A SPARE tire is a type of tire that is kept in the trunk of a car as a backup in case of an emergency. RADIAL tires are constructed with the cords running perpendicular to the direction of travel, providing better handling and improved fuel efficiency. RETREAD tires are tires that have been used before and have had new treads applied to them, making them a more economical option. All three of these types of tires are kinds of tires.