BIAS TYRE

NR usage in modern radial tyres has substantially increased. The amount of NR used is about 21 kg per tyre for a radial construction compared with about 9 kg in a bias truck tyre. Bernard and coworkers have compared the NR levels of heavy-duty radial truck tyres to those of the equivalent bias tyre and noted the following increase " ... 

A typical formulation for a bias tyre truck tread is shown in Table 36. 

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. 

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. 

Rubber coated fabric is cut to give a bias to the fabric on its application to the tyre carcass. The knife angle can be adjusted in the cutting machine. 

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... 

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

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 ... 

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. 

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