In this Cruisemasterclass, we'll explore the intricacies of GVM (Gross Vehicle Mass) upgrades and some of the processes involved in carrying this out. We'll discuss the differences between SSM (Secondary Stage Manufacture) and in-service modifications, as well as the critical aspects that go into a successful GVM upgrade.

Cruisemasterclass episode 20: GVM Upgrades

SSM and In-Service Modifications

There are two ways to obtain a GVM upgrade for your vehicle: before original registration through a Secondary Stage Manufacture (SSM) program, and after registration via an in-service modification. 

For 'pre-rego' GVM modifications there are a few options on the market with SSM approval for their kits, these include Pedders, ARB, and JMACX. 

An example of this is the JMACX 4200kg GVM upgrade kit fitted to a pre-registration 79 Series Landcrusier by the Towing Performance Centre. In-service modifications use the SSM-approved system as a basis, but with an additional step in the process. 

This typically involves an approved person going through a checklist to ensure the vehicle meets all necessary requirements in order to get a compliance plate fitted to the vehicle for the new rating.

GVM Upgrade Compliance Testing

For SSMs to be approved there is a variety of compliance tests that the modified vehicles must go through, these include but are not limited to;

ADR Brake Testing

This test checks whether a vehicle can decelerate the new load, what happens during a partial circuit failure, and whether it can hold itself up on a specified handbrake hill. Below is an example of what the handbrake hill testing involves, with an upgraded Ford Ranger on a 30% incline.  

Electronic Stability Control (ESC)

ESC ensures that the vehicle remains stable and on course during aggressive evasive maneuvers. During GVM testing a steering robot is used to confirm the ESC is still operational and hasn't been affected by the changes to the vehicle's weight.

Component Strength Testing

Components like diff housings, control arms, and knuckles are all assessed for their ability to handle increased load and Australian conditions. 

This is often done using finite element analysis, by breaking down the individual components, assessors will scan them to get physical sizes and material composition to evaluate if they can handle the increased load. Below is an example of what the AIC (Auto Innovation Centre) analysis looks like on a diff housing. 

Light Positioning

As vehicles are sometimes lifted during the GVM upgrade process, their lighting positions may need to be modified to remain compliant with ADRs. 

This is the also the case when the vehicle enters a new vehicle category under the ADR classifications, and often requires additional lighting to be fitted.

Things to Consider Before a GVM Upgrade

GVM Upgrade Effects Vehicle Warranty

In most cases an approved GVM will not affect a vehicles warranty, however It's important to note that this may not be the case for all makes, models or GVM upgrade kits.

Make sure that before proceeding with any modifications, you consult with the vehicle manufacturer or dealer to understand any potential impacts on your warranty to ensure you are not inadvertently voiding it.

Vehicle Registration and Insurance Changes

A GVM upgrade may also affect your vehicle registration and insurance. Ensure you inform your insurance company about the modifications, as failure to do so might result in denied claims in the event of an accident. 

In some cases upgrading the GVM can increase the value of the vehicle so make sure to have it reassessed. Additionally, check with your local transport authority to understand any registration requirements related to the GVM upgrade. 

Upgrading your vehicles Gross Vehicle Mass above 4.5T changes the vehicles class code and will require a Light Rigid Drivers License.

Wheels and Tyres

With the increase GVM, It's essential to ensure that the wheels and tyres are suitable for the increased load. The wheel's rating can usually be found cast inside the spokes, while the tire's capacity is displayed on the sidewall.

Consult a Professional

A GVM upgrade is a complex process that should be handled by experienced professionals for installation. Consult with a reputable workshop or vehicle modification specialist to discuss your needs and ensure the upgrade is done correctly and in compliance with all relevant regulations.

GVM Upgrade Examples

To better understand GVM upgrades, let's examine a real-world example: the Crusiemaster Toyota Land Cruiser with a JMACX 4.2T GVM upgrade. 

As part of the kit, this Landcruiser has a custom-fabricated diff housing, springs, shocks, and control arms capable of handling the additional load. Due to the change in vehicle height, the front of the vehicle has replacement control arms to help maintain wheel alignment. 

The factory wheels and tyres have also been changed to a set of rated ROH wheels and Kenda Tyres to remain compliant with the vehicle's tested requirements.

GVM Upgrade Documentation

All critical information regarding a GVM upgrade is usually displayed on stickers placed on the vehicle. For an SSM vehicle, you'll find a federal sticker showing the new GVM and the vehicle's VIN number. 

An axle load capacity sticker will also display the vehicle's axle capacities with the modifications, legal tire size, and tire pressures.

Understanding GVM upgrades can be complicated, but with the right knowledge and resources, you can make informed decisions before modifying your vehicle. If you have any GVM-related questions, feel free to contact Cruisemaster's Towing Performance Centre.

For more caravan and towing tips, make sure to keep an eye out for the latest episodes of our Cruisemasterclass series by subscribing to the Cruisemaster YouTube channel and following us on Facebook & Instagram.