GVM vs GCM: What's The Difference?

GVM, or Gross Vehicle Mass, is the maximum permissable weight of a vehicle before adding a towed trailer or caravan. 

It refers to the maximum allowable weight of your vehicle when it’s fully loaded. This allowance includes everything from the vehicle’s weight to the occupants, fuel, cargo, and accessories on board. 

The vehicle manufacturer sets the GVM based on the upper operating limit of your vehicle’s suspension, brakes, tyres, and chassis. Going over this limit can have serious consequences; it can affect your handling, braking performance, and tyre wear.

Importantly, exceeding your GVM is illegal and may void your insurance.

So, if you’re planning on carrying heavy loads or adding aftermarket accessories, understanding your GVM is step one. If your setup exceeds your current rating, a GVM upgrade might be necessary to ensure you’re road-ready and compliant.

What elements are including in your GVM?

Here’s a breakdown of some components that contribute to your Gross Vehicle Mass:

Kerb weight: The weight of the vehicle with all standard equipment and fluids, excluding passengers and cargo.​

Payload: Includes passengers, luggage, tools, and any other cargo.​

Fuel: A full tank of fuel.

Accessories: Aftermarket additions like bull bars, roof racks, winches, or drawer systems.​

Towball load: If towing, your tow ball's "down" weight, or force exerted on the tow ball by a trailer also counts toward the GVM.

The GCM or Gross Combination Mass refers to the total combined weight of your vehicle PLUS any trailers or towed loads, all fully loaded, including passengers, cargo, fuel, and any additional gear or tools. 

It’s important to remember that your vehicle's GCM is a strict limit. While a GVM upgrade can improve your GVM to ensure safe operation when your vehicle is loaded, it will not increase the GCM of your vehicle. 

Exceeding this limit can strain your vehicle’s brakes, suspension, and overall handling, creating serious safety risks and greatly accelerating wear and tear on your vehicle, and could void your insurance policy or lead to legal penalties. 

To ensure you’re towing safely and legally, you should always keep track of your GVM and GCM to avoid exceeding these critical weight limits.

For further guidance on calculating your GCM and staying within legal towing limits, visit our GVM Upgrades Explained page.

Calculating GCM for your vehicle

Here is a step-by-step guide to calculating the GCM for your vehicle:

1. Identify the GVM of your vehicle: The total weight of your fully loaded vehicle, including passengers, cargo, and any accessories.​
2. Identify the GTM (Gross Trailer Mass): The maximum weight your trailer is legally allowed to weigh, fully loaded.​
3. How to calculate your GCM: Add the GVM of your vehicle to the GTM of the trailer.​

Example GCM Calculation:

GVM of your vehicle: 3,200 kg​
GTM of your trailer: 2,200 kg
Total GCM: 3,200 kg + 2,200 kg = 5,400 kg​

Note: It is essential to ensure that your combined weight doesn't exceed the GCM specified on your vehicle's compliance plate or owner's manual.​

While GVM and GCM are often mentioned together, they serve very different purposes when managing a vehicle’s weight. Knowing the distinction is key to staying safe and compliant on the road.

GVM is - The maximum weight your vehicle can carry on its own.​

GCM is - The maximum combined weight of your vehicle and any trailers or caravans it's towing.

Why knowing the difference matters

Understanding the difference between GVM and GCM is crucial for many reasons, such as:

• Safety: Staying within specified limits ensures optimal performance, braking, and handling.​

• Legal compliance: Exceeding either GVM or GCM can result in fines, loss of insurance coverage, and potential liability if you are in an accident.​

• Vehicle condition and performance: Keeping within weight limits helps prevent damage and excessive wear to your suspension, steering, and drivetrain components.

Does a GVM upgrade increase GCM?

A common misconception is that upgrading your vehicle's GVM also increases its GCM. 

While a GVM upgrade increases your vehicle's legal carrying capacity, it does not  increase the GCM. GCM is set by the original vehicle manufacturer and can only be changed through a secondary-stage manufacturer process, which is rare and highly regulated.

Managing your vehicle's load is something every vehicle owner that loads up or uses their vehicle to tow should be aware of, but it can be quite complicated. Thankfully as Australia's Tow and Load specialists, Pedders has some simple solutions to take away the guesswork and help you ensure your vehicle is legally compliant. 

Pedders Weight Matrix

Pedders Weight Matrix is a free online tool which provides an estimate of your GVM based on information you select for your vehicle. It can include common accessories, loads and towing items, and provides a detailed report highlighting your load, remaining capacity, weight distribution and additional braking distance – all referenced to original base weights for your vehicle.

Please note that the Pedders Weight Matrix is to be used as a guide only, as in some instances it uses assumptions or estimates to provide information that is as accurate as possible.

Pedders Tow and Load Assessment

To understand exactly what your vehicle's GVM is and know whether your legally compliant, the best available option is to book a Pedders Tow and Load Assessment.

A Pedders Tow and Load Assessment is undertaken by our expert team to give your vehicle a comprehensive test of brake, steering and suspension components, weighing your vehicle, a checklist of your accessories and towed loads to produce a comprehensive, no obligation report. 

To make sure your vehicle is safe and legal before your next trip, book in a Pedders Tow and Load Assessment today.