Everything you wanted to know about GVM Upgrades but were scared to ask. Key terms explained - payload, GVM, GCM, Tare Weight, Kerb Weight etc. Pre and Post registration rules explained. And things to consider before an upgrade.
GVM Upgrades 101
GVM Upgrades are something pretty simple right? I mean, your vehicle comes with a certain payload which pretty quickly gets used up with upgrades an modifications, and by doing a GVM upgrade you get more payload. Article complete, problem solved!
If only this were the case! Unfortunately in this country, there are a myriad of complexities around GVM Upgrades, which often vary by state. The purpose of this article is to help you understand the system and process in Australia for GVM upgrades, where they differ, what they actually do and what they don’t do, and how you can navigate this.
Basic Terms Explained
GVM stands for Gross Vehicle Mass. It is the maximum weight that your vehicle is certified to be. If you exceed this, your vehicle could become unsafe to drive, could void warranty, or even void your insurance.
Tare weight is the weight of the vehicle without any fluids or oils, as it comes from the factory. Any modifications or upgrades post manufacturing will render this stamped weight on your vehicle wrong.
The kerb weight of your vehicle is the base weight of your vehicle with all permanent fixtures and fittings, all oils and fluids and a full tank of fuel. This is the weight that you should plan off.
This is the amount of additional weight that you can add to the vehicle and can be calculated by subtracting the Kerb Weight from the Gross Vehicle Mass. If you have upgraded your vehicle from OEM specifications, you should go to a weighbridge and calculate. It is also important to remember that your passengers form part of your payload, so you subtract 80-100KG of weight from your payload for each person travelling in the vehicle to ensure that you don’t exceed GVM.
The Gross Combined Mass is the Maximum combination weight that a vehicle and anything it tows can weigh. This is specified by the manufacturer and generally can’t be changed. More importantly, most vehicles GCM is less than the sum of the GVM and the braked towing capacity, meaning that you can’t load a vehicle up to GVM and then tow the maximum braked towing capacity.
Second Stage Manufacturing – Pre-registration, under federal legislation, vehicles can undergo modifications and upgrades by registered Second Stage Manufacturer, which can then certifies them nationally for the upgrades.
Front and Rear Axle Weights
These are the maximum allowed weights on the front and rear axles, which usually add up to slightly more than the GVM of the vehicle. The rear axle weight is usually greater than the front, but it is important that these are not exceeded when loading your vehicle.
National and State legislation for upgrades and where it applies
Before a vehicle is first registered, upgrades that are made to it through a Second Stage Manufacturer apply nationally – I.E – in all states. Essentially once a SSM process is completed, the roads and traffic bodies recognise the modifications to the vehicle as being stock (they are engineered through this process). The implication of this is that if the vehicle is sold to someone in another state, or you move, then the vehicle remains legal in all states.
The SSM process is only available before a vehicle is first registered though, because after it is first registered, the vehicle is now subject to state legislation which varies. This means that post-registration, any upgrades or modifications must adhere to the state based legislation on modifications which often vary.
It also means that if you get a GVM in NSW, that engineering certificate only covers that modification in NSW. I.E – if you move to QLD and want to register the vehicle there, you will need to pay for a QLD approved engineer to certify the vehicle in QLD.
What a GVM Upgrade doesn’t do
GVM upgrades are designed to allow the vehicle to carry more weight, but upgrading a GVM will not generally increase your GCM. This means that while you can increase your GVM to carry more weight, there is no change to the GCM, meaning that while the vehicle can carry more weight, you can actually tow less when the vehicle is loaded to the new GVM than you could pre-GVM upgrade.
Some businesses are out there including GCM upgrades, or braked towing capacity upgrades, but the legality of these upgrades is questionable. We recommend that you seek independent legal advice before relying on these certifications yourself.
Why you need to think carefully about who and what upgrade you should do
Many vehicles have payloads that quickly disappear with some minor upgrades like suspension and barwork, making a GVM upgrade a necessary choice for those that want to head offroad and be legal and safe.
The big mistake we see many people making is going for the biggest payload increase that they can. While this might seem like a good idea ‘just in case’, the number one thing you need to consider when selecting your suspension is how much weight you will be carrying the majority of the time.
If you do select the biggest upgrade possible, but you are not carrying that amount of weight all the time, then the suspension setup will be too stiff because it was designed to carry half a ton or more of weight which is actually not in the vehicle.
That lack of weight will make the vehicle handle poorly, and the ride quality will be poor most of the time, only actually working when the vehicle is loaded to that level.
For this reason, it is very important that you set the vehicle up for what it will be carrying most of the time, and only upgrade the GVM to the lowest additional weight that you need.
We’re here to answer any questions!
At Solve, we are experts in GVM upgrades. We understand the different characteristics of various makes and models, and we fit and supply a range of GVM kits from different manufacturers. This allows us to offer you the right solution to your situation and vehicle setup.
If you’ve got questions about GVM and upgrades, we’d love to hear from you.