Pneumatic tire having outer tread layer of foam rubber

A pneumatic tire having a tread portion formed with a plurality of circumferential grooves, a plurality of lateral grooves extending in the tread crossing direction at least between one of the circumferential grooves and each axial end of the tread and arranged at substantially regular intervals in a circumferential direction of the tire, land portions partitioned by the circumferential and lateral grooves, and said tread portion composed of at least two rubber layers with a radially outward arranged outer rubber layer and a radially inward arranged inner rubber layer, relatively thin side rubbers having anti-bending and anti-cutting performance for covering both axial ends of the tread portion composed of said outer and inner rubbers layers, said land portions in the tread portions having sipes, wherein the Shore A hardness of said inner rubber layer is in the range from 54 to 80 degrees and is higher than that of said outer rubber layer;

• said outer rubber layer is made of foam rubber whose foam rate lies from 5 to 50% and whose volume ratio with respect to a volume of said tread is at least 10%;
• each of said thin side rubbers made of rubber including no foaming agent and extends from the axial end of the tread into said lateral grooves to cover lateral groove bottoms formed on said outer rubber layer;
• the portions of said outer rubber layer covered by said side rubbers at said groove bottoms of lateral grooves formed into a wedge-shaped and said wedge-shaped portions of the outer rubber layer have a decreased foam rate;
• and said sipes formed in the land portions of the tread extend in groove depth direction into said relatively hard inner rubber layer through said foam outer rubber layer.