Tyre contact patch

  • Feb 9