Light vehicle mass re-rating

This information is for the assistance of people who intend to re-rate their motor vehicles. It applies to motor vehicles with a Gross Vehicle Mass (GVM) no greater than 4500kg.

The load carrying capability of a light vehicle is determined from the Gross Vehicle Mass (GVM) rating. The GVM is the total permissible mass of a light vehicle and the load it carries (a light vehicle is one with a GVM of no more than 4,500 kg.

The Braked Towing Capacity (BTC) is the maximum loaded mass of a trailer (fitted with brakes) that may be towed by a light vehicle.  For a trailer that does not have brakes the maximum loaded mass is 750 kg.

These ratings are chosen by the manufacturer, taking into account the strength of critical components (such as axles and tyres) and meeting their customer’s expectations of ride comfort, handling, braking and durability. The configuration provided is ultimately a compromise to achieve a satisfactory balance to accommodate a wide range of vehicle uses and loading conditions.

Often a vehicle owner may require an increase in the GVM and/or BTC of the vehicle. This will mean accepting a different compromise from that determined by the vehicle manufacturer.  Upgrades may be required to springs and dampers, tyres and the cooling capacity of both engine and gearbox.  This will affect the ride comfort, handling and braking characteristics and the capacity of components such as axles.

Careful analysis and testing by a South Australian Light Vehicle Engineering Signatory (LVES) will be needed to ensure the vehicle remains safe to drive and compliant with applicable Australian Design Rules (ADRs). Contact details for South Australian LVES can be found in Fact Sheet MR426

It is important to realise that if the increased GVM is more than 4,500 kg the vehicle becomes a heavy vehicle.  It must be registered and insured as a heavy vehicle and the drivers will need to have a heavy vehicle licence (class LR, MR, HR or HC).  More information can be found on the Heavy Vehicles web page (www.sa.gov.au/topics/driving-and-transport/heavy-vehicles).

Second stage of manufacture

Vehicles may be purchased that have their GVM or BTC ratings change from the original manufacturer’s ratings while they are new (i.e. before first registration).

A vehicle that has a GVM and/or BTC rating increased by this process may be registered without requiring approval by the Department for Infrastructure and Transport (DIT).

Procedure

A vehicle owner who already owns a vehicle and wishes to have vehicle re-rated is required to submit an Application to modify a motor vehicle (form MR620) (482.3 KB PDF) to DIT prior to the modification being undertaken:

Post to:
Vehicle Standards
GPO Box 1533
Adelaide SA 5001

Email: vehiclestandards@sa.gov.au

Alternatively, the LVES may fill out the form on the owner’s behalf.

The Department will review this application and will issue the registered owner a Statement of Requirements (SOR) once it is satisfied that the modifications proposed will likely result in an acceptable outcome.

The SOR will specify the conditions that must be satisfied for the vehicle to be considered as meeting the standards for registration. These conditions will include the need for the LVES to provide a certification report that justifies the acceptability of the modifications undertaken and the new GVM or BTC.

The Department may require a roadworthiness inspection of the vehicle following receipt of the certification report.

Once all requirements listed on the SOR have been satisfied, The Department will issue a Certificate of Exemption (COE) for the vehicle, thereby approving the modifications and re-rating the GVM.

Requirements for vehicles seeking GVM re-rating

Vehicle manufacturers apply GVM ratings to vehicles on the basis of meeting their expectations for ride comfort, handling, braking and durability. The configuration provided is ultimately a compromise to achieve a satisfactory balance to accommodate a wide range of vehicle uses and loading conditions.

Often a vehicle owner may require an increase in the GVM of his or her vehicle. This will mean accepting a different compromise from that determined by the vehicle manufacturer. This typically results in upgrades to vehicle springs and dampers and the selection of alternative tyres, all of which will affect the vehicle load carrying capacity, ride comfort and handling and braking characteristics.

In many circumstances, the carrying capacity (GVM) can be upgraded following these modifications.

There are several mechanisms that can be used to achieve a GVM upgrade, and these are listed in the following sections.

When the GVM upgrade does not exceed the original manufacturer’s specified axle load capacity:

  • This will require an upgrade of the vehicle springs to a higher load rating than the standard springs.
  • The LVES will assess the suitability of the modified suspension for the GVM proposed.
  • The LVES will address the structural adequacy of the vehicle at the higher GVM.
  • The LVES will address the braking performance at the higher GVM. This may require testing of the vehicle at laden mass.

When the GVM upgrade exceeds the original manufacturer’s specified axle load capacity:

  • This will require an upgrade of the vehicle springs to a higher load rating than the standard springs.
  • The LVES will assess the suitability of the modified suspension for the GVM proposed.
  • The LVES will address the structural adequacy of the vehicle at the higher GVM.
  • The LVES will address the braking performance at the higher GVM. This will likely require testing of the vehicle at laden mass.
  • The LVES will assess the axles and suspension components to cope with the increased loadings beyond the OEM ratings. This will be likely to require detailed engineering analysis addressing stress and fatigue elements.
  • The LVES will assess the wheel and tyre loading requirements, and if these differ from the OEM tyre placard, then a new placard must be fitted to the vehicle replacing the OEM placard.

In addition to the above requirements, the following criteria may also be specified on the SOR depending on the modifications proposed:

  • Where the GVM increase is greater than 20%, evidence to confirm the braking system has been tested at a higher GVM including full brake test report as required by Fact Sheet MR132 Brake system test procedure (167.2 KB PDF), when loaded to the new GVM.
  • If the vehicle is fitted with any form of Electronic Stability control, evidence will be required that the system has not been affected by an increase in GVM.
  • A vehicle modified where the total lift (tyres plus suspension plus body) is more than 50mm beyond the original manufacturer’s standard height will require a Lane Change Test as required by Fact Sheet MR807 (376.4 KB PDF).

When the GVM upgrade is performed using an approved kit that has a Second Stage of Manufacture Identification Plate Approval:

  • If the vehicle is being re-rated under the SSM scheme prior to first registration and is fitted with an SSM plate, no action is required from Vehicle Standards.
  • If the vehicle is being re-rated under the SSM scheme after first registration, then the process is the same as for section 1 or 2 above, depending on the GVM rating, except that the LVES may be able to access the engineering analysis and testing undertaken by the SSM IPA holder that justifies compliance of their kit with the listed requirements. Otherwise, the LVES will have to undertake this analysis and testing to satisfy the listed requirements in the same manner as a kit that is not covered by an SSM IPA.
  • Vehicle Standards reserve the right to require a copy of this information to be provided with the Certification Report.

Note: Reduction of a vehicle’s GVM is allowed only if the original manufacturer provides an alternative GVM option for that vehicle.

Requirements for vehicles seeking braked towing capacity re-rating

A vehicle’s towing capacity is determined by the manufacturer with consideration to all aspects of the vehicle including:

  • chassis strength
  • engine and transmission capability
  • engine cooling package
  • axle ratings
  • suspension components
  • brakes
  • wheels and tyres
  • towbar rating and attachment
  • ball weight limits.

In order to re-rate towing capacity

  • An LVES must certify the vehicle on an individual basis if it conforms to the specifications of a variant produced by the vehicle manufacturer or it conforms to the specifications of a vehicle produced by a Second Stage Manufacturer.
  • The LVES must be able to show by manufacturer’s specifications and or component upgrades or analysis that the critical components can withstand the increased loads.
  • The LVES must ensure that the vehicle complies with performance requirements where required.
  • The LVES must ensure that the re-rated vehicle, with all any other modifications, is tested to ensure that the vehicle’s dynamic behaviour has not been unduly degraded.
  • The mass re-rating work must be assessed by an LVES to ensure that the vehicle remains compliant with the applicable Australian Design Rules (ADRs).
  • Where the vehicle re-rating requires modification, all vehicle modifications must be assessed by the LVES.
  • It is recommended that a modification plate is fitted, stating the revised rating and including the VIN and sufficient information to identify the modifier. This plate shall not be a heavy vehicle modification plate.

LVES certification report

The LVES is required to have inspected the vehicle to confirm the vehicle particulars and that the proposed modifications have been carried out correctly.

The LVES must provide the certification report to Vehicle Standards in writing, which includes:

  • details of the vehicle
  • details of the modifications
  • justification for acceptance in accordance with the above criteria

Page last updated 23 September 2020

Provided by:
Department for Infrastructure and Transport
URL:
https://www.sa.gov.au/topics/driving-and-transport/vehicles/vehicle-standards-and-modifications/light-vehicle-mass-re-rating
Last Updated:
23/09/20
Printed on:
29/09/20
Copyright statement:
SA.GOV.AU is licensed under a Creative Commons Attribution 4.0 Licence. © Copyright 2020
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