Bridgestone Corporation

Katsutoshi Tani

Misao Kawabata

Hisao Ushikubo

Yutaka Yamaguchi

Hiroo Matsunaga

A pneumatic radial tire comprises a radial carcass of at least one carcass ply, a belt and a tread successively arranged on the carcass outward from the crown portion in radial direction, in which the tread has a plurality of circumferential grooves extending circumferentially of the tire and a plurality of island portions defined by these circumferential grooves and both side ends of the tread. The belt is comprised of at least two main belt layers and an auxiliary belt layer of a specific structure formed by helically and continuously winding a ribbon-shaped ply in series.

Pneumatic radial tire including a wound auxiliary belt layer

A high-speed running pneumatic radial tire comprises a cylindrical crown portion, a pair of sidewall portions extending inward therefrom, a radial carcass extending from one of the sidewall portions through the crown portion to the other sidewall portion, and a belt and a tread successively superimposed on the crown portion outward in the radial direction of the tire. The tread has plural rows of blocks defined by plural circumferential grooves and many lateral grooves, and the belt is comprised of at least two main crosscord belt layers and an auxiliary belt layer arranged thereon. The auxiliary belt layer is formed by spirally winding a rubberized ribbon ply of heat-shrinkable cords on the main belt layers, in which an overlapped amount of the ribbon ply is made large in a zone of the tread substantially corresponding to the block row than in a zone of the tread substantially corresponding to the circumferential groove.

Pneumatic radial tires for passenger cars

A high performance pneumatic radial tire comprises a toroidal carcass, a tread radially outside a crown portion of the carcass, a belt layer interposed between the carcass and the tread and having a same width of the tread, and an auxiliary layer arranged between the belt layer and the tread and covering the entire belt layer. organic cords are buried substantially parallel to an equatorial plane of the tire in the auxiliary layer, and land portions are defined between at least two circumferential main grooves formed in an outer surface portion of the tread and between the circumferential main grooves and axially opposite edges of the tread. In the tire, a rigidity of the tire corresponding to locations overlapping the circumferential main grooves is made smaller than that of portions corresponding to the land portions by, for example, constituting the auxiliary layer from at least two auxiliary plies comprising one auxiliary ply located on a radially innermost side and covering the belt layer over an entire width thereof, and cutting at least a radially outermost auxiliary ply at locations overlapping the circumferential main grooves among the auxiliary plies having portions overlapping the circumferential main groove.

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Kodaira, Japan

Katsutoshi Tani