Pneumatic tire

A pneumatic tire comprising:

• a tread portion provided in its tread surface with a plurality of main grooves extending continuously in the tire circumferential direction to define a plurality of land portions including at least a land portion between the main grooves and a land portion between each tread edge and an adjacent main groove,
• wherein
• at least one of said land portions is provided with sipes extending from the adjacent main groove,
• at least one of said main grooves has, in a cross-section perpendicular to the longitudinal direction of the groove, a first groove bottom and a pair of first groove walls smoothly extending from the first groove bottom to the tread surface, wherein the groove width W1 between the first groove walls is 2.0 to 20.0 mm in the tread surface, and the groove depth D from the tread surface to the first groove bottom is 10.0 mm or more,
• wherein
• in each said first groove wall, a ratio (W1/α) of the angle α (degrees) of the first groove wall with respect to the normal direction to the tread surface and the groove width W1 (mm) between the first groove walls is in a range of 1.0 to 2.0 (mm/degree),
• wherein
• the main grooves include a pair of crown main grooves disposed where one is on each side of the tire equator,
• the land portion between the crown main grooves is formed as a crown rib continuous in the tire circumferential direction,
• the crown rib has two edges respectively abutting the crown main grooves and each edge comprising external corner portions and internal corner portions,
• the external corner portions extending along the tire circumferential direction on the most outside in the tire axial direction, and
• the internal corner portions extending along the tire circumferential direction on the most inside in the tire axial direction,
• wherein
• in the external corner portions and the internal corner portions, said two edges extend in parallel with the tire circumferential direction,
• wherein
• the crown rib is provided with
• first crown sipes respectively connecting between the external corner portions of one edge of the crown rib and the external corner portions of the other edge, and
• second crown sipes respectively connecting between the internal corner portions of one edge of the crown rib and the internal corner portions of the other edge,
• wherein the first crown sipes and the second crown sipes are straight sipes inclined with respect to the tire axial direction to the same direction,
• wherein
• a crown land portion which is said land portion between the crown main grooves is provided with only the first crown sipes and the second crown sipes,
• a shoulder land portion which is said land portion between each tread edge and the adjacent main groove is provided with said sipes as shoulder sipes and lateral grooves as shoulder lateral grooves, and
• said plurality of land portions further include a middle land portion formed between the crown land portion and said shoulder land portion and provided with said sipes as middle sipes and lateral grooves as middle lateral grooves.