Thanks to JAXQuickfit Tyres website for the info below..
Wheel Fitments
Wheels up to 26mm wider than the largest optional wheel recommended by the vehicle manufacturer for the vehicle can be fitted without the need to notify the RTA. The overall diameter of the wheel and tyre combination must be no more than 15mm over the largest diameter wheel and tyre combination specified for the vehicle, and not more than 15mm below the smallest diameter wheel and tyre combination specified for the vehicle.
Replacement Wheels Requiring an Engineers Certificate
Wheels which exceed the diameter and width limits for minor 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:
Rear Wheels
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:
Front Wheels
The lesser of each front wheel shall be:
1. no wider than the maximum permitted for rear wheels on your
vehicle or 204mm
2. no narrower than 70% of that fitted to the rear wheels, and
3. 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 wheeltrack) shall remain as original.
Additional Requirements for Replacement Wheels
When wheels (and tyres) outside the manufacturers recommended range are fitted to a vehicle, the following requirements must be met:
• 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 straight.
• 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) • The wheel must not prevent the wheel nuts from fully engaging
their studs.
• 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.
Christina hope that this answers all your questions that you have on what size tyres and what you need to do, if not maybe you should ring up your nearest tyre professional and ask them for their unbiased opinion. :whistling Just my 2c worth:whistling
Sorry about the long post knew that I had seen this info before and had a little trouble finding it.
Cheers.