A system that prevent the spar tire of a vehicle from being thrusted forward into the fuel tank during a vehicle collision is disclosed. The forward motion of the spare tire from the rear collision is feasibly converted, thereby preventing the spare tire from directly impacting a fuel tank placed in front of the spare tire and improving vehicle stability. A stopper for the spare tire includes a forward motion blocking arm and a direction conversion arm. The system also includes a pivot axis located parallel to a lateral direction of the vehicle, a forward motion blocking arm protruding out from the pivot axis toward the front of the spare tire installed underneath the vehicle body and a direction conversion arm protruding out from the pivot axis between an upper portion of the spare tire and the lower portion of the vehicle body.