Patent ID: 6412532
Filing Date: 2002-07-02
Classification: B29D,B60C,Y02T

Abstract:
A pneumatic tire for an automobile in which two layers of belt layers including a first belt layer on a side of the carcass layer and a second belt layer on an outer peripheral side thereof are arranged on an outer peripheral side of the carcass layer in a tread portion and the tread portion comprises a two-layered structure of a cap tread layer and an under tread layer:wherein the under tread layer comprises: a center region defined by a range of 30 through 70% of a width of the first belt layer centering on a tire equator and a range of 0.5 through 2.0 mm as a center region thickness T1 in a tire diameter direction from the second belt layer; and shoulder regions each of which are defined by a region between the center region and an outer side, a range of 1.0 through 5.0 mm as a shoulder region thickness T2 thereof and a distance between an end portion of the first belt layer and the outer side being 30 mm at a maximum, said center region and said shoulder regions comprising rubber composition members different from each other; wherein the center region is arranged with a rubber layer having a blending system in which JIS-A hardness falls in a range of 65 through 80 and an amount of blending a softening agent relative to rubber 100 weight parts is smaller than a blending amount thereof of the cap tread layer by 10 weight parts or higher, the shoulder region is arranged with a rubber layer having a blending system in which the JIS-A hardness falls in a range of 50 through 70 and an amount of blending a softening agent relative to the rubber 100 weight parts is smaller than the blending amount of the cap tread layer by 10 weight parts or higher and a ratio (tan &dgr;2/tan &dgr;1) of loss tangent (tan &dgr;2) of the rubber layer of the shoulder regions to loss tangent (tan &dgr;1) of the rubber layer of the center region is &frac23; or lower, and wherein the shoulder region thickness T2 is larger than the center region thickness T1.