SPIKE TIRE

PURPOSE:To prevent damage of a road surface and generation of dust, by providing a working member made of shape-memory alloy between both flanges of a spike pin and its guide pin, so as to vary an amount of projection of the spike pin by heat generated in a tire. CONSTITUTION:A working member 9 made of shape-memory alloy is provided between flanges 5 and 6. When a vehicle is running on a frozen road, a tire 1 is cold and the working member 9 is in plastic condition. Therefore, it is compressedly deformed by a biasing force of a spring 10 to move the flanges 5 and 6 away from each other, and is inserted between support surfaces 5a and 6a to maintain the spike pin 3 under a projected condition. On the other hand, when the vehicle is running on an unfrozen road, the working member 9 is heated by heat generated in the tire 1. As the working member 9 is made of shape-memory alloy, it is returned to its memorized shape and gets out of between the support surfaces 5a and 6a. Accordingly, the spike pin 3 is retracted into the tire 1. In this manner, the spike pin may be automatically projected and retracted in dependence upon a frozen condition of a road surface, thereby preventing damage of the road surface and generation of dust.