly popular GVM upgrade is not the same as a towing limit upgrade. In fact, a GVM upgrade concerns only the payload of the vehicle and, if you then use that extra payload while the GCM remains the same, you might, ironically, have a reduced towing limit.

So, does a GVM increase impact towing capacity at all? Not in a legal, upper limit sense, but such an upgrade is a way to increase towing performance and safety, if not actual capacity.

Add a GVM upgrade to your, say, Ford Ranger, and it’ll still be legal to tow the same 3500kg, but it will do it more easily and more safely.

As caravans, boats and worksite equipment gets bigger and heavier, more and more owners are turning to a towing upgrade to achieve their ends. (Image: Sam Rawlings)

GVM upgrades vary from vehicle to vehicle but often include components such as stiffer springs, revised bushes, stronger hitches, better dampers and wheel alignment adjustments.

But even then, you might find you need bigger brakes, different tyres and even revised axles or wheel bearings to make the jump to a higher GVM.

It all depends on the vehicle in question and there’s no one-size-fits-all GVM upgrade, so you need to have a specialist tackle your vehicle on a one-on-one basis with regard to how it’ll be loaded and how you plan to use it. The pros have a range of kits ready to suit popular fitments.

The other thing to know is that you won’t be making 1000kg jumps in a GVM upgrade. Between about 300kg and 600kg is the gain you’ll make, but that’s a big enough difference for some to make the investment.

But what about GCM upgrades? This is where it all gets a bit murky, because some specialists will tell you that since there’s no standardised test for a GCM upgrade, it can’t be done with any degree of certification.

Other mobs will tell you they have GCM kits to upgrade a limited number of vehicles (typically the Toyota Land Cruiser and Prado stablemates) and that these can legally upgrade towing capacity.

You might find you need bigger brakes, different tyres and even revised axles or wheel bearings to make the jump to a higher GVM.

Because there’s no hard-and-fast government stance on this subject, the best we can do is give you what seems to be the current status quo on the matter:

NSW, SA and Victoria will recognise a revised GCM if the vehicle has been independently inspected by a consulting engineer and usually the state’s own authorities.

Tasmania allows a revised GCM if the kit has been previously certified by the manufacturer and professionally installed.

Queensland no longer recognises a revised GCM above the GCM nominated by the vehicle’s manufacturer. That said, Queensland is said to be looking into this situation.

WA, ACT and NT, meanwhile, do not allow a revised GCM above the manufacturer’s GCM if the vehicle is modified anytime after it’s been registered.

Having said that, at least one major local suspension manufacturer we contacted insisted that “There is currently no process via a government body that will allow an increase of a vehicle’s GCM in Australia”.

Brand-new vehicles that undergo the upgrade prior to registration can be certified as safe and legal by the upgrade supplier. (Image: Brendan Batty)

If you could legally increase your GCM, you’d theoretically also increase your towing capacity, again, provided you don’t gobble up the extra capacity by loading more into the tow-vehicle.

But remember, that’s theoretically, not – as far as the law is concerned – practically.

In the case of GVM upgrades, brand-new vehicles that undergo the upgrade prior to registration can be certified as safe and legal by the upgrade supplier.

If you’re converting an existing car, you may – depending on state or territory – need to have an independent engineer sign off on the deal. The good conversion companies can usually put you in touch with these engineers.

But don’t be put off by that requirement, as suspension upgrades for towing have been carried out for decades, so it’s familiar stuff for the right engineer.

Again, a GVM won’t legally increase your towing capacity, but it can make a vehicle much better and safer at towing that same loads as an unmodified one.

It’s far better to go to a specialist who has engineered a GVM solution rather than try to mix and match bits and pieces using guesswork. (Image: Track Trailer)

And GCM upgrades? You might want to make life simple for yourself and simply buy a bigger, heavier vehicle with a higher towing limit as standard. Many dual-cab ute, SUV and car owners are switching to a light truck for this reason.

Even if you do just wish to improve your vehicle’s towing ability and safety (without a towing-limit increase) with a GVM upgrade, there can be traps. It’s far better to go to a specialist who has engineered a GVM solution rather than try to mix and match bits and pieces using guesswork.

Air-bag helper-springs, for example, can be used quite effectively on some vehicles, but others (typically some dual-cab utes with leaf rear springs) can suffer catastrophic chassis failure through the use of air-bags.

The same goes for changing spring rates. By mis-matching the front and rear suspension of a vehicle, you can easily wind up with a vehicle that is less capable and less safe as a tow-vehicle. This is not a project for the DIYer.