PURPOSE: To prevent car slip and dust pollution by fixing a stud pin on a tyre and fitting a pin main body to the outside of the stud pin in a freely slidable manner together with providing a solid expansible body between them so that the stud pin comes out of or goes inside the tyre tread surface in accordance with road conditions.

CONSTITUTION: A large number of pins 3 are embedded in the tread 2 of a tyre 1. A base plate 5 made of titanium alloy or the like, which extends outward and abuts on a ply player 4 within a tyre 1 in its shape is provided in the base part of a pin 3. And a recessed part 6 is formed in the middle of said base plate 5 facing the ply layer 4, in order to obtain reliable sucker action. In addition, a stud pin 7 made of titanium alloy or the like is erectd in the middle part of the base plate 5 on the outer surface side of the tyre, so that a pin main body 8 made of titanium alloy or the like can be fitted in a freely slid manner. Further, a solid expansible body 10 made of urethane rubber or the like is fitted on the outside of the pin main body 8. With this contrivance, when a vehicle travels on a snow-covered road, cooling effect of snow shrinks the said expansible body 10, pushes down the pin main body 8, and makes the stud pin 7 to project.