CROSS 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. 

Roy et al. [11] carried out vacuum pyrolysis of used tyres, with a bench-scale reactor and with cross-ply tyres as feedstock. When the pyrolysis of rubber is carried out under vacuum the spectrum of quality products obtained is distinct from the usual atmospheric... 

Fig. 11.1 Schematic depiction of the textile ply structures in (a) a bias- or cross-ply tyre ...

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. 

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 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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