Tire, device for extruding unvulcanized tread rubber for the tire, and method of extruding unvulcanized tread rubber for the tire

摘要

A crack suppressing rubber, which has elongation-at-break which is superior to elongation-at-break of a cap rubber, is disposed so as to reinforce a vicinity of a groove bottom of a circumferential direction narrow groove provided in the vicinity of a shoulder of a tire tread. Due to this, generation of cracks from the vicinity of the groove bottom, at a time when land portions at an outer side of the circumferential direction narrow groove are greatly deformed due to a large lateral force or due to recesses and projections of a road surface or the like, and growth of generated cracks are suppressed. As a result, breaking of land portions at outermost sides in a widthwise direction of a tire, and separation of the tread can be effectively suppressed. Namely, in accordance with the present invention, there is provided a tire which is suited to heavy-load vehicles and in which generation of cracks from groove bottoms of tread grooves (circumferential direction grooves in vicinities of shoulder portions, in particular) and growth of generated cracks can be suppressed.