Search the title of this blog and you will get a lot of answers. All the following information is correct at December 2022. The information applies to Queensland registered vehicles. Wait, why only Queensland? I am going to try to keep this simple. The truth, this is messy.
Why only Queensland?
Modified cars, registration and a number of road rules differ in every state. Being based in Queensland I deal with the QCoP (QLD code of practice) and the NCoP (National code of Practice also called VSB14). The QCoP takes position over the NCoP. How a car can legally be modified in another state can and does differ to QLD. Mostly I see vehicles requiring MOD plates or Blue plates for Vehicles that have been modified in QLD, NSW and VIC.
The answer to the question of how large a tyre can be fitted to a 4WD (Class MC - OFF-ROAD PASSENGER VEHICLE - A passenger vehicle having up to 9 seating positions, including that of the driver and being designed with special features for off-road operation) in QLD is 50 mm larger than the largest tyre fitted to that model. That is 50 mm larger is diameter. Using a 50 mm larger diameter tyre will give a 25 mm increase in ride height. The NCoP states the same 50 mm increase in tyre diameter.
How exactly that was decided on I am not aware. QCoP LS9 states “the increase in ride height from suspension, tyres and body blocks must not exceed 100 mm suspension, 25 mm tyre and 50 mm body blocks. The code also requires that the combined increase in ride height must not exceed 150 mm. The same document also states “Lift modifications that are outside the scope of LS9 as explained above, require specific approval from the Department of Transport and Main Roads (TMR).
I recently had a vehicle to inspect for transfer of registration that was purchased from NSW. That vehicle had a tyre size increase of 80 mm and a 3 inch suspension lift. Reciprocal approval can be applied for any modification that was performed and approved interstate. Reciprocal approval simply means, paperwork is completed and the documents submitted from when the original modifications were performed. Often this will negate the need for inspection and testing to be performed a second time. This vehicle had approval for the 80 mm tyre size increase and 3 inch suspension lift in NSW. The LT2 (lane change manoeuvre test) and brake test had been performed with passing results.
Before applying for reciprocal approval or specific approval for the tyres size increase and email was sent to vehicle standards. Now it is completely correct in sending an application for reciprocal approval or specific approval. That is the correct process. The response was as follows, Specific approval will be granted on an as needed basics. If you need larger tyres for a specific use vehicle like an emergency vehicle, a vehicle used for inspecting fire trails or an agricultural vehicle approval maybe granted but is not guaranteed.
Want larger tyres because they look cooler or you go on the beach once a month is not an approval that will be granted. Reading between the lines approval will not be granted for a nonspecific use vehicle.