If you have a flat tire and install the spare, you should know whether the spare tire is speed restricted. Car manufacturers often use spare tires that are not the same type of tire as the four regular car tires.
Your car's spare tire may be one of several options. A full-size spare is the same tire model and size as the original tires on the car. A full-size lightweight or temporary spare is the same size as the car tires, but is mounted on a lightweight rim and has less tread depth than a regular tire. A compact spare is narrower that the regular tires, but has the same diameter.
Temporary and compact spare tires come with a recommendation that they be driven no faster than 50 miles per hour. The speed rating tables lists a rating designation of N for temporary spare tires. An N rating indicates a tested safe speed of 87 mph.
The safest course is to drive no faster than 50 mph on a temporary spare. If a "N" speed rating is on the side of the tire, it is rated as safe to drive at highway speeds for a short distance.
