Motor vehicles and their components are subject to many complex but necessary safety standards, and tyres are no exception.
The Australian Design Rules (ADR) specify several important requirements relating to passenger vehicle tyres and wheels, with separate regulations in place for trucks and construction vehicles.
Australian Design Rules (ADR) for Tyres
ADR 23 stipulates that all cars must be fitted with a label or placard that clearly documents the correct tyre specifications, including size, capacity rating, speed rating, and suggested inflation pressure, according to the manufacturer’s requirements. This rule has been in place since 1973.
Interestingly, ADR 23 does not mandate what construction style the tyres must have, meaning that older tyre styles can still be sold and fitted. However, tyres must meet performance standards, such as heat resistance, endurance, strength, and high-speed stability.
Tyre Labelling Requirements
In addition to performance standards, tyres must have their specifications—such as size, construction type, speed rating, load rating, and date of manufacture—clearly printed on the sidewall. For asymmetrical tyres, an arrow must indicate the correct direction of fitment. Furthermore, tyres must feature a minimum of four equally spaced tread wear indicators. These indicators are designed to show when the tread is 1.6mm or less, which is the point when the tyre is no longer considered roadworthy.
Replacement and Aftermarket Tyres
When replacing tyres on passenger vehicles, the new tyres must not be more than 15mm larger or smaller than the largest and smallest tyre sizes listed on the car’s placard. Other specifications, such as load rating and speed rating, must also strictly adhere to the information on the placard, ensuring the car’s safety remains intact.
Tyres on the Same Axle
Another important regulation is that tyres fitted to the same axle must be of the same carcass construction and identical in size to the original tyres. The wheel track (the distance between the centreline of the opposing tyres on an axle) must also comply with specific standards, particularly when replacing or installing aftermarket wheels.
Aftermarket Wheels and Rims
The standards for aftermarket wheels and rims are particularly detailed, as modifications in this area can pose safety risks. For example, aftermarket wheels must have the same stud pattern and spacing as the factory-fitted wheels. Additionally, new spacers are not permitted to widen the wheels.
Sometimes, fitting different wheels and tyres may require adjustments to the brake calipers and brake discs to ensure proper fitment. However, modifications to these components are not allowed unless a specific engineering certificate is obtained.
The Importance of Compliance
These standards exist to ensure that passenger vehicles meet a minimum level of safety, even after the wheels and tyres are replaced. Adhering to these rules is crucial for maintaining the safety and performance of your vehicle.
Key Takeaway for Motorists
The most important thing for motorists is to pay attention to the tyre placard in their car, which is usually located in the glovebox or the driver’s door sill. If you’re ever unsure about what tyres you can or can’t fit, it’s always best to consult a tyre professional to ensure your vehicle remains compliant with Australian standards. They can also verify that any tyres they recommend meet size and wheel track requirements.
