Pneumatic tire including tread with main grooves

A pneumatic tire, comprising:

• main grooves formed on a tread of said tire, each of said main grooves extending substantially in a circumferential direction of said tire;
• transverse grooves formed on said tread, each of said transverse grooves connecting adjacent main grooves and extending obliquely with respect to a widthwise direction of said tire;
• and blocks each having a substantial parallelogram shape formed by said adjacent main grooves and adjacent transverse grooves, each of said block having an acute corner portion and an obtuse corner portion and also having a groove side extending along one of said main grooves between said acute corner portion and said obtuse corner portion,
• wherein an inclination angle of said groove side at said one of said main grooves that is outermost in said widthwise direction of said tire of each of said blocks increases from said obtuse corner portion toward said acute corner portion, said inclination angle being defined by an angle formed between an inclination direction of said groove side and a radial direction of said tire at a transverse cross-section of said tire, and
• wherein an extending direction of said one of said main grooves formed between adjacent blocks at a tread surface level is inclined toward one side of said one of said main grooves with respect to said circumferential direction of said tire, while an extending direction of said one of said main grooves formed between adjacent blocks at a groove bottom level is inclined toward the other side of said one of said main grooves with respect to said circumferential direction of said tire.