Patent ID: 7487810

Claim:
A pneumatic tire comprising a tread portion having tread elements each provided with a sipe, wherein the sipe is open to a upper surface of the tread element, and has an open top end including a zigzag part and a bottom in an inner side in a radial direction of the tire, wherein the sipe comprises: a first portion in which the zigzag part of the open top end extends to a side of the bottom in a state of being inclined to one side of a longitudinal direction of the sipe; a second portion connected to an inner side in a radial direction of the first portion, and in which the zigzag part extends to the side of the bottom in a state of being inclined in an opposite direction to the first portion; and a third portion connected to an inner side in a radial direction of the second portion, and in which the zigzag part extends to the side of the bottom in a state of being inclined in an opposite direction to the second portion, the zigzag part extends from the open top to the bottom while substantially keeping its zigzag shape including an amplitude and a pitch, and the sipe satisfies the following relation (1): α1>α2>α3 (1) where α 1 is a ratio (a 1 /h 1 ) between a displacement length a 1 of the first portion along the longitudinal direction of the sipe and a length h 1 in a radial direction of the first portion, α 2 is a ratio (a 2 /h 2 ) between a displacement length a 2 of the second portion along the longitudinal direction of the sipe and a length h 2 in a radial direction of the second portion, and α 3 is a ratio (a 3 /h 3 ) between a displacement length a 3 of the third portion along the longitudinal direction of the sipe and a length h 3 in a radial direction of the third portion, and wherein the first portion inclines at an angle θ 1 with respect to a tire-radial line when viewing from the front of the sipe surface, the second portion inclines at an angle θ 2 being opposed to the angle θ 1 with respect to the tire-radial line when viewing from the front of the sipe surface, the third portion inclines at an angle θ 3 being opposed to the angle θ 2 with respect to the tire-radial line when viewing from the front of the sipe surface, and the sipe satisfies the following relation: θ1>θ2>θ3.