Do I Need A GVM Upgrade For My 4x4?
Learn how to identify your 4x4 and trailer's weight limits and discover whether you need a GVM Upgrade for your 4x4.
Get to know your 4x4 and GVM limits
Overloading your vehicle illegal but it’s also unsafe. When you carry more weight than the vehicle is rated to handle, it forces the engine, suspension, axles and brakes to work harder than designed. This compromises the longevity of the vehicle and your safety on the road.
We'll cover the technical terms, tips on checking your vehicle weight and how your local Ironman 4x4 dealer get help dial in your suspension set-up.
Video: What are your GMV upgrade options
Sometimes it’s best explained in a video.
Watch Robert Pepper, Automotive Journalist, explain what a GVM upgrade is and why you need one.
Tune in on YouTube.
Vehicle weight technical terms explained
There are lot of technical terms thrown around when talking about vehicle and towing weights. We get that it can be confusing and sometimes seem all too hard, so we’ve tried to simplify it for you below.
Tare Weight
The tare weight is the total weight of your vehicle when it has left the manufacturer. This generally doesn’t include any after sales accessories you have chosen to add to your vehicle.
If you have additions added to your vehicle at the time of purchase it is good to check what is and isn’t included in your tare weight.
Vehicle Payload
The payload is the allowable amount of weight you can put in your vehicle. Sometimes this is provided by the manufacturer, but it is simple to work out by subtracting the kerb weight from the gross vehicle mass.
Hot tip: always keep in mind that your payload needs to include fuel, larger tyres and any passengers onboard at that time.
Axle Limits
The axles, suspension and shocks in your vehicle are designed to comfortably carry a specific amount and percentage of weight across your vehicle.
The vehicle manufacturer sets a maximum weight that each axle can carry based on the OEM specification suspension. This can be upgraded with a GVM upgrade.
Gross Vehicle Mass (GVM)
The gross vehicle mass, commonly known as the GVM, is the maximum amount of weight you can carry in your vehicle. This includes any passengers, fuel, vehicle accessories and luggage.
If you are towing, this weight also includes your trailer ball weight. It is set by the vehicle manufacturer but like the axle limits can be upgraded with a GVM upgrade.
Vehicle Tow Capacity
Any tow vehicle has a maximum towing capacity set by the vehicle manufacturer. This includes the maximum tow weight and the trailer ball weight permittable.
Tow Bar Tow Capacity
Each tow bar has its own maximum tow capacity. Sometimes this can be different to the maximum vehicle tow capacity.
If the tow bar is rated higher than the vehicle, the maximum tow capacity of the vehicle is the Vehicle Tow Capacity.
If the tow bar is rated lower than the vehicle, the maximum tow capacity is the Tow Bar Tow Capacity.
Hot tip: All Ironman 4x4 Tow Bars are rated to the maximum set by the vehicle manufacturer.
Trailer Ball Weight
The trailer ball weight is the weight under the coupling of your trailer, creating a downward force on the tow bar.
The vehicle, tow bar and trailer can have maximum trailer ball weight ratings. The lowest rating of the three is the maximum Trailer Ball Weight for your set-up.
Trailer Tare Weight
The trailer tare weight is the weight of the trailer when it has left the manufacturer.
Note: In terms of camper trailers and caravans, if you have had additional accessories added, these may not be included in the tare weight and may contribute to your Trailer Payload. Check with your dealer at the time of purchase.
Trailer Payload
The payload is the allowable amount of weight you can put in your trailer. Sometimes this is provided by the manufacturer, but it is simple to work out by subtracting the tare weight from the gross trailer mass.
Hot tip: Your payload will include any accessories, luggage, fuel, water and load you add to the trailer.
Gross Trailer Mass (GTM)
The Gross Trailer Mass is the maximum trailer weight imposed on the trailer’s axle and chassis when coupled to the tow vehicle. This weight does not include the trailer ball mass.
Aggregate Trailer Mass (ATM)
The Aggregate Trailer Mass is the maximum trailer weight, when the trailer is not coupled to the tow vehicle. This means it combines the GTM and Trailer Ball Weight to provide the total trailer weight.
Gross Combined Mass (GCM)
The Gross Combined Mass is the maximum allowable weight of the tow vehicle, trailer and load.
