Saturday, June 3, 2000
G O O D  M O T O R I N G  A N D  Y O U

The tyres that do not tire
By H. Kishie Singh

ONE of the greatest inventions that has contributed to the advancement of the automobile is the pneumatic tyre. The early cars, which were obviously called "horseless carriages"were just that. The seating arrangements remained the same; only an engine had been added. Often the driver sat outside the passenger compartment. Most important, the wheels remained as they were: solid , with wooden spokes that transmitted every bone-rattling shock to the passenger.

Along came the shock absorber. And it did just that.The favoured type was a series of steel strips cambered to form a bow, facing upwards. The carriage was placed on top. The weight of the carriage on the steel strips, bent them slightly and this stored energy in the steel . While moving over uneven ground, they provided a springy ride for the passenger. It was a improvement over the rigid construction which threw the passenger from side to side and made high speed impossible. The hydraulic shock absorber came next. The gas-filled shock absorber is a recent invention.

Long before all this happened, the search for the ideal tyre was foremost on automobile manufacturers’ mind. Research in France by Mchelin led to the ‘word’ ‘pneumatic’. The French word for tyre is pneu (pronounced P New), derived from ‘pneumatic’. The wooden wheel evolved to steel spokes or pressed steel and the solid rubber rim was replaced by tyres and tubes. They allowed the trapped air to form a cushion of air. The car rode on a cushion of air. What could be smoother?

  Suddenly rubber was in great demand. Charles Goodyear of the USA, a well-known name making wheels, went to Malaya and bought up vast rubber plantations.

Rubber would be hard to replace as the basic requirement for tyre and tube. Butyl is a preferred material for tubes but rubber is basic. Similarly in tyres there have been steel belts added, rayon, nylon. These are additional compounds, but the basic compound has always been rubber. Then came the radial tyres main advantage was that it was perfectly round an improvement over the old brass-belted tyres. A car with radial tyres riding on a cushion of air provided the ultimate smooth ride.But the search continued for a better wheel.

What lets the tyre down is the extreme heat generated by friction caused as the tyre rushes over tarmac, going around corners, accelerating and while braking. There is also vibration, and noise is generated. So a wheel (rim plus tyre plus tube)has to absorb the vibration and avoid generating noise.

A great leap forward was the tubeless tyre. Prior to this, air was contained in a tube which was fragile so it was contained in a tyre for protection. One immediate advantage was that the tyre ran cooler. The constant shuffling of the tube inside the tyre caused friction and generated heat. No tube, less heat a tubeless tyre is less prone to overheat.

So we had a tyre that held the air, was radial weighed less, lasted longer, and as an added value, because of a combination of the above, offered less rolling resistance, the immediate effect less fuel consumption, more mileage to the litre.

There is a safety angle to a tubeless tyre . It deflates a lot slower than a tube tyre which can deflate suddenly. It is fairly simple to fix a tubeless tyre, but it requires special tools and things like sealant, rubber plugs.

The search for excellence continues to make life more fun for the motorist.