What is Tire?
[[File:Black Wheels in BW.jpg|alt=|thumb|A tire for a car]] [[File:Patee Rijwielen met ondoordringbare Chase Banden.jpg|thumb|upright|Old advertisement for [[bicycle]] tire]] A '''tire''' is a ring of material that covers the rim of a [[wheel]]. Most road [[vehicle]]s and many other vehicles use [[rubber]] tires. Tires help vehicles to move smoothly. Some [[rapid transit|metro]] [[train]]s and [[tram]]s also use rubber tires on their [[steel]] wheels to provide better [[traction]] than the [[steel]] tires of other [[train]]s. Tires need to be changed after their [[tread]]s wear away. Driving with worn tires is very dangerous. It can cause the tire to explode and the driver to lose control. Tires were made of leather for thousands of years, and of iron or steel for hundreds. Pneumatic tires were invented in the 1840s and again in the 1880s. They became commonplace early in the 20th century. ==Construction== Tires are made of different types of rubber. Softer rubber is used in summer or when the tires need better [[Traction (engineering)|traction]], for example, in [[auto racing]]. Tires made of harder rubber are made for long lasting performance, like long-distance truck carriers. There are many different types of tires. They come in different [[size]]s and have different tread [[pattern]]s. There are many different sizes of tires. On car and truck tires, they are marked with 3 numbers and might look like: 225/60R16. The first number is the width in [[millimetre|millimeters]] of the tire at the widest point when it is mounted and inflated. The second number is the sidewall (side of the tire) height as a [[ratio]] or [[percent]]age of the width. The last number is the wheel [[diameter]] in [[inch]]es. ;Example: Tire size: 225/60R16 :Tire width = 225mm :Sidewall height = 135mm (225 * .60 = 135) :Wheel diameter = 16 inches Very large tires (for example, tires on big [[mining]] trucks) use different [[Units of measurement|units]]. For example: 59/80R63. The first number is the width in inches of the tire. The