Abstract: To prevent crack occurrence at groove bottoms on both side areas of foam rubber tread of all-season studless tires, the pneumatic tire having a tread surface portion composed of at least two outer and inner rubber layers is characterized in that the hardness of the inner rubber layer lies from 54 to 80 degrees in Shore hardness and is higher than that of the outer rubber layer, and further the outer rubber layer is made of foam rubber with a foam rate from 5 to 50% with at least 10% volume ratio with respect to tread volume. The outer foam rubber layer serves to improve tire performance on icy and snowy roads in winter, and the inner ordinary rubber layer serves to reduce change in groove width after vulcanization, that is, reduce dynamic strain concentration at lateral grooves and therefore to reduce crack generation at the lateral groove bottoms.

Abstract: To improve high speed durability or prevent tire ribs and/or blocks from being peeled off at high speed travel, a tread rubber member whose outer surface is formed into corrugation shape along tire axial direction, when seen in cross section, is prepared to form a green tire so that radially convex portions thereof may be located under tire circumferential grooves to be formed after vulcanization process and radially concave portions thereof may be located under tire ribs and/or blocks also to be formed after vulcanization process. Since the rubber flow rate of the tread rubber member under the circumferential grooves is relatively larger, when the green tire is vulcanized, the belt layers are conversely deformed into radially concave shape under the circumferential grooves.

Abstract: A heavy duty pneumatic radial tire includes a carcass consisting of at least one layer of metal cords substantially radially arranged, a breaker consisting of at least two layers of metal cords to form a main reinforcement with the carcass, and bead portions including hard and soft stiffeners. The carcass has a particular radial profile having a ratio of radii R/R' determined by a radius R' of a standard circle and a radius R determined by a particular definition and has a maximum distance f between an arc of the standard circle and the remaining carcass line smoothly extending from the profile curvature of the shoulder. Moreover a radial profile over a radially inner zone of the sidewall of 20-45% of the radial height SH has a curvature 1/.rho. less than 6.times.10.sup.-3 mm.sup.-1 at a location 32.5% of the radial height corresponding to a center of the profile.

Abstract: An apparatus for manufacturing a tire comprises a former for forming a carcass ply or the like to a cylindrical configuration, a bead holder for placing bead cores on the cylindrical carcass ply and then effecting assembly of a carcass ply-bead core structure. A drum receives the structure from the former and effects assembly of a cylindrical carcass layer and then deforms the latter into a trochoidal configuration to obtain a green tire. The carcass ply located between both the bead cores on the structure is caused to expand and the structure is placed on the drum, the bead cores are wrapped with the end portions of the carcass ply and then the green tire for the radial tire is assembled by attaching side wall members or the like.