Page:The Cycle Industry (1921).djvu/71

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it was a glorified hose pipe but thinner in the walls. It was repaired with rubber plugs which were inserted from the outside, and although a very lively fast tyre, it went out of vogue because of the difficulty of making satisfactory repairs. The U.S.A. makers supplied nothing but this type of pneumatic tyre for several years.

The Constrictor racing tyre is so constructed in the wall that the cover can be peeled back away from the fabric, allowing withdrawal of the inner tube and repair on the outside of the tube. Tyres of this description are only favoured by racing cyclists on account of the expert knowledge required to make a proper repair. It is, however, of interest to note that a "speedman" finds it an advantage to carry a spare tyre of this description in preference to using a thicker and heavier type, which requires longer to repair, than to change one of the lighter, thinner kind. The secret of the extra speed lies in the fact that a thin walled tyre is more resilient than a thick one, and when suitably inflated the rapid expansion of the tread, previously compressed by the rider's weight, does not retard the propulsion of the machine so much as a thicker one. A technical explanation of the why and wherefore of this must be sought in theoretical treatises on pneumatic tyres.