Pneumatic tire for automobile and its fabrication method

摘要

A pneumatic tire for an automobile having a tread portion (4) in a two-layered structure of a cap tread layer (4a) and an under tread layer (4b), in which the under tread layer is constituted by a center region defined by a range of 30 through 70% of a width of a first belt layer and up to 0.5 through 2.0mm in a tire diameter direction from a second belt layer and a shoulder region extended from both end portions of the first belt layer continuously from the center region to an outer side by 30mm at maximum on one side and having a thickness of 1.0 through 5.0mm, the regions comprising rubber composition members different from each other, the center region is arranged with a rubber layer where 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 that of the cap tread layer by 10 weight parts or more, the shoulder region is arranged with a rubber layer where JIS-A hardness falls in a range of 50 through 70 and the amount of blending the softening agent relative to rubber 100 weight parts is smaller than that of the cap tread layer by 10 weight parts or more and a ratio (tan delta 2/tan delta 1) of loss tangent (tan delta 2) of the rubber layer of the shoulder region to loss tangent (tan delta 1) of the rubber layer of the center region is 2/3 or smaller.