Pneumatic tire for front wheel of motorcycle

Abstract

A pneumatic tire for a front wheel of a motorcycle comprises a pair of bead cores, a radial carcass toroidally extending between the pair of bead portions, a belt disposed on a radially outer surface of the carcass, and a tread portion disposed thereon, wherein the carcass is comprised of at least one carcass ply containing organic fiber cords, and the belt is a spiral belt layer formed by spirally winding a continuous rubberized cord or a continuous ribbon-shaped body containing plural cords therein in a widthwise direction of the tire, and the tread portion has a two-layer structure comprised of a cap rubber layer and a base rubber layer in at least a central region in the widthwise direction of the tire, or a reinforcing layer is disposed inside an innermost carcass ply or on an inner surface of an innerliner, or the bead core is a helically wound laminate of a single steel wire having a polygonal shape at a section of the bead core in the radial direction.

Description

[0001] 1. Field of the Invention[0002] This invention relates to pneumatic tires for motorcycles, and more particularly to a pneumatic tire for a front wheel of a motorcycle capable of preventing the occurrence of shimmy in the high-speed running to improve a steering stability, particularly straight running stability.[0003] 2. Description of Related Art[0004] In the pneumatic tire particularly mounted onto a front wheel of a motorcycle, the steering performances such as handling and the like are considered to be important, so that it is usual to adopt a belt comprised of at least two belt layers, cords of which belt layers being crossed with each other, or so-called cross structure belt up to the present time.[0005] With the recent advancement of weight reduction and higher performances in a vehicle, a micro-oscillation of a handle or so-called shimmy phenomenon is actualized in the motorcycle. Particularly, it is strongly demanded to prevent the occurrence of shimmy at a high freq...

AI Technical Summary

Benefits of technology

[0009] The inventor has noticed that the tire having the spiral structure belt has characteristics that the tread portion is flexible, the change of ground contact shape in the high speed running is less, the high speed stability is excellent and the like as compared with the conventional cross structure belt and made various studies in order to solve the problem of degrading the steering performances due to the low bending rigidity in the ground contacting region when such a tire is applied to the front wheel of the motorcycle and as a result, the invention has been accomplished.

Problems solved by technology

However, the tire having the above cross structure belt is difficult to flexibly absorb the pushing up of micro-irregularities on the road to the tread surface of the tire and the micro-oscillation of the handle resulted therefrom.

In the above pneumatic tire for the motorcycle, however, the pushing quantity of a central portion of the tread becomes large with the increase of the speed to decrease the ground contacting area of the tread, which causes the lowering of the stability in the high speed running.

However, when the tire having the above spiral structure belt is used in the front wheel of the motorcycle taking count of steering performances such as steering stability and the like, since the cord in the belt extends substantially in the circumferential direction of the tire, the bending rigidity of the tread portion in the widthwise direction thereof is too low as compared with the cross structure belt, and hence the handle response, gripping force on road surface and the like are largely lacking and the steering performances are degraded.

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