What is a pneumatic tire? What are the major components of pneumatic tire?

A tire is a round shape rubber that is used to cover the metallic or alloy rim of the wheel. Its purpose is to protect the rim and to improve the performance of the wheel by providing traction between the vehicle and road. It also acts as a cushion to absorb the bumpy parts of the roads.

In the past the tires were simply bands of metal that were fixed around the wooden wheels to prevent the wear the tear of the wheels. After the development of rubber the tires were made up by them but they were solid tires that cannot be filled with air directly. Rubber tubes were inserted to keep them round. Today the modern tires also known as pneumatic tires are made up from synthetic rubber, natural rubber, fabric, wire and other chemical compounds. There are two main portions of these modern pneumatic tires first is the tread that is used to provide traction to the vehicle while other is the body that is a containment for compressed air. The main components of the pneumatic tire is explained below:

Tread

The tread is the part of the tire that comes in contact with the road surface. The tread is a thick rubber, or rubber/composite compound formulated to provide an appropriate level of traction that does not wear away too quickly. Treads are often designed to meet specific product marketing positions. High performance tires have small void ratios to provide more rubber in contact with the road for higher traction, but may be compounded with softer rubber that provides better traction, but wears quickly.

Tread lug

Tread lugs provide the contact surface necessary to provide traction. As the tread lug enters the road contact area, or footprint, it is compressed. As it rotates through the footprint it is deformed circumferentially. As it exits the footprint, it recovers to its original shape.

Tread void

Tread voids provide space for the lug to flex and deform as it enters and exits the footprint. Voids also provide channels for rainwater, mud, and snow to be channeled away from the footprint. The void ratio is the void area of the tire divided by the entire tread area. Low void areas have high contact area and therefore higher traction on clean, dry pavement.

Rain groove

The rain groove is a design element of the tread pattern specifically arranged to channel water away from the footprint.

Sipe

Tread lugs often feature small narrow voids, or sipes, that improve the flexibility of the lug to deform as it traverses the footprint area. This reduces shear stress in the lug and reduces heat build up.

Wear bar

Wear bars (or wear indicators) are raised features located at the bottom of the tread grooves that indicate the tire has reached its wear limit.

Bead

The bead is that part of the tire that contacts the rim on the wheel. The bead is typically reinforced with steel wire and compounded of high strength, low flexibility rubber. The bead seats tightly against the two rims on the wheel to ensure that a tubeless tire holds air without leakage. The bead fit is tight to ensure the tire does not shift circumferentially as the wheel rotates. The width of the rim in relationship to the tire is a factor in the handling characteristics of an automobile, because the rim supports the tire's profile.

Sidewall

Uneven sidewall wear, down to fabric plies, due to significant under-inflation. The sidewall is that part of the tire that bridges between the tread and bead. The sidewall is largely rubber but reinforced with fabric or steel cords that provide for tensile strength and flexibility. The sidewall contains air pressure and transmits the torque applied by the drive axle to the tread to create traction but supports little of the weight of the vehicle, as is clear from the total collapse of the tire when punctured. 

Shoulder

The shoulder is that part of the tire at the edge of the tread as it makes transition to the sidewall.

Ply

Plies are layers of relatively inextensible cords embedded in the rubber to hold its shape by preventing the rubber from stretching in response to the internal pressure. The orientations of the plies play a large role in the performance of the tire and is one of the main ways that tires are categorized.