Stud pin and pneumatic tire

A stud pin mountable in a stud pin installation hole of a tread portion of a pneumatic tire, the stud pin comprising:

• a buried base portion configured to be embedded in the stud pin installation hole that extends in a tire radial direction;
• and
• a tip portion configured to project from a road contact surface of the tread portion when the buried base portion is embedded in the stud pin installation hole,
• the tip portion comprising an end surface with a concave octagonal profile shape comprising one first recessed portion and seven protrusion portions that include one first protrusion portion on a side opposite the first recessed portion;
• a pair of first protrusion portion sides that form the first protrusion portion;
• a pair of lateral protrusion portions or a pair of lateral sides that are provided on outermost positions of the concave octagonal profile shape in a lateral direction perpendicular to a rear direction directing from a corner of the first protrusion portion toward a corner of the first recessed portion;
• and
• a pair of inclined sides that extend in the rear direction and inward in the lateral direction from corners of the pair of lateral protrusion portions or ends of the pair of lateral sides, the pair of inclined sides being parallel to one of the pair of first protrusion portion sides respectively.

A pneumatic tire with a designated rotation direction, comprising:

• a stud pin mounted in a stud pin installation hole of a tread portion;
• the stud pin comprising:
• a buried base portion embedded in the stud pin installation hole that extends in a tire radial direction;
• and
• a tip portion that projects from a road contact surface of the tread portion when the buried base portion is embedded in the stud pin installation hole,
• the tip portion comprising an end surface with a concave octagonal profile shape, the concave octagonal profile shape comprising:
• one first recessed portion;
• one first protrusion portion on a side opposite the first recessed portion;
• a pair of first protrusion portion sides that form the first protrusion portion;
• a pair of lateral protrusion portions or a pair of lateral sides that are provided on outer most positions of the concave octagonal profile shape in a lateral direction perpendicular to a rear direction directing from a corner of the first protrusion portion toward a corner of the first recessed portion;
• and
• a pair of inclined sides that extend in the rear direction and inward in the lateral direction from corners of the pair of lateral protrusion portions or ends of the pair of lateral sides, the pair of inclined sides being in parallel to one of the pair of first protrusion portion sides respectively;
• and
• the stud pin being disposed with the first protrusion portion facing a leading side in a tire circumferential direction and the first recessed portion facing a trailing side.