A tire is a ring of material that covers the rim of a wheel. Most road vehicles and many other vehicles use rubber tires. Tires help vehicles to move smoothly. Some metrotrains and trams also use rubber tires on their steel wheels to provide better traction than the steel tires of other trains.
Tires need to be changed after their treads wear away. Driving with worn tires is very dangerous. It can cause the tire to explode and the driver to lose control.