Pneumatic tire tread

An all season type pneumatic tire which is to be used throughout a year from a winter season through a summer season and comprises:

• a tread pattern formed in a tread portion divided into separated blocks at an outer surface of a tread rubber layer in at least a central region of said tread portion by a plurality of main grooves extending circumferentially and a large number of lateral grooves each extending toward a cross direction to each of said main grooves and having a shallower portion as compared with said main groove, said tread portion being a cap-base composite tread portion composed of an upper rubber layer forming a pattern of blocks and a lower rubber layer bordered on said upper rubber layer just therebeneath by a face connecting groove bottoms of said shallower portions of lateral grooves and forming a pattern of ribs separated from one another by said main grooves in the lateral direction and extending substantially continuously in the circumferential direction, and said upper rubber layer being substantially composed of a cap rubber having a JIS hardness at -20.degree. C. of not more than 75.degree. and said lower rubber layer being substantially composed of a base rubber having a JIS hardness at 100.degree. C. of not less than 54.degree. and a loss tangent of not more than 0.22 at 50 Hz, 25.degree. C. and a strain of 2%.