RADIAL PLY TYRE

Formerly termed braced tread, rigid breaker or belted tyre. A pneumatic tyre in which the cords of the casing plies run directly across the tyre section from bead to bead, and not at an angle as in a cross-ply tyre the breaker in a radial-ply tyre is an inextensible band which runs circumferentially round the tyre between tread and casing. It is made up of layers of bias cut fabric set at discrete angles to confer the required stability in the tread but maintain the flexibility in the sidewall. 

Typical butyl tube compounds for bias-ply and radial-ply tyres are shown in Tables 6 and 7. (Halobutyl tube compounds are described later.)... 

Bias-ply and radial-ply tyres require quite different inner tubes for optimum performance. Radial-ply tyres need ... 

Until the 1970s in Europe and the 1980s elsewhere tyres were built in cross-ply (diagonal ply) construction, with the reinforcement layer running at a bias to the direction of tyre rotation. Now the vast majority are radial ply with the carcass reinforcement layer placed radially, or at 90° to the direction of rotation. There is always an even number of plies or reinforcement layers - generally car tyres have two and trucks around 6 or 8 plies. In addition, there are tread reinforcing (bracing) layers called belts, which run around the circumference under the tread. 

The textile elements of tyres comprise reinforcing elements within the sidewalls and across the tread using continually developing structures which have come a long way from the CTOSS-ply or bias ply stractures of the post-war period in which fibre/fabric content could be as high as 21% (Fig. 11.1 (a)). Modem radial ply stmctures, on the... 

The apparent changes are small and tyres are still round and black with a hole in the middle—but a whole new technology has gone into the design, formulation and performance of the radial tyre as compared with the cross-ply. Machinery which was perfected for the high-volume cross-ply tyre production is not necessarily best for radial tyre making. 

Typical formulations and representative properties for heat resistant inner tube compounds intended for use in bias-ply and radial-ply truck tyres are shown in Tables 20 and 21. Crosslinked butyl is included in the radial tyre tube to provide green strength. Butyl reclaim could be used instead, for the same purpose. 

Other factors that affect the tyre behaviour and have a direct effect on both distribution and magnitude of applied pressure are the following type of tyre (radial or x-ply, high- or low-pressure tyre, etc.), surface and tyre condition (smooth or treaded, worn or new), temperature developed in the tyre, tyre resilience, type and condition of vehicle suspension and pavement surface irregularities. A detailed description of the effect of the above factors is beyond the scope of this book. 

The rubber industry is still adjusting itself to the worldwide acceptance of the radial tyre. This came much later in North America than in Europe and the repercussions of the advent of tyres of much greater longevity in this major rubber market has had an important influence on overall rubber usage. The different requirements of the radial tyre vis-d-vis the cross-ply have simultaneously increased the demand for natural rubber relative to SBR. 

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