A Tire is a cushion provided with an automotive wheel. It is mounted over the wheel rim. Before Proceeding forward please go through the previous post that gives you a clarity on the structure and types of wheels.
The functions of a tire are To-
- Support the vehicle load.
- Provide a cushion against the shocks.
- Transmit driving and braking forces to the road.
- Provide the cornering power for smooth steering.
The desirable properties of a tire are-
- The tire tread should be designed in such a manner that it permits the least amount of skidding.
- The wear on the tire must be uniform.
- The tires material should be able to take the alternate stresses while in running condition.
- The tire should be able to absorb the small undulations of the road surface.
- The tires should be designed to absorb the least amount of power due to hysteresis.
- Tire noise should be minimum.
- The tire is a rotating part must remain statically as well as dynamically balanced.
The pneumatic tires-
- Conventional tubed tire- It consists of two parts, the carcass, and the tread. The carcass is the basic structure taking various loads consisting of a number of plies wound in radial or cross-ply. The term ply rating is used to indicate the exact number of plies in the tire. The side wall is the protective rubber coating on the outside of the tire carcass designed to resist the cutting, scuffing and cracking. To prevent the tire from being thrown out the plies are attached to the rings of bundles of bronze-coated high-tension steel wire insulated with rubber. These rings fit against the rim anchoring the tire to the rim. These rings are known as beads. The tread is the part of the tire which contacts the road surface and transmits the force between the road and tire. It is made of synthetic rubber and it decides the grip, noise and wear. The void ratio is the amount of open space in the tread. There are three types of tread patterns, symmetrical, asymmetrical and unidirectional. Inside the tire is the tube which contains the air under pressure. Tube being thin and flexible takes the shape of the tire cover when inflated.
- Tubeless tire- It doesn’t need a separate tube instead the air under pressure is filled in the tire itself for which a non-return valve is attached to the rim. The inner construction of rim is almost same as the tubed tire, except that it is lined on inside with a special air retaining liner made of halogenated butyl rubber for better air impermeability with high heat and weather resistance. The bead heal in the tubeless tire sits more tightly within the flange of the rim.
Advantages of the tubeless tire over conventional tires-
- Tubeless tires have less unsprung weight.
- In case of tubed tires the heat in the compressed air has to pass through the tube material which is not a good conductor of heat, but in case of the tubeless tire, the heat is directly passed to the atmosphere.
- In tubeless tire sidewall is supple and there is no internal tube to generate friction. This helps to reduce rolling resistance.
- Tubeless tires absorb the vibrations and shock better at tire level making the ride softer and comfortable.
- Since the inner liner of the tubeless tire is not stretched like a tube, it retains the air resulting in slower leakage of air.
- The tubeless tire has a simpler assembly.
- The tubeless tire can retain air for a long time even when punctured by a nail thus reducing the chances of an accident and improving the safety.
On basis of use, the tires are classified as-
- All-season tires- They are designed by compromising on the performance, grip, noise, and life. They are made of hard rubber for longer life, which decreases the grip and cornering power. Tread is designed as a compromise between the quiet running and wet running safety.
- Summer tires- They prefer grip and performance over life and hence they are made from softer rubber. Tread is designed for maximum grip.
- Wet-weather tires- They have more Sipes, these are small slit-like grooves in tread blocks to disperse more water.
- Snow tyres-They have larger tread block pattern that makes them noisy. For extreme cases, they have small metal inserts which bite into the snow. They have a short lifespan.
- All-terrain tires- They are large and have stiffer sidewalls and bigger tread block patterns. This increases their grip on loose sand and dirt. They are noisy on normal roads.
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