Tires in which a performance on a snow and ice road and a wet road is improved include winter tires. In some winter tires, various fillers are mixed so that an edge effect for an ice surface is obtained, and foam rubber is used so that a water absorption edge effect by means of a foam layer during the service period is obtained.
However, in general, when rubber is vulcanized and hardened, the filler and the foam layer are not exposed on a tire surface which directly contacts with a mold, and thus a membrane tends to be formed on the tire surface. As a result, in the early stage of use of tire, the effects of the filler and the foam layer are not exerted (or the effects are small).
On the contrary, for example, Patent Document 1 and Patent Document 2 describe pneumatic tires for snow and ice road in which thin grooves are formed in a tread surface so that braking and driving performances in the initial wear stage are improved. Patent Document 3 describes a pneumatic tire in which shallow grooves which form an angle of 0° to 40° with respect to a tire circumferential direction are arranged at ground land sections of the treads in the tire width direction.
Patent Document 1: Japanese Patent Application Laid-Open No. 2004-34902
Patent Document 2: Japanese Patent Application Laid-Open No. 2004-34903
Patent Document 3: Japanese Patent Application Laid-Open No. 7-186633
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