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Sharp Drive Talk About Tyres & Suspension
Thursday 12 April 2018, 1:15PM
By Beckie Wright

The contact patch or footprint of the average car tyre is no bigger than an average man’s sports shoe. Those four footprints are the only thing keeping your car from hurtling off the road. Reduced grip at the contact patches increases crash risk and poor grip caused by a badly worn thread, low tyre pressure or a mismatched tyre will make the handling very unpredictable.

Incorrect pressures and reduced grip will cause longer stopping distances. Risk of skidding in corners and longer tyre wear can reduce tyre life. Improving your road handling grip can be as simple as checking your tyre pressures. Do it at least fortnightly. Weekly is even better. And while the tyres are cold, don’t forget the spare wheel. By the time the tyre looks soft, it is at least ten PSI too low and very dangerous. The more work a tyre does the more pressure it needs. Check the vehicle handbook to check the pressures for your load and speeds. Reset pressures before and after long trips.

The recommended pressure is the minimum safe pressure for cold tyres. Slightly higher pressures are acceptable and safe handling, but risk increases rapidly with any under inflation. Two or three PSI too low makes a big difference. Under inflated tyres are very dangerous. They aquaplane sooner, use more fuel, allow excessive sidewall flexing and roll off the rim. Under inflated tyres ultimately cause heat build-up, tread separation and blow-outs.

Highly over inflated tyres lack traction, skid easily, especially in the damp. While checking pressures, check the tyres for damage and uneven wear, the grooves maintain grip and by pumping water away from the tyres. At 100km an hour, that’s a bucketful, or rten litres per second per wheel. Low tread depth and speed in the wet cause aquaplaning and total loss of control.

The minimum safe tread depth is two milimeters and most tyres have treadwear indicators to show this. Tyres should always wear down evenly and if they don’t there is a problem that should be fixed. Uneven tyre wear can be caused by wrong tyre pressures, wheels out of alignment, or poor cornering technique.

The suspension is designed to exert firm downward pressure force on the contact patches for maximum grip and good ride comfort. It is crucial that every part is maintained. Hitting kerbs, potholes and similar incidents can affect the wheel alignment. At the first sign of the tyre shoulders rounding oe the tread blocks feathering, get the alignment checked.

Shock absorbers are crucial to maintaining grip and worn shock absorbers are dangerous. Harsh conditions and heavy loads or trailer pulling can weaken them so check them regularly. The smallest vibration or thumping from the rear while driving means there is probably unbalance. This causes excessive wear on the shock absorbers and and suspension. All the tyres should be identical and if that is not possible then they must be the same size and similar patterns. In matching identical pairs front and rear, always keep the better pair at the front.

Keeping your tyres and suspension well maintained not only ensures your safety but also saves fuel and reduces your carbon footprint, so for more information on advanced driver training NZ, approved advanced driving skills courses and corporate driver training please go to .    INDEX