a spike tire for a vehicle and which includes a pin receptacle hole formed on the tread surface of the tire ; a spike pin retractably protrudable from the pin receptacle hole ; a biasing mechanism for continuously urging the spike pin to protrude from the pin receptacle hole ; and an actuating member of a shape memory alloy capable of restoring a memorized shape when warmed to a predetermined temperature by the heat generated in the tire as a result of operation of the vehicle on a non - frozen or snow - free road surface , to thereby retract the spike pin into said tire against the action of the biasing mechanism . the spike pin is automatically protruded and retracted depending upon road conditions based on a temperature difference between a frozen or snowed road surface and a non - frozen snow - free road surface . on a non - frozen bare road , the spike pin is automatically retracted into the pin receptacle hole by restoration of a memorized shape of the shape memory alloy thereby preventing damage and abrasive wear of road surfaces and the resulting generation of pollutional dust .