TREADS, PNEUMATIC TIRES AND A PROCESS FOR IMPROVING TIRE PERFORMANCE

摘要

1318755 Tyre treads GOODYEAR TIRE & RUBBER CO 1 Oct 1970 [24 Oct 1969] 46687/70 Heading B7C A pneumatic tyre tread comprises two radially superposed vulcanized layers, i.e. a radially outermost positioned cap 11 and an underlying base 12, with either of the layers composed of 80 to 100 parts by weight of a copolymer of 1,3-butadiene and styrene and correspondingly 0-20 parts of another conventional elastomeric treadstock, and the other of the layers composed of 50 to 100 parts by weight of natural rubber or synthetic cis-1,4-polyisoprene having in excess of 80% of its polymerized units in a cis-1,4 configuration and correspondingly from 0 to 50 parts of another conventional elastomeric treadstock, with the radial depth of the cap being between 30 and 70% the depth of the cap and base which can be between 1À2 and 1/7 inches measured at the midcircumferential plane. The layers may be formed together from a common extruder head or be formed separately and adhered together. In another embodiment (Fig. 2, not shown) the cap 11 extends radially part way up the sidewalls 13 covering all of the base 12. In a method of use, the tyres are fitted to the front axle of a bus and when more than half the tread thickness of the cap has worn away the tyres are transferred to the rear axle, subsequent to regrooving if desired.