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 The
wheel, as we know, has travelled a long way since the Sumerians invented
it 5000 years ago. However, the pneumatic tyre of today invented 150 years
ago is far younger. Robert William Thomson was granted his patent for
an 'air tube device', the forerunner of the modern pneumatic tyre, in
1845. It gained popularity with its re-invention some 40 years later when
John Boyd Dunlop first produced and commercially used this concept on
bicycles. One should admire the vision of these pioneers as both Thomson
and Dunlop targeted their invention primarily towards reduction of fatigue
and physical discomfort caused by the jarring, vibrations and high noise
levels while travelling on solid tyres.
Though tyres have come a long way with remarkable improvements so that
they can operate more efficiently at high speeds for sustained periods
under loads on wet and dry conditions, all with remarkable safety, the
basic concept of the pioneers has still remained the same.
A pneumatic tyre can be described as a "toroidal shaped, flexible,
high performance composite membrane capable of containing air or fluid
under pressure when mounted on a suitable rim." That sounds like
quite a mouthful but what it means in essence is that there are certain
basic requirements which remain unchanged in any tyre. There are other
features which differ depending on the conditions they operate under.
Thus a passenger car tyre varies from a truck or light commercial vehicle
tyre.
Since a pneumatic tyre has to face road shocks, the first requirement
is the ability to absorb these shocks while cushioning and providing a
comfortable ride. Next comes its ability to carry load at its required
pressure. It has to transmit engine torque to put the vehicle in motion,
while effectively also deal with the braking torque to stop the same.
It has to develop adequate cornering force to counter the centrifugal
force and other lateral forces like wind force and yet remain stable while
negotiating curves, combined with excellent grip. Often these requirements
are conflicting which is why meeting these objectives is a challenge for
tyre engineers.
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May 2002
