Pneumatic tire with tread having chamfered circumferential groove portion of bent auxiliary groove

A pneumatic tire comprising a tread provided with at least two circumferential main grooves and a rib defined in a tread central portion by two of the circumferential main grooves, wherein

• an auxiliary groove is formed in the tread central portion, the auxiliary groove having a circumferential groove portion extending in a tire equator direction and an axial groove portion extending from an end of the circumferential groove portion in such a manner that the axial groove portion is bent at an acute angle to the circumferential groove portion, and
• at least an end of the auxiliary groove is open into one of the two circumferential main grooves,
• wherein the rib is located on the tire equator,
• wherein the circumferential groove portion of the auxiliary groove has a chamfered portion inclined with respect to a surface of the tread on at least one groove wall of both groove walls sectioning the circumferential groove portion,
• wherein the chamfered portion is formed on one groove wall of the circumferential groove portion only in a side of the axial groove portion,
• wherein the width of the chamfered portion gradually decreases from the axial groove portion side end of the circumferential groove portion to a terminated end of the circumferential groove portion,
• wherein the acute angle is formed between the circumferential groove portion and the axial groove portion,
• wherein the chamfered portion is provided only in a half tread portion on one side of the tire equator, and
• wherein the other half tread portion on the other side of the tire equator is not provided with an auxiliary groove having a chamfered circumferential groove portion extending in a tire equator direction and an axial groove portion extending from an end of the chamfered circumferential groove portion in such a manner that the axial groove portion is bent at an acute angle to the chamfered circumferential groove portion.