GVM/GCM Upgrades FAQ

What is a GVM?

Your car's GVM is the maximum weight your car can be when resting on all it's wheels with all it's people, luggage, fuel, accessories and towball weight attached.

Why would I need a GVM Upgrade?

The difference between the kerb weight and GVM on most passenger wagons is around 600Kg, this is called the payload capacity. On a ute it may be up to 1000Kg. If you add heavy accessories, such as bullbars and drawers, fill the car with fuel and passengers and then connect a trailer to the towbar you can exceed the payload capacity and be breaking the law (and jeapardising your insurance).

What is a GVM Upgrade?

A GVM UPGRADE is, essentially, a suspension kit that has been designed by engineers to improve the payload capacity of the car by changing the height and stiffness to better cope with higher loads, plus any complementary modifications like tyre load rating, indicator type etc. To make it a legally recognised upgrade it has gone through a rigorous process to prove that a) it works as intended, b) it doesn't compromise the ride, handling and safety systems of the car, c) the car still meets all Australian Design Rules (ADR's) applicable to the car and, is fully backed (warranted) by an Australian registered company. The warranty and traceability requirements demanded by the government mean that manufacturers only allow GVM Upgrades to be installed by facilities they regulate. The process to develop and certify a kit can cost up to $200,000, hence the 'fee' you pay vs buying a set of springs and shocks from eBay.

Why don't car manufacturers produce their cars with higher GVMs?

In the race to get you to buy their car - instead of one from a competitor - they need to make it as comfortable as possible. Comfort and load carrying ability are opposite to each other and 'about 600 Kg' seems to be the amount of payload OEMs feel is a good tradeoff between comfort and utility. Ute's are a solution with a higher capacity, but we do see most of them are not built for carrying their maximum load for more than a short time before springs become permanently deformed. A light truck is an example of a vehicle designed for carrying higher payloads with the resultant compromise in comfort - families don't want that type of vehicle for everyday use!

What is a GCM?

The Gross Combined Mass (GCM) is the maximum weight of a combined car and trailer. This might be measured 'as combined' if you have a large weighbridge, or as separate weights combined on paper.

Why would people need GCM Upgrades?

There are several reasons people start thinking about their GCM - a) most often they've bought a bigger caravan/trailer than their existing car can tow, b) the weight of accessories added to the car has consumed too much payload and there's no longer enough, or c) have the bigger van and want to change their car without moving into a large American truck (ie upgrade the new car to have the higher GCM instead).

What is a GCM UPGRADE?

A GCM UPGRADE is an extension of a GVM UPGRADE. It takes the GVM Upgrade and then does about twice as much engineering verification to confirm that the car is a) safe to drive with the higher loads, b) the drivetrain is strong enough for the higher loads, c) the performance (acceleration, handling and braking) of the car is still acceptable, the added stress on the drivetrain is considered and complementary modifications are either included or recommended. A standard GVM UPGRADE does not take these matters into consideration and companies cannot offer them without having the proof to ensure their product is safe and warrantable to the consumer.

Are there other modifications I should consider?

All towing puts stress on the car, particularly the automatic transmission. Even if towing moderate loads under heavy conditions (eg mountainous) it's advisable to install a (bigger) transmission cooler. Some vehicles, eg LC200 and Prado, will also benefit from having a torque converter lockup system installed to prevent slippage and heat buildup. We can talk to you about those extra modifications in-store.

What are the main things that cause isues when doing a GVM/GCM Upgrade?

  • Tyres of incorrect width for their rim (common on D-Max with their skinny factory wheels).
  • Tyres that are smaller than the tyre placcard stipulates
  • Tyres that don't meet, or exceed, the load rating stipulated on the tyre placcard
  • Tyres larger than the ADR allows - you can change diameter up to 25mm without incurring adidtional engineering expense (if they can be complied at all). 35" tyres might look tough, but they are rarely legal if the OEM didn't have a tyre that large in the first place.
  • Wheels that are not rated more than the minimum to exceed the axle requirements of our kits.
  • Wheels with offsets more than 25mm from the OEM wheel. The ADR only allows track width changes of 50mm from standard. Most aftermarket wheels fail this requirement. 
  • Exhausts that have catalytic converters or DPFs removed. 
  • Maintenance issues - worn ball joints, brake pads, suspension bushes etc

Someone in a store told me you can't do a GCM Upgrade,is this true?

Absolutely not, the federal government and TransportSA both have engineering rules allowing GCM increases. We follow those rules and have been doing GVM and GCM increases for many years.

I read online that GCM Upgrades are illegal, is it true?

Absolutely not, the federal government and TransportSA both have engineering rules allowing GCM increases. We follow those rules and have been doing GVM and GCM increases for many years. The rules do vary from state to state and so you're best to seek advice from local businesses rather than an interstate keyboard warrior with no actual qualifications or experience in vehicle engineering and certification.

I'm getting a new car soon, how do I get a GVM Upgrade?

Consult with us as to your requirements and the solution we can offer.

Advise your new car dealer that you want a GVM Upgrade done prior to first registration, and where it's to happen

Dealers have differing processes, some may want you to pre-pay for the car before it leaves their premises, some may want you to pay for towing fees, some may try to steer you elsewhere if they have an affiliation with another company (kickback?).

My car is already registered, what is the process to do a GVM/GCM Upgrade? (note:- times suggested are 'typical' and beyond our actual ability to manage)

Consult with us as to your requirements and the solution we can offer.

Make a booking for installation, typically this can vary from next day to four weeks depending upon stock and workshop constraints

DAY 0 :-

Fitting of the kit (plus any other works we're doingfor you) in our workshop.

Engineering inspection at our workshop (we take care of the booking for this)

Day 7-14 :-

    Engineer's report is released and the modifcation request lodged with TransportSA

Day 28 - 42 :-

    TransportSA send you either an exemption for inspection or a request to book an inspection at one of their sites around the state. You have twelve months     from the date of their letter to get the inspection done before a new engineering report is required.

INSPECTION DAY :-

    Present the vehicle to TransportSA for inspection. This is a full roadworthy checking lights, tyres, seatbelts, exhaust systems (still got our catalytic converter     in place?), wear and tear etc.

    Presumably the inspection has gone well and you drive out with your car now fully complied to the new GVM/GCM figures.

NEXT DAY :-

    Don't forget to tell your insurance company because the value of your car has now increased and it's considered a big modification that most policies     oblige you to tell them of.