A stud pin includes a tip including an end surface configured to come into contact with a road surface, a body portion configured to support the tip, and a lower flange. The flange profile shape of the lower flange is an anisotropic shape. The flange profile shape includes four or more first flange protrusion portions that project in the longitudinal direction and two second flange protrusion portions that project in the lateral direction. A tip profile shape of the tip is a shape including tip linear portions extending in a linear manner. At least one of the tip linear portions extends along a portion of the flange profile shape between two adjacent protrusion portions of the first flange protrusion portion and the second flange protrusion portion along the outer circumference of the flange profile shape.

A stud is inserted into a tread portion of a tire. The first stud includes a tip end protruding from the tread portion for contacting a surface, the tip end comprising a radially outer portion with a first surface, a second surface, a third surface, a fourth surface, a fifth surface, a sixth surface, and a seventh surface, the first surface defining an irregular quadrilateral and extending radially inward from the fourth surface toward a planar side of the tip end; and a base including a flanged bottom portion provided on an end opposite the tip end and extending radially outward, a stump portion provided between the bottom portion and the tip end, and a shank portion interconnecting the stump portion and the bottom portion, the base being embedded and secured in the tread portion of the tire in which the first stud is installed, the bottom portion having a tear-drop shape comprising three planar sides and one semi-cylindrical side.

A ground contact region of the tread portion of a studdable tire includes a center region located over a range corresponding to a length of 5 to 25% of a ground contact width from a tire centerline on each of both sides of the tire centerline in a tire width direction; and two shoulder regions located on both sides of the center region in the tire width direction. In each of the center region and the shoulder regions, a plurality of the stud pin installation holes are disposed along each of four or more pin arrangement lines extending in a tire circumferential direction. An average value of adjacent intervals between the pin arrangement lines in the center region is larger than an average value of adjacent intervals between the pin arrangement lines in each of the shoulder regions.

In a stud pin, a flange contour shape of a lower flange is an anisotropic shape in which, among imaginary rectangles circumscribing the contour shape, the smallest rectangle includes short sides and long sides having different lengths. The flange contour shape includes first recess portions on each of portions of the flange contour shape extending along the short sides, the first recess portions being curved toward a centroid of the flange contour shape, and the flange contour shape includes a second recess portion on portions of the flange contour shape extending along the long sides, the second recess portions being curved toward the centroid of the flange contour shape. A body contour shape of a body portion is a polygonal shape including vertex angles in a same number as the first and second recess portions, and the vertex angles are disposed facing the first and second recess portions.

A tire mold comprises sector molds for forming a tread portion of a tire and mold pins provided on the sector molds for forming insertion holes in the tread portion. The insertion holes each comprise a first hole portion with a first inner diameter where a body portion of a stud pin is disposed and a second hole portion with a second inner diameter greater than the first inner diameter where a bottom flange portion of the stud pin is disposed. The mold pins each comprise a trunk portion with a first outer diameter for forming the first hole portion and a tip portion with a second outer diameter greater than the first outer diameter for forming the second hole portion.

A tire mold comprises sector molds for forming a tread portion of a tire and mold pins provided on the sector molds for forming insertion holes in the tread portion. The insertion holes each comprise a first hole portion with a first inner diameter where a body portion of a stud pin is disposed and a second hole portion with a second inner diameter greater than the first inner diameter where a bottom flange portion of the stud pin is disposed. The mold pins each comprise a trunk portion with a first outer diameter for forming the first hole portion and a tip portion with a second outer diameter greater than the first outer diameter for forming the second hole portion.

A heavy-duty tire includes a tread part formed such that the tread part includes a crown profile including tire equator, and a pair of shoulder profiles extending from outer sides of the crown profile to tread edges. In a tire cross section including tire rotation axis in 5% internal pressure state in which the tire is mounted to a normal rim, filled with air at internal pressure of 5% of normal internal pressure and loaded with no load, each of the crown and shoulder profiles has an arc shape convex toward tire radial direction outer side such that ratio Rc/Rs of curvature radius Re of the crown profile to curvature radius Rs of each shoulder profile is 7.0 or more, and a tire axial direction distance from the equator to a connecting point between the crown profile and each shoulder profile is 0.70 or more times a tread half width.

A stud is inserted into a tread portion of a tire. The first stud includes a tip end protruding from the tread portion for contacting a surface, the tip end comprising a radially outer portion with a first surface, a second surface, a third surface, a fourth surface, a fifth surface, a sixth surface, and a seventh surface, the first surface defining an irregular quadrilateral and extending radially inward from the fourth surface toward a planar side of the tip end; and a base including a flanged bottom portion provided on an end opposite the tip end and extending radially outward, a stump portion provided between the bottom portion and the tip end, and a shank portion interconnecting the stump portion and the bottom portion, the base being embedded and secured in the tread portion of the tire in which the first stud is installed, the bottom portion having a tear-drop shape comprising three planar sides and one semi-cylindrical side.

In a stud pin, a flange contour shape of a lower flange is an anisotropic shape in which, among imaginary rectangles circumscribing the contour shape, the smallest rectangle includes short sides and long sides having different lengths. The flange contour shape includes first recess portions on each of portions of the flange contour shape extending along the short sides, the first recess portions being curved toward a centroid of the flange contour shape, and the flange contour shape includes a second recess portion on portions of the flange contour shape extending along the long sides, the second recess portions being curved toward the centroid of the flange contour shape. A body contour shape of a body portion is a polygonal shape including vertex angles in a same number as the first and second recess portions, and the vertex angles are disposed facing the first and second recess portions.

A stud is configured to be inserted into a tread portion of a tire. The stud includes a tip end protruding from the tread portion for contacting a surface, and a base including a flanged bottom portion provided on an end opposite the tip end and extending radially outward, a stump portion provided between the bottom portion and the tip end, and a shank portion interconnecting the stump portion and the bottom portion. The base is embedded and secured in the tread portion of the tire in which the stud is installed. The bottom portion has a tear-drop shape consisting of three planar sides and one semi-cylindrical side. The stump portion has a polygonal shape consisting of three concave sides, two convex sides, and one planar side.