Contact patch – What is it and why is it important?

Whenever you ride a vehicle there are three major things that happen during your journey; acceleration, braking and change of direction. To perform all of these functions the vehicle has to exert some forces. When your car accelerates or speeds up it requires a certain push in the forward direction. And, when your car brakes it requires a large force in the opposite direction to stop. These are the longitudinal forces that help the vehicle to accelerate and decelerate. The lateral forces on the other hand help the vehicle to turn or change direction. All these forces are transferred between the tyre and the road through the small portion of the tyre that comes in contact with the road. This is the contact patch. It is the area of the tyre that sits on the road and meets the asphalt as you drive. It is the contact patch that affects the vehicles ability to deliver the required performance.

Importance of tyre contact patch

The contact patch of most of the tyres is of the size of your palm. However, different types of tyres have various contact patches depending on the tyre application. The width and length of the contact patch also vary depending on the tyre design, tyre pressure and the vehicle’s weight. For example, low profile tyres have a wider contact patch as compared to a high profile tyre. Low profile tyres that are generally used on sports cars are meant to offer high speed with increased traction and cornering performance. The short and wide contact patch allows the tyre to be in good contact with the road, offering enhanced traction, especially on dry roads. The wide contact patch is one of the significant characteristics of low profile tyres used in racing cars. A high profile tyre on the other hand has a narrower but long contact patch. Regular passenger cars and trucks have high profile tyres that are effective in offering a smooth ride.

Also, when you look at a premium-priced performance tyre the contact patch is usually slightly bigger as compared to a normal economic tyre. The key benefit of having tyres with a larger contact patch is in hard braking or an emergency situation the tyres will stop faster. So, when you are buying new on-road tyres, the price can be a part of the equation but so is your safety.

How does the air pressure in the tyre affect the contact patch?

The contact patch of your tyre is a function of the air pressure present in it. As seen in the figure below an overinflated or underinflated tyre bulges at the part that is in contact with the road. An overinflated tyre is in contact with the road at the centre of the tread whereas an underinflated tyre is in contact with the road at the tread edges. In both cases, several inches of the contact patch is lost. This greatly affects the handling and performance of the vehicle. And, not to mention the excessive tyre wear caused due to improper air pressure. Hence, to have even contact with the road it is necessary to maintain the correct air pressure in the tyres.

As your vehicle applies power to move forward, brake or turn, remember it’s the contact patch of the tyre that deals with all of these dynamics that happen all at once or within seconds.