Do you really need a GVM upgrade?

A vehicle’s GVM, or Gross Vehicle Mass, is the amount of weight you can carry combined with the total mass of the vehicle (known as kerb weight).

If you have a kerb weight of 2500kg and a payload of 650kg, the Gross Vehicle Mass is 3150kg. That means you can add or carry 650kg of accessories or passengers, before you're over GVM.

While 650kg sounds reasonable, that can be eaten up quickly with bar-work, winches, drawers and long-range fuel tanks, hence why GVM upgrades are so popular with four-wheel drivers, as you are legally permitted to carry more weight with an increased GVM over the factory offering.

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What is a GVM upgrade?

A GVM upgrade involves the professional fitment of an aftermarket suspension kit which has been designed, tested and approved in Australia to increase the factory GVM, allowing you to carry more weight legally.

Commonly, this means replacing the factory springs, shock absorbers and stock suspension components at a minimum; brake and tyre upgrades might also be required or even entire replacement axle upgrades.

This is different to fitting just an aftermarket suspension kit, even though most GVM upgrades will also increase the ride height of a vehicle from factory, as well as provide a higher payload capacity figure.

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Why would you need a GVM upgrade?

If you are carrying payload figures close to the factory GVM constantly or regularly, you are the perfect candidate for a GVM upgrade. If you exceed the factory payload figure provided by your vehicle’s manufacturer, your 4WD is now considered to be in an unroadworthy condition.

Police have been targeting and weighing overloaded 4WDs and trailers, especially in recent times, so there is a very real risk you will be caught. If your vehicle exceeds the factory GVM figure, this will also void your insurance in the event of an accident. It’s not worth the risk at all; you’ll either need to put your vehicle on a serious diet, or spend the cash on a GVM upgrade.

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Pre-registration GVM upgrades

If you have just signed on the dotted line for a new 4WD, there’s an option to have the factory GVM upgraded before registering it for the first time. Detailed and expensive testing is carried out by authorised suspension manufacturers during development, and once relevant tests are passed these upgrades are granted by the Federal Department of Infrastructure and Transport.

This means the engineering leg work has essentially been done for you, and the new GVM kit will be supplied with the correct certification and compliance plates; offering a higher GVM from day one, when fitted by an authorised agent. Sorry DIYers, this isn’t a task you can handle yourself.

There are numerous benefits when choosing pre-registration GVM upgrades, some of which we’ll touch on later in this article. However, the main one is cost, as it is a cheaper exercise due to an automotive engineer not being required to sign-off on the individual installation. This certification was completed when the suspension kit was tested for compliance and met minimum ADR safety requirements.

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Post-registration GVM upgrades

This is a bit more involved and expensive compared to pre-registration GVM upgrades, as the rules vary from state to state. We spoke with Simon Vella from Tough Dog about this, as he is a specialist in the field of suspension development and GVM upgrades.

“If you are wanting to perform a GVM upgrade on your vehicle post-registration, the process requires an Authorised State Engineering Signatory to inspect, validate and certify the upgrade, which takes place in all states and territories except for WA and NT,” Simon tells us.

“There is a different process in both Western Australia and the Northern Territory compared to other States in Australia that is based on a Type Approval System. This means for what we do at Tough Dog Suspension, we have a pre-approved upgrade approval agreement in place with the transport departments of either state and territory. Basically, for those living in WA or the NT it is not necessary to have a signatory to validate a Tough Dog GVM upgrade.”

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When asked about other states in Australia, Simon had this to say: “When it comes to the rest of the country, including Queensland, New South Wales, Victoria, Tasmania, South Australia and the ACT, it is a requirement to have a signatory certify any post-registration GVM upgrades. You will need an authorised state-engineering signatory to carry out the needed inspection and supply certification of an upgrade.

“The signatory may require access to our test data and reports for which Federal Approval (pre-registration) has been granted against, to validate the certification.

“We have a list of engineers on the Tough Dog website who can help with post-registration GVM upgrades. As we are NSW-based, we use John from Consulmotive in Peakhurst NSW, and the cost for this process usually costs around the $1000 mark, but this will vary from vehicle to vehicle and job to job, but gives you a ballpark figure.”

How much does it cost?

This is going to come down to the vehicle you own, and the components required to do the job. For example, the parts required to upgrade a VW Amarok to a maximum GVM of 3500kg using Bilstein shock absorbers and H&R coil springs will set you back $5899 from Advanced Installation Service in NSW’s Emu Heights. This is a drive-in-drive-out price, including parts, labour and engineering certification post-registration.

