What is a tyre
A tyre is a rubber coated construction that is often inflated and surrounds a metal wheel to form a soft contact with the ground
A tyre is a complex mixture of many materials and layers that form a rubber tyre. The main features to focus on are the tread, the side wall and the carcass.
Purpose of a tyre
There are two main purposes of a tyre within the automobile industry. The first is to provide the wheel with grip. This comes mainly in the form of the type of compound of rubber that the tyre tread is made from. This grip allows the power from the engine to be passed through the tyre and propel the car on the surface below. It also allows grip for cornering and braking to be transmitted through to the surface and keep the vehicle on course as directed by the driver.
The other purpose is to provide a soft contact with the road, which is why they are filled with air so that there is a cushion between the metal wheel and the road surface which lends a helping hand to the suspension as well.
Tyre numbers explained
The numbers on the side of a tyre, for example, 195/55/R15, are a universal format used within the tyre industry to describe 3 aspects of the tyre. The first number (195) relates to the width of the tyre in millimetres. The second number (55) is a percentage of the first number to say how deep the sidewall is. So in this case, the depth of the sidewall is 55% of 195mm, which would be 107.25mm. The final number, often started with a R is the diameter of the metal wheel in inches. Therefore this tyre has a 15 inch wheel fitted to it.
Types of tyre
There are numerous forms of tyre in the automotive industry. They range from all-terrain to slick circuit tyres. Within tarmac motorsport the type of compound the tyres are constructed from is also important. A common selection is a hard tyre, soft tyre and a wet tyre. A soft tyre would provide a lot of grip for the car and allow it to corner, accelerate and brake faster out on circuit. However, the soft tyre would not last very long as the compound would disintegrate faster.
A hard compound tyre would last considerably longer than the soft tyre, but would provide less grip for the car. This would be used for endurance stints of a race in dry weather conditions. A wet tyre would be used in the rain and wet track conditions. This has cuts in the tread to move water away from the surface to allow the tyre to grip with the road surface. It is also often quite a soft compound to gain as much grip as possible in the wet slippery conditions.