The Truth About Tyres
Sydney Morning Herald
Saturday December 18, 1999
There are many misconceptions about tyres that we will try to correct in this two-part series.
Should you inflate tyres according to the pressure indicated on the tyre sidewall?
The tyre's maximum inflation pressure - not recommended tyre pressure - is moulded on the sidewall.
For normal operation, follow inflation pressure recommendations in the owner's manual or on the vehicle placard in the glove box or on the door post.
Tyres are built and rated to carry certain load capacities, and auto makers select those sizes compatible with the ride, handling, traction, fuel economy and load requirements of their vehicles. Vehicle manufacturers determine inflation pressures based on these requirements.
Is a tread pattern needed for great traction on dry roads?
Look at a typical racing tyre for dry conditions and you'll see it has no tread. This provides the ultimate in dry traction because of the maximum amount of rubber on the road.
A tread pattern, with its groove voids, actually impairs this adhesion capability on dry roads. Tyre tread acts as a squeegee on wet roads to remove water from under the tyre and channel it through the grooves for improved wet traction.
Would race tyres be the ideal street tyre for high-performance vehicles?
No. Race tyres are engineered for specific track surfaces and race vehicle suspensions. On a high-performance vehicle, race tyres would wear too quickly, provide an uncomfortable ride and deliver poor handling on wet or icy roadways.
But in many cases, the technology used at the racetrack is engineered into high-performance street tyres. For example, ultra-high-performance tyres employ a stiffer carcass and aggressive tread compounds to provide the performance attributes required for high-performance vehicles.
So performance tyres wear out faster because of the sticky tread compounds?
Performance tyres may wear out faster than conventional family car tyres; however, tread rubber polymers aren't the culprits. In fact, new polymers and ultra-tensile steel constructions are making performance tyres last longer than ever.
Performance tyres average about the same tread life as family car passenger tyres. Fast wear usually is due to high-horsepower vehicles fitted with the tyres and aggressive driving.
Is it true you should never rotate tyres from side to side, only front to back?
No. Radial tyres can be crossed from side to side in the rotation pattern. The old front-to-back rule applied to bias-ply tyres. (Note that some tyres are directional and the wheels can't be switched from one side of the car to the other.) Regular tyre rotation - say, every 10,000 km - promotes more uniform wear for all tyres on a vehicle.
Should you put new tyres on the drive-wheel position to get the most traction?
This is true only on a rear-wheel-drive vehicle. In all cases, install new tyres on the rear axle.
Most tyre buyers purchase new rubber for the drive-wheel position to get the most traction; however, by doing so, they transfer most of their traction capabilities from the rear and make it susceptible to oversteer. The vehicle's rear will fishtail and swing out in fast cornering or emergency manoeuvres.
© 1999 Sydney Morning Herald