If we look at the Ironman 4x4 GVM upgrade for the petite JB74 Suzuki Jimny, increasing the GVM from 1435kg to 1785kg you are looking at an approximate minimum of $2571 pre-registration for parts alone, coming in at approximately $3000 for total install, ready to go. Post registration, this figure is reported to be around the $3700 to $4000 figure for the Jimny drive-in-drive-out, according to posts on various Jimny pages and forums found online.

If we look at the higher end of the scale, upgrading the rear axle to have a higher maximum axle load (and a track width correction) on a 79 Series LandCruiser, Brent from BAW Automotive in Queensland provided these figures for us.

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“Supply and install for GVM upgrades start from $17,000. This includes parts, labour and engineering,” says Brent. “With GVMs specifically, no brand allows just the sale of parts and all must be installed by trade professionals. Engineering and labour must be part of the package and can’t be costed out separately, as it gives the impression that you can just purchase the parts.

“In terms of costs at this stage, there aren’t huge differences – however, if we were talking about the 70 Series LandCruiser pre-registration, then it allows you to go higher than 50mm overall in suspension. At this height, it also allows the fitment of 35-inch tyres legally and compliant with federal-approved standards. Pre-rego you can also maintain your braked tow capacity, whereas with a post-rego GVM upgrade, it takes away from your braked tow capacity. In simple terms – post-rego, you won’t be able to tow items as big as you would if you’d sorted it pre-rego.”

“The maximum Gross Vehicle Mass upgrade you can achieve with a four-wheeled set-up is 4495kg, keeping it still driveable under a standard vehicle licence. You can move to a six-wheel set-up, but that’s a whole other kettle of fish and a whole different vehicle licence.”

Tyre and wheel load rating

It’s worth pointing out that if you increase the GVM of your vehicle, you might also need to look at upgrading your tyres and wheels, as the factory offering might not meet the new load-rating requirement. For example, if the rear-axle load limit is 3000kg, each rear wheel will need to be rated to 1500kg or above to handle this load legally and safely.

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Tyres also have a load rating, with aftermarket Light Truck tyres generally offering a higher load rating compared to the passenger tyres fitted to most new vehicles. We won’t go into specifics as this is quite a rabbit hole, but tyre and wheel upgrades are something to be aware of when looking to upgrade your vehicle’s GVM and increase tyre size.

This is why you need to speak with a knowledgeable and experienced suspension specialist before conducting the work, so you do things right the first time and don't waste time and money.

What are the consequences of GVM upgrades?

When we caught up with Simon Vella from Tough Dog Suspension at the Sydney 4X4 Show, he said the number one question he received from punters at the show, especially those new to the 4x4 game, was if they need a GVM upgrade straight away?

The other main comment was from those who had saved up to build their dream vehicle, and did a GVM upgrade, but the vehicle was now borderline dangerous to drive when unladen. This is because the spring rate used in GVM upgrade kits is much higher than factory to cope with the increased maximum load. Take that load out, and the vehicle is now over-sprung.

“The number one thing people need to do when it comes to GVM upgrades, is qualify their vehicle to determine if they need a GVM upgrade,” Simon told us. “Load your vehicle up, put it on a set of scales and weigh it, so you know exactly what your vehicle weighs trip-ready before deciding you need a GVM upgrade.”

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Apart from the expense of undertaking a GVM upgrade, end users are reporting poor ride quality unless loaded up, additional component costs, and the fact you must run all part numbers specified on the GVM upgrade kit.

So, if for example you want to run longer shock absorbers in an attempt to gain more suspension travel, you can’t. You have to use every item that came with the GVM upgrade kit, which is signed off by an automotive engineer as part of the approval process.

Having witnessed the approval process personally, I can confirm the engineer will inspect the vehicle, and take pictures of every part number of every part upgraded, to see that they match perfectly the part numbers listed by the manufacturer of the GVM upgrade kit. So, while a GVM upgrade is a useful inclusion for many four-wheel drive tourers, they aren’t for everybody.

With thanks

Big shout out to the following people who helped provide information for this article. These companies specialise in 4WDs and suspension upgrades, as well as GVM upgrades.

Simon from Tough Dog Suspension

Phone: (02) 9672 8899
Website: toughdog.com.au

Brent from BAW Automotive

Phone: 0417 783 415
Website: bawauto.com.au

Jeremy from Advanced Installation Services

Phone: (02) 4739 9009
Website: advancedinstalls.com.au