A vehicle is consists of thousands of parts, and each component has its own unique and single function. tyre is also one of the components of the vehicle; however, with different functions from other components, it has the following four functions during the driving:

●Load-bearing no matter carrying its dead weight or people or cargo, the weight will definitely reaches its for tyres through its body, then all the weight will be borne by the four tyres, from which we can know the importance of tyres, in terms of carrying goods.

●Generating a driving force and braking force because tyres are the only parts contacting the ground surface, any action of the vehicle like: starting, driving, braking or stopping have to need the help of the four tyres to "communicate" with the ground, and achieve the inclination of divers through the tyre.

●Cushioning and shock absorption Most of the unpaved roads are full of many crushed stone, bumps, even on the paved roads, there are still lots of obstacles affecting the normal running of the car. Under such occasion, the tyre will play its superior cushioning and shock absorption, and let the vehicle move forward in a more comfortable situation. Because， the tyre is made of 50% elastic rubber, plus shock-absorbing function of the air within the tyre, making the vehicle drive comfortably at any road with poor quality.

●Changing the driving direction no matter steering or turning around, the function must be done through the four tyres of the vehicle, according to the driver's will as shown in fig.2—7.