
21 Tyres, road wheels and hubs
21.1 TYRE CONSTRUCTION Basic tyre construction
Tubed and tubeless tyres
The separate rubber inner tube acting as a flexible bag
to retain air introduced under pressure early became an
established feature of pneumatic tyre construction. It
comprises an endless tube slightly smaller than the
inside of the tyre
itself,
its only opening being an
inflation valve projecting through the wheel rim. Inner
tubes were originally made from high-quality natural
rubber, but this has long since been superseded by a
certain type of synthetic rubber able to retain air much
better.
Since the mid 1950s it has become established