The image above is probably the first thing that pops into your mind when you hear the word "tyre."
You're not completely wrong, however, the image above is technically not just of a tyre. It's actually composed of two things - a wheel and a tyre. It is important to understand that these two components together form the complete structure seen in the picture that allows the vehicle to take you from one place to another.
This is a tyre:
And this is a wheel :
A tyre thus refers to the round, black coloured, inflated rubber component that is mounted on a wheel. It is the tyre that is responsible for features like grip, traction and shock absorption. The wheel has pretty much no role to play in such things since there is absolutely no contact between the wheel and the ground.
It's important to note that although rubber makes up a major component of tyres, there are also several other important components and materials like steel, fabrics and synthetic materials that are involved in the manufacturing of tyres today. All these components are then moulded together and form the modern-day tyre that we see on our vehicles. All the components fit together like a jigsaw puzzle and support each other structurally as well as functionally.
So now that you know the basics when it comes to tyres, its time to delve into more details about the different components that make up a tyre.
However, before we start, we suggest you first watch the video below as it'll help you better understand and visualize the different components of a tyre.
A TYRE AND ITS COMPONENTS
A tyre has three components:
- The belt system - structural support system made of steel. Present between the tread system and the casing.
- The tread - outermost layer of rubber on a tyre, a part of which (tread cap) also makes contact with the road.
- The tyre casing - also known as the body of the tyre, the tyre casing sits below the steel belts and includes components like the bead, sidewall, body ply and the inner liner/tube.
The Belt System
The belt system in a tyre is mostly composed of steel and is present in between the casing and the tread as a structural support that provides strength and stability to the tread area. The tread undergoes a lot of stress and a belt system is necessary for the tread to be robust during such circumstances. The belt system is usually composed of two plies of steel cords that are placed at opposite angles to each other. A common belt configuration is two stacked plies of steel cords.
The Tread
The tread refers to the outermost rubber layer of a tyre that is in contact with the road. It usually has two layers that contain different compounds - a tread base and a tread cap. The tread base sits on top of the belt system and moulds to the belt system during curing. This helps in stabilizing the belt plies and provides an additional stability that keeps the plies stable and rigid.
The tread cap is the outermost layer of the tyre as well as the tread system. It is usually composed of a higher quality and grippier rubber compound which is also abrasion-resistant. The tread cap which has the tread pattern carved onto it works along with the tread base and the tread design/pattern to provide the necessary characteristics of the tyre unique to it.
Also See: Tyre Maintenance 101: Your Bible For Longer Tyre Life
The casing/ body
The casing /body of the tyre is made up of the following components:
- Body ply
- Bead
- Innerliner/Tube
- Sidewall
Body Ply: The body ply consists of multiple levels of "plies" that are composed of several different fabrics like nylon, polyester or rayon cords. These plies are sandwiched between layers of rubber that help them bond with the other components of the tyre. The main purpose of the body ply is to provide structural strength to the tyre. Different blends of polyester, nylon and rayon are used according to how the casing needs to be designed for each tyre. Each of them have different advantages like polyester, for example, is low in weight but has excellent strength and rubber adhesion. It also has heat dissipation characteristics.
Bead: Tyre bead are bundles that secure the tyre to the wheel in an airtight manner. Beads are made up of steel and are wound together to form a cable type configuration. The bead bundles are held in place with the help of casing plies. A rubber compound known as a bead filler is blended with the bead configuration. The compound is different on the outside and on the inside owing to the difference in the outside and inside environments for the tyre.
Innerliner/Tube: Tubeless tyres sport an inner liner whereas tubed tyres sport a tube and a flap in place of the inner liner. Let's understand what both of these mean:
The inner liner is a rubber compound used to retain the inflation pressure inside the tyre. A specific rubber compound is used as an air seal inside the tyre. This inner liner layer has no cord reinforcement and is similar to an inner tube. Tubeless tyres do not need an inner tube as they are fitted onto an airtight rim.
A tube, or more specifically an inner tube, is a thin rubber bladder that is inserted into a tubed tyre to ensure that the tyre is airtight and leak free. Since tubed tyres do not sit on an airtight rim, they need to be fitted with an inner tube to ensure that there are no leaks.
Sidewall: The tyre sidewall refers to the rubber compound used to cover the body plies on the sides of the tyre. The main function of the tyre sidewall is to prevent the air from escaping and protect the body plies on the sides of the tyre from road and curb damage. Some sidewalls may also contain extra components that serve to increase lateral stability.
TYRE COMPOSITION
Image Credits: ustires.org, oceanicdirect.com.au, carbiketech.com
