Abstract: A pneumatic tire comprises a tread portion provided with sipes, the sipes each having a zigzag configuration at any depth from the top of the sipe to a certain depth, and the zigzag configuration having vertexes Q1 on one side of the zigzag and vertexes Q2 on the other side of the zigzag, wherein as the depth increases from the top of the sipe to said certain depth, the vertexes Q1 shift in the longitudinal direction of the sipe and the direction of the shift is turned at least once such that the vertexes Q1 first shift towards one direction then towards the other direction, thereby describing a zigzag line extending from the top of the sipe to said certain depth and having at least one tuning point, but the vertexes Q2 describe lines which are linear or less zigzag when compared with the zigzag lines described by the vertexes Q1.

Abstract: It is an object of the present invention to improve the running performance on snowy and icy roads, and for this purpose, blocks provided with sipes are formed at a tread portion. The sipes include an open top end that opens at a block surface and a bottom, and a configuration of the sipes in a plane parallel with the block surface comprises a zigzag part extending in the length direction of the sipes. The zigzag part displaces upon turning back to one side and to the other side in a length direction of the sipes in the course from the open top end to the bottom. At least one block includes a first sipe and a second sipe which depths of the turn-back points of displacement from the open top end and/or positions of the turn-back points of displacement in the length direction differ from each other.

Abstract: A cavity face 34 of a mold 32 has a protruding ridge P. A shape of cross section of the ridge P is almost rectangular. The ridge P has a first corner P1, a second corner P2, a third corner P3 and a fourth corner P4. The ridge P has a height H of 0.1 mm or greater and 1.0 mm or less. The ridge P has a width W2 of 0.1 mm or greater and 2.0 mm or less. A curvature radius Rc of the second corner P2 and a curvature radius Rd of the third corner P3 are equal to or less than 0.2 mm. Included angles ?1, ?2, ?3 and ?4 of the ridge P are 80° or greater and 100° or less. A tire which is obtained by the mold 32 has small grooves with a reversed shape of the ridge P.

Abstract: A pneumatic tire comprises a tread portion provided with sipes, the sipes each having a zigzag configuration at any depth from the top of the sipe to a certain depth, and the zigzag configuration having vertexes Q1 on one side of the zigzag and vertexes Q2 on the other side of the zigzag, wherein as the depth increases from the top of the sipe to said certain depth, the vertexes Q1 shift in the longitudinal direction of the sipe and the direction of the shift is turned at least once such that the vertexes Q1 first shift towards one direction then towards the other direction, thereby describing a zigzag line extending from the top of the sipe to said certain depth and having at least one tuning point, but the vertexes Q2 describe lines which are linear or less zigzag when compared with the zigzag lines described by the vertexes Q1.

Abstract: A tread portion (4) of a tire includes a first vertical groove (10), a second vertical groove (12), a subvertical groove (14), a first lateral groove (16), a second lateral groove (18) and a third lateral groove (20) on a surface thereof. The tread portion (4) further includes a first block (24), a second block (26), a third block (28) and a fourth block (30). Each of the blocks (24), (26), (28) and (30) has a siping (S). The siping (S) takes a zigzag shape. Each of the blocks (24), (26), (28) and (30) has a large number of small grooves (G). The shape of the small groove (G) constitutes a part of a wavy curve extended in an axial direction. The small groove (G) has a width which is equal to or greater than 0.1 mm and is equal to or smaller than 2.0 mm and a depth which is equal to or greater than 0.1 mm and is equal to or smaller than 1.0 mm. The small groove (G) has a pitch which is equal to or greater than 0.5 mm and is equal to or smaller than 5.0 mm.

Abstract: It is an object of the present invention to improve the running performance on snowy and icy roads, and for this purpose, blocks provided with sipes are formed at a tread portion. The sipes include an open top end that opens at a block surface and a bottom, and a configuration of the sipes in a plane parallel with the block surface comprises a zigzag part extending in the length direction of the sipes. The zigzag part displaces upon turning back to one side and to the other side in a length direction of the sipes in the course from the open top end to the bottom. At least one block includes a first sipe and a second sipe which depths of the turn-back points of displacement from the open top end and/or positions of the turn-back points of displacement in the length direction differ from each other.