Tyre care

Some users get exceptional distances out of their tyres. How? They look after them.

Tyre pressure

• A 20 percent drop in pressure (from 26psi to 21psi) increases the rate of wear by 20 percent. Severe over-inflation also causes wear, but a 10 percent increase has a very small effect.
• The AA found that tyres under-inflated by around 20 percent increased a car's fuel consumption by 8 percent.
• As well as wearing faster and using more fuel, soft (under-inflated) tyres have an unstable hold on the road. And if your tyre pressures are uneven (with different levels of inflation), you could end up out of control on a corner.
• Keep the pressures at the manufacturer's recommended levels, and remember to adjust upwards for heavy loads or prolonged high-speed driving. You should be able to find the manufacturer's recommendations in your car's handbook, or on a sticker that's often on or near the driver's door. Otherwise, ask your car dealer or a tyre company what the recommended levels are.
• Buy your own gauge. Petrol station gauges are often inaccurate. And don't forget to check the spare.

Run straight

• Have the wheels balanced and aligned when you fit new tyres.
• Have the alignment checked if you have a severe impact with a kerb or very large pothole or rock, or notice wear and/or feathering of the edges when you check your tyre pressures.

Steady does it

• Go gently through bends and avoid heavy braking.

 

Rotate

• It's normal for front-wheel-drive cars to wear the front tyres more rapidly. Rotate the tyres every 10,000km to even out the wear. The legal minimum is 1.5mm in all principal grooves around the circumference of the tyre (it used to be 1.5mm of tread over 75 percent of the tyre). The tread wear indicators will guide you, or you can use a tread-depth gauge (pictured, right) to keep track. They cost around $10. Tyre dealers usually do free checks. 
• If your tyres are wearing rapidly or unevenly, or if the steering pulls to the side, have the wheel balance and alignment checked (cost: usually around $60).

Given good operating conditions, regular rotation and a conservative driving style, a set of new premium steel-belt radials should last for 50,000km or more. Expect less from around-town use with lots of turning and braking, or high-speed use with hard cornering and braking. 

Which last longest?

We're often asked which tyres last longest. We don't test for tyre wear, because of cost. And there are no other reliable indicators - some tyres have a tread-wear rating on their sidewalls, but local tyre-makers say the ratings often have little relevance to New Zealand conditions.

And long-lasting tyres may not be a good thing. The US consumer organisation Consumer Reports says tyres that last too long may pose a safety risk, because rubber-compounds deteriorate with age. Some major car manufacturers have recommended throwing away tyres after 6 years, regardless of wear.

Tyres are usually date-coded, so a tyre dealer can work out if a tyre is really old. In New Zealand tyre wear is fairly rapid, so 6-year-old tyres aren't common - except for imported second-hand tyres. If long life is your priority, ask your tyre dealer for a model with a good tread life. Just be aware that long tread-life and good grip don't always go together.

How to buy

To get the most even performance, it's best to replace car tyres as a set. But if cost or convenience reasons make this unrealistic, there are some simple rules.

• Replace a single tyre with the same type and size (a different brand is acceptable in an emergency). Don't mix an old cross-ply type with a radial, or a steel belt with a fabric-belt tyre on the same vehicle. This can make the vehicle too difficult to handle safely and is against the law.
• Put the tyres with the best grip on the rear.
• If you change from one tyre or size to another, change at least both the tyres on the axle. The WOF rules say you can fit tyres that are no more than five percent larger or smaller in diameter. If they are wider, the tread must not extend outside the body panels and the vehicle's track must not vary by more than 25mm. Anything bigger in diameter or wider will require a modified certificate. 
• Phone around. Ask about the price difference between budget and premium tyres, and about extra benefits like road hazard warranties.

We found large variations in tyre prices. Retailers running specials were able to sell some models around $100 cheaper per tyre than others. So make sure you shop around as you could save a fortune.