Tyres barely rate a second thought for many motorists, until one goes flat or they need to be replaced.
However, given a little care and attention, tyre life can be maximized and overall vehicle performance, fuel consumption, occupant safety and comfort can all be improved. Here are a few tips to help you achieve this, as well as some background information that will help you select the right tyres for your car when it comes time to replace them.
General tyre questions
How long should tyres last?
Too many factors affect tread wear rates to allow an accurate answer to this question.
Some, such as “enthusiastic” driving styles, high speed operation and cornering, harsh braking and hard acceleration will be influenced by the driver. But factors like road surface, climatic conditions and tyre and vehicle design aren’t.
When is a tyre worn out?
- The law requires a minimum of 1.5 mm of tread across the face of the tyre normally in contact with the road.
- To help gauge this, car tyres have tread wear indicator bars moulded across the tread at regular intervals around the tyre.
- The tread is at its legal limit when the wear bar is level with the tread blocks.
- This is the minimum legal tread requirement, but the tyre should be replaced well before it gets to this point as wet weather performance will diminish.
Remember also that cuts or other damage can render a tyre unroadworthy too.
Can a tyre be too old?
- There is no law that specifies when a tyre is too old for further use.
- A tyre’s serviceability is determined by its condition, not its age.
- Some industry experts suggest that worn out or not, a tyre may have passed its useful life after about five years, however this is not recognized in law.
- A tyre can deteriorate, even if it’s been sitting unused in the spare wheel well.
- A production date code is usually moulded into the tyre sidewall. Consult a reputable tyre dealer for further advice on interpreting this code.
Choosing replacement tyres
What’s the best brand of tyre?
This depends largely by what yard-stick you measure “best”. For one person the cheapest, longest lasting tyre will be the best. To another, the tyre that offers the most grip is the best, even if it has a fairly short life.
Tyre engineering is about compromises and trade-offs. It simply isn’t possible to design a tyre to do everything well. High performance tyres that offer high levels of grip are often quite soft and can have a short life, while long wearing tyres may have less grip. Similarly, tyres that have chunky tread patterns to displace water can provide high levels of wet grip but are often noisy.
Ultimately you’ll need to consider what’s important to you and discuss your needs with a reputable tyre dealer. As a general rule though, if you stick to the well-known mainstream brands, you shouldn’t go too far wrong.
For safety’s sake, remember you usually don’t get anything more than what you pay for.
Original equipment Vs replacement tyres
Increasingly, vehicle and tyre manufacturers work together to design a complete vehicle / tyre package that provides the driving and handling characteristics the vehicle manufacturer is trying to achieve. With the tyre being such an integral part of the vehicle it would be sensible, where possible, to stick with the make and model of tyre the vehicle was fitted with when new.
Original equipment tyres also often have tighter manufacturing tolerances than replacement tyres and some vehicle manufacturers offer OE standard tyres through their service outlets.
What size tyres are right for my car?
The recommended tyre sizes, speed, and load ratings are printed in the owner’s handbook and are shown on the tyre placard fitted to the vehicle.
Replacement tyres must have a load rating at least equal to that specified by the car’s maker. There is some latitude allowed for speed ratings, but we recommend fitting tyres with a minimum speed rating at least equal to that shown on the vehicle's tyre placard. The minimum legally acceptable speed rating is 180km/h.
Caring for your tyres
Correct inflation pressures are essential if your tyres are to deliver maximum life and performance.
- Under-inflation causes excessive tyre flexing and heat build-up and is the number one reason behind catastrophic tyre failure or “blow-outs”.
- Under inflation also causes accelerated tyre wear rates, uneven wear patterns, heavy steering and increased fuel consumption.
- Over-inflation can result in a harsh ride, uneven wear patterns and increased risk of tyre impact damage.
- Incorrect inflation pressures will also reduce the all-important tyre “footprint” on the road, resulting in impaired handling and braking.
Some tyre dealers promote nitrogen for tyre inflation.
Determining the correct pressure
All vehicles built since 1973 have been fitted with a tyre placard that lists the specifications of the original tyres fitted to the vehicle and the correct inflation pressures. The information will be in the owner’s handbook as well. The diagram below shows an example of a tyre placard.
- The placard pressures are the minimum allowable cold pressures.
- They will be shown in Kilopascals (kPa) and often in pounds per square Inch (PSI) as well. Conversion: 7kPa = 1 PSI
- For increased load carrying or sustained high speed driving (around 100km/h for more than 1 hour) tyre pressures should be increased as advised on the placard or, as recommended by a reputable tyre dealer.
- It’s acceptable to keep tyres inflated to the high load / speed pressure if you wish.
- Tyre pressures should be checked cold as they increase as the tyre heats up from driving.
- Don’t bleed air from hot tyres to obtain the recommended cold pressure.
- It’s not a bad idea to have your own tyre gauge for doing your regular (at least once a fortnight) pressure checks – and don’t forget the spare.
- If you notice any significant pressure drop, especially on just one tyre, have the cause checked out – you might have a puncture or defective valve.
- Remember to replace the valve dust caps after checking tyre pressures.
- They help seal air into the tyre and exclude dirt which may cause the valve to leak.
Wheel alignment, wheel balance and tyre rotation
Worn steering and suspension components and incorrect wheel alignment
and balance all influence how long a tyre lasts so it’s a good idea to watch for the development of uneven tread wear patterns while checking tyre pressures. If you notice any problems, have your mechanic check further.
For most cars, regular tyre rotation
and balance is also recommended to achieve best tyre life.
Understanding tyre markings
To many, the markings on tyre sidewalls may appear to be confusing. However, once you know the code they are in fact quite useful. The following information relates to a typical passenger car radial tyre.
– The brand, make and model of the tyre.
– Section width
These three numerals show the section width of the tyre in millimetres. The section width is the total inflated width at its widest point (excluding sidewall ribs and lettering) – the next diagram will make this clearer. In some cases the letter "P" will precede the numerals – this is a minor marking system variation and just indicates the tyre is for a passenger car.
– Aspect ratio
The second number is the aspect ratio or profile of the tyre. This number tells you about the section height of the tyre, by expressing it as a percentage of the section width. So in the case of a P205/60 tyre, the section width is 205mm, and the section height is 60% of that. The lower this number the lower the tyre’s profile. The aspect ratio for a passenger car is typically between 50 and 75. However, high performance cars may use tyres with aspect ratios as low as 30.
The single letter designates the type of tyre construction – R stands for radial.
– Rim diameter
This is the nominal rim diameter to which the tyre must be fitted. This measurement is always expressed in inches.
– Load index
This index number is checked against a chart to determine the maximum load, in kilograms, the tyre can carry at the speed indicated by its speed symbol.
– Speed rating
This symbol is also decoded by referring to a chart to determine the maximum speed to which the tyre has been safely tested. Passenger car tyre speed ratings start at N (140km/h) and go through to Y (300km/h).
Punctures in tubeless tyres must only be repaired by fitting a vulcanized plug or patch from the inside of the tyre. In all cases the tyre must be removed from the rim to check for internal damage. Plugs that are fitted from the outside do not provide a permanent repair. Tyre repairs are only allowed in the tread area and are best performed by a reputable tyre dealer.
Tyre sealants definitely do not provide a permanent repair. Even those supplied with vehicles as original equipment are only intended to seal small punctures to allow it to be driven carefully to a repairer to have the tyre repaired or replaced.
Be cautious of sealant products that are put into tyres as a precaution to prevent flat tyres by sealing punctures as they occur. Even if they do work as claimed, there is a very real risk that they can mask a tyre that is potentially dangerous to keep using.
Other types of tyres
Retread tyres were once a commonly available, low cost option to new tyres. However, as the price of new passenger car tyres has gradually decreased, so has demand for retreads. However, trucks and heavy vehicles are still major users of retreaded tyres because of the high cost of new tyres for these vehicles.
Run flat tyres
Run flat tyres are covered in our temporary use
spare tyre fact sheet.
Low rolling resistance tyres
An increasing number of vehicle manufacturers are fitting low rolling resistance (LRR) tyres to their ‘green’ models. These tyres claim to reduce fuel consumption by 2 to 3 percent. They are available from a number of tyre manufacturers as in-service replacements for original equipment LRR tyres, but increasingly, tyre manufacturers are expanding their ranges to service vehicles that were not originally fitted with them. If you have a vehicle that was originally fitted with LRR tyres it will be necessary to replace them with like tyres if you want to maintain the fuel saving benefits they provide.
It’s common to see vehicles fitted with a mixture of two or more brands of tyre. While this is permitted under Queensland law, it is highly undesirable and should be actively discouraged. Mixing different brand tyres, even if they are of the same size and construction, can dramatically alter the handling characteristics of a vehicle. For safety sake only fit matching tyres.
Spare wheels and tyres
At one time a vehicle’s spare wheel was identical to and completely interchangeable with those on the road. However, vehicle manufacturers are increasingly supplying spare wheels that are different in appearance and size to those on the road. And some vehicles don’t even have a spare wheel.
For more information see our related fact sheet
Our thanks to the Australian Tyre Manufacturers' Association for providing illustrations for use in this Fact Sheet.
Should you require further assistance please contact our Motoring Advice Service or email us your details now.