Often it is assumed that the GVM plus the Vehicle Tow Capacity makes the GCM, however this is not always the case.
In many cases, the vehicle manufacturer has set their own GCM that the vehicle can move. Check your vehicle owner’s manual to find the right figure for your vehicle.
Weighing your 4x4
Weighing your 4x4 isn't a complex process, but there are a few thing you'll want to have prepared before you get started, including, knowing where your local weigh bridge is, your vehicle maximum weights and your trailer maximum weights.
Where to weigh your 4x4
There are many public weighbridges in Australia that allow you to weigh your vehicle and trailer for a small fee.
Find an Australian Government weighbridge here.
How to find your 4x4's maximum weights
For your vehicle maximum weights, including your tare weight, axle weights, GVM and GCM, check the owner’s manual supplied with your vehicle. If you cannot locate the weight information, contact the vehicle manufacturer.
How to find your trailers maximum weights
To find your trailer’s maximum weights, you will need to locate the compliance plate of your vehicle. This is commonly found in the front boot of a camper trailer and caravan or on the chassis of a trailer.
How to measure your 4x4 weights on a single deck weigh bridge
Roll the front axle onto the weighbridge and record the weight, then roll the vehicle forward until only the rear axle is on the deck and record the weight. Simply add the two weights to find your GVM.
How to measure your 4x4 weights on a multi-deck weigh bridge
As long as the axles are on each deck, it will record a separate weight for each axle and provide an overall GVM.
Hot tip: if you are towing, your Trailer Ball Weight needs to be included in your GVM.
If you're weighing the vehicle without the trailer attached, remember to add this weight afterwards as it contributes to your total GVM on the road.
Weighbridge Checklist: What vehicle weights to record
The measurements your want to take of your 4x4 include:
- Front axle weight
- Rear axle weight
- GVM: front axle weight + rear axle weight = GVM
How to weigh your trailer, camper or caravan on a weighbridge
To obtain the GTM for your trailer, tow your trailer onto the weigh bridge, making sure all axles are on the deck. Ensure the tow vehicle is not touching the decks and record the total trailer weight.
The trailer ball weight can be measured using a device like a tow ball weight scale or via a mathematical equation:
GVM (with trailer connected) – GVM (without the trailer connected) = Trailer Ball Weight
To find your ATM, you will need to measure your trailer ball weight.
The ATM of your trailer is the total weight of the trailer uncoupled from the vehicle. To find this weight, add the GTM to the trailer ball weight.
Weighbridge Checklist: What trailer weights to record
The measurements you want to take of your trailer, camper or caravan include:
- Ball weight: GVM (with a trailer connected) - GVM (without the trailer connected) = Trailer Ball Weight
- Gross Trailer Mass (GTM): Trailer weight connected to vehicle
- Aggregate Trailer Mass (ATM): Ball Weight + GTM = ATM
Choosing between a suspension or GVM Upgrade
You can move load and weight forward, backwards or even removing the load, but let’s face it, you want to carry what you want to carry comfortably and safely without a hassle.
A suspension upgrade is a great way to carry higher loads comfortably and safely. They're tuned to suit your vehicle and what you want to carry. Suspension kits can be set to carry a permanent load or a temporary load.
But, if you are overweight, a GVM upgrade could be your answer. A GVM upgrade can provide you the additional payload you need for your ideal vehicle set-up.
Why should I upgrade my 4x4 suspension?
Every time you add load to your 4x4, whether temporary or permanent, the responsiveness of the Original Equipment (OE) suspension changes. The OE manufacturer designs their suspension kits for comfort above all else and the addition of load can compromise ongoing performance.
Upgrading your suspension to suit what you are doing with your 4x4 can improve handling and safety on and off-road, and where weight is concerned it can keep your vehicle road-legal.
How to choose a suspension or GMV Upgrade for your setup
Suspension and GVM upgrades are designed to suit your specific circumstances. This ensures a solution that not only meets your needs but continues to produce outstanding results in the future.
Ironman 4x4 have range of solutions to fit your 4×4. But if you are looking for more specialised advice, your local Ironman 4x4 dealers are GVM experts.
- Explore Suspension Kits
- Explore GMV Upgrades
- Find your local Ironman 4x4 dealer