All you need to know about your tyres – or is it?
We get asked many questions about tyres. These are the 10 most common, with the answers you need.
1. My tyre placard mentions particular tyres and rims. Can I fit different to this?
Yes, you can; but the tyre/rim combination and width/diameter must meet certain requirements. The amount that the width and diameter may change by depends upon the type of vehicle. There are different rules for 4WDs, passenger vehicles, etc. You can learn more by reading the Minor Modifications publication (PDF, 414 KB).
2. Can I increase my vehicle’s ride height?
There are various ways that you could increase the ride height of your vehicle. These include by increasing your vehicle’s tyre dimension, lifting its suspension, or by using body blocks. The amount you can raise it depends on which methods or combination of methods you use to do so. The most that you can raise your ride height by for each single method is:
- 50mm by increasing the tyre dimension
- 75mm if raising by lifting the suspension
- 50mm by using body blocks
However, if you are using a combination of these methods, the most your vehicle can be raised is 150mm.
Just to complicate things a little more, these limits are not applicable to all vehicles. They are a good guideline, but for the exact raise you can make to your vehicle you should examine the National Code of Practice for Light Vehicle Construction and Modification (PDF, 1.93 MB).
3. Can I use low-profile tyres with a wider diameter on my vehicle?
This is possible to do, but you must make sure that the overall diameter, load rating and speed rating comply with legal requirements. Often, low-profile tyres will be fitted to larger diameter rims; this maintains the overall diameter to requirements. Once more, you should refer to the National Code of Practice for Light Vehicle Construction and Modification (PDF, 1.93 MB).
4. What is the maximum tyre diameter increases and decreases I can make to my 4WD?
With some 4WD vehicles, you may increase tyre diameter by up to 50mm and decrease it by up to 26mm, from the vehicle manufacturer’s recommended diameter. These are:
- 4WD passenger vehicles specifically designed for off-road use
- 4WD goods vehicles and their 2WD equivalents, if the chassis and running gear are essentially the same as the 4WD versions
However, all-wheel drive vehicles (AWDs) are not included in these. The Minor Modifications publication (PDF, 414 KB) provides the information you need.
5. Can I lower the speed rating of my tyres?
You may want to lower the speed rating of your tyres, and this is possible, providing the tyres meet certain minimums. These are:
- 140km/h for off-road passenger vehicles
- 180km/h for other cars or car derivatives carrying up to nine adult passengers in seated positions
- 120 km/h for other motor vehicles
There is an exception to all these rules: if your vehicle has a lower top speed than the above, then the tyre may not have a speed rating above the vehicle’s top speed.
6. Can I fit different brand tyres to the same axle?
Yes, though it is preferable to fit the same brand. However, what you cannot do is fit tyres with different construction (e.g. cross-ply, steel radials, textile radials, etc.).
We also recommend that tread patterns should be the same on tyres fitted on the same axle, though there is no legal requirement to do so.
7. How often should I change my tyres?
Tyres last far longer today than they used to. However, when they need changing depends on many factors, such as:
- The type of road surface on which they are driven
- The wear and tear suffered
- The kilometres covered by the tyre
- Irrespective of any of the above, the age of the tyre
Most tyres will last between 60,000 and 80,000 kilometres. However, manufacturers recommend that tyres should be changed every five years at a minimum, due to age degradation of the rubber.
8. How often should I check my tyres?
We recommend that you carry out four tyre safety checks at least once per month, and more often if you drive every day. If you are making a long journey, you should also carry these checks out. These four essential checks are:
- Tyre pressure
- Condition of the tyre wall
- Tread depth
- All the above on the spare
9. Should I change all four tyres are the same time?
If you rotate your tyres, the wear and tear on them should be equal. If this is the case, you will probably need to change all four tyres at the same time. However, if not all four tyres need to be changed it is always best to change the tyres on the same axle simultaneously. This will ensure that handling and grip is uniform on the same axle, which will improve your safety on the road.
10. What is the danger of driving on worn tyres?
If you drive on worn tyres, you could be given a hefty fine. However, this should not be your main concern. Worn tyres provide less grip and traction. Your handling will be worse, and your braking distances will be longer. Worn tyres are a big contributor to road accidents and fatalities in Australia.
Do you have a question about your tyres? Are you unsure whether they are legal or if they should be changed? For the answers to all your tyre questions, contact Darra Tyres.
Keeping your family and fleet safe on the road,