A stud pin includes a tip, a body portion that supports the tip, and a lower flange connected to the body portion at an end on an opposite side to the end surface. A profile shape of the lower flange and a body profile shape of the body portion are anisotropic shape. The flange profile shape includes four or more first flange protrusion portions projecting toward the longitudinal direction and two second flange protrusion portions projecting toward the lateral direction. The body profile shape includes four or more first body protrusion portions projecting toward the lateral direction and two second body protrusion portions projecting toward the longitudinal direction.

A stud pin includes a tip including a tip end surface configured to come into contact with a road surface and a trunk portion that supports the tip and extends in one direction. The trunk portion includes an upper flange disposed at a first end of the trunk portion, the tip being fixed to the upper flange, and a lower flange disposed at a position to a side opposite the upper flange of the trunk portion. An upper end surface of the upper flange from which the tip protrudes includes a recessed surface, the recessed surface including a smooth inclined surface recessing in a curved manner or a linear manner toward the lower flange with advancement toward a protruding base portion of the tip.

First direction ridge patterns and second direction ridge patterns are lined-up alternately at a decorative concave portion 18. Plural main ridges 22A through 22D and sub-ridges 26A through 26D, which project-out from a bottom surface 18A, are formed at a first direction ridge pattern 20. The respective ridges are disposed in parallel such that ridge extending directions are a same direction. Light reflection patterns are different at a main ridge region 24, 34 and a sub-ridge region 28, 38.

A studded tire includes stud pins embedded in a road contact surface of a tread portion 1; the rubber composition forming the tread portion containing at least one of natural rubber, styrene-butadiene rubber, and butadiene rubber, from 5 to 50 parts by weight of carbon black and from 5 to 70 parts by weight of silica per 100 parts by weight of the diene rubber; a nitrogen adsorption specific surface area of the carbon black being from 50 to 120 m.sup.2/g; a CTAB specific surface area of the silica being from 80 to 190 m.sup.2/g; a rubber hardness of the rubber composition being not greater than 60; and a product of a stress at the time of 400% elongation and a bottom surface area of a flange portion on a bottom side of the stud pins being not less than 400 MPa.Math.mm.sup.2 and not greater than 850 MPa.Math.mm.sup.2.

A stud pin includes a tip including an end surface that comes into contact with a road surface, a body portion that supports the tip; and a lower flange connected to the body portion at an end on an opposite side to the end surface. A profile shape of the lower flange is an anisotropic shape in which, of imaginary rectangles circumscribing the profile shape, a first smallest rectangle with the shortest side of its four sides being the shortest and/or a second smallest rectangle with the longest side of its four sides being the shortest includes short sides and long sides of different lengths. The profile shape includes four or more first protrusion portions that project in the longitudinal direction parallel with the long sides and two second protrusion portions that project in the lateral direction parallel with the short sides.

A method for installing a stud in a tyre. The method includes identifying a stud hole for the stud in the tyre; imaging the vicinity of at least the stud hole, whereby information is received about the pattern in the vicinity of the stud hole, and using the received information to determine [i] the stud type suitable for the stud suitable in the stud hole and/or [ii] the suitable stud orientation of the stud suitable in the stud hole. The method includes providing a stud and installing it in a stud hole. The stud type of the stud is the same as the suitable stud type of a stud suitable in the stud hole; and/or the stud is installed in the stud hole in such a way that the main direction of the stud is parallel with the suitable stud orientation. Further a tyre studded by the method.

A stud pin includes a tip, a body portion, and a lower flange. A flange profile shape of the lower flange is an anisotropic shape includes short sides and long sides of different lengths, and includes four or more first flange protrusion portions that project in the longitudinal direction parallel with the long sides and two second flange protrusion portions that project in the lateral direction parallel with the short sides. A body profile shape of the body portion is a shape including body linear portions extending in a linear manner. The body linear portions are disposed facing 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 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 pneumatic tire includes stud pins inserted into holes disposed in the tire surface. The stud pins each include a body portion and a flange disposed closer to the bottom side of each of the holes than the body portion and having an outer diameter larger than the body portion. The holes each include a securing portion coming into contact with the outer peripheral surface of the body portion of the stud pin to secure the stud pin and an enlarged diameter portion disposed closer to the bottom wall side of the hole than the securing portion, having an inner diameter larger than the securing portion, and coming into contact with the outer peripheral surface of the flange of the stud pin to secure the stud pin. The side wall of the enlarged diameter portion is provided with a protrusion protruding toward the interior of the hole.

A stud pin configured to be installed in a stud pin installation hole in a tread portion of a pneumatic tire includes a tip end which makes contact with a road surface; and a buried base embedded in the tread portion; pressure from the side surface of the stud pin installation hole on the bottom portion and the trunk portion securing the stud pin. The buried base extends in one direction and includes a flanged trunk portion provided between the bottom portion and the tip portion. The bottom portion includes a plurality of first recesses formed on and along an outer peripheral surface thereof that is in contact with a side surface of the stud pin installation hole. The trunk portion includes a plurality of second recesses formed on and along an outer peripheral surface thereof that is in contact with the side surface of the stud pin installation hole.