A tire or tyre is a covering provided on the circumference of wheels of vehicles. The functions of tires is to dampen oscillations due to uneven surface of the road, to prevent wear and tear of the wheel, to provide a high friction bond between the vehicle and the road for proper acceleration and handling of the vehicle. They are usually made of synthetic rubber.
Snow tires are special tires designed to run on snow, ice, wet roads, sleet, slippery roads and mud. They have better traction and handling properties. Snow tires differ from regular tires in the following ways:
Hardness. They are made up of softer rubber, which heats up quicker. The softness and hardness of tire rubber depends upon the amount of carbon black in it. For summer tires, the amount of carbon black is more and for snow tires the amount of carbon black in the rubber is less. Rubber becomes brittle at lower temperatures hence summer tires are not suitable to be used in winters.
Treading. The crown or the outer perimeter of tires has jagged pattern on it known as tread. The function of tread is to provide grip during rain or snow. The summer tires have smaller tread on them. The snow and mud tires have larger tread blocks on them hence they are noisier.
Sipes. Sipes are small slits provided on the sides of tires to provide flexibility to tread blocks on the tyre. The function of sipes is to disperse water and snow. They improve traction by providing an additional biting edge to the tyre and are helpful on ice, snow, mud and sand.
Grooves. Grooves are voids on the tires designed to facilitate dispelling of water or snow. Deeper grooves provide better handling and control of the vehicle in snow.
Void Ratio. Void ratio is related to the amount of rubber coming in contact with the road. It is defined by the voids or open spaces on the tyre. A high void ratio accelerates the potentiality to drain water. For snow tires a high void ratio is required.
Aquaplaning. One of the functions of tires is to remove water from the treads on wet roads. When the tire rotates, the treads push water into grooves and sipes, from where the water is pushed out. If the water does not go out properly then the vehicle slides which may cause accidents. This sliding of the tire on water is called aquaplaning. Hence the depth and pattern of treads is very important.
Metal studs. Most snow tires have metal studs fabricated in the tread. This provides better grip on snow and ice. A place where the weather is extreme, the law makes it mandatory to use snow tires. However snow tires are extremely noisy and wear out fast on dry roads. Further, they wear out the road also.
Markings on Snow Tires. The tires designed for Mud and snow are marked with M&S. the icon of mountain and snow flake designates that the tire meets snow testing standards of American Society for Testing and Materials. It mandates that snow tires should have a traction index of more than 110.
