Wheels which exceed the diameter and width limits for major wheel changes must be assessed by an engineering signatory who is recognised by the Transport Authority for the purpose of certifying modified vehicles. (Contact the Transport Authority for more information.)
If the signatory finds that the wheels are safe for your vehicle, you will be issued with an engineering certificate. The original of this certificate is generally required to be submitted to the Transport Authority for notification of the modifications, or for registration of the vehicle. The duplicate copy or owners copy is stamped and endorsed by the Transport Authority, and must be kept in the vehicle to be presented to an authorised officer of the Transport Authority or the police, when requested.
There are limits on the size of wheels, which can be certified by an engineering signatory. These limits are as follows:
The maximum permitted rear rim width for a particular vehicle is determined by its tare weight (10 litres of fuel, no occupants or luggage) in accordance with the following table:
The lesser of each front wheel shall be:
- no wider than the maximum permitted for rear wheels on your vehicle or 204mm
- no narrower than 70% of that fitted to the rear wheels, and
- no narrower than a standard wheel fitted to your vehicle as original equipment.
Front Wheel Drive Vehicles
For these vehicles, except where the original manufacturer provides to the contrary, front wheel widths shall be no more than 26mm greater than the widest optional wheel offered by the vehicle manufacturer. This requirement also applies vehicles with constant four wheel drive.
Four Wheel Drive Vehicles
For these vehicles, except where the original manufacturer provides to the contrary, the maximum wheel width is the lesser of the maximum for rear wheels on your vehicle or 204mm, the front and rear wheel widths shall be the same.
Vehicles with diagonally split brake systems
Except where the original manufacturer provides to the contrary, vehicles so equipped must have the same size wheel widths fitted to front and rear wheels. The front wheel offset (and front wheel track) shall remain as original.
Additional Requirements for Replacement Wheels
- The wheel rim width must not be less than the minimum width fitted by the vehicle manufacturer for the particular model.
- The wheel and tyre must be contained within the body work, or mudguards, including "flares", when the wheels are in the straight ahead position.
- The wheel and tyre must not foul any part of the body or suspension under all operating conditions.
- All wheels fitted to "an axle" must be of the same diameter, offset, width and mounting configuration (except for spare wheels used in an emergency situation)
- Wheel nuts & bolts (studs) must have a thread engagement length at least equal to the tread diameter, except where specified otherwise by the vehicle manufacturer.
- The wheel rim must not have a circumferential weld other than that which attaches the rim to the wheel centre.
- The wheel must be one designed for the particular hub/axle in respect to bolt pitch circle diameter and wheel nut tapers. Wheels with slotted stud holes are not permitted.
- Speedometer accuracy must be maintained for the selected tyre and rim combination.
- The fitment of wheel spacers (or adaptors for dual wheel conversions) between the wheel mounting face and the road wheel is not permitted unless fitted as original equipment by the vehicle manufacturer.
- The maximum legal permissibile increase in the vehicle's track width in most states of Australia is 25mm and others 26mm. Most states subscribe to the National Code of Practice, which stipulates a maximum track increase of no more than 25mm. Care must be taken, therefore, not to fit wheels having wheel offsets that would create the vehicle track width to increase in excess of 25mm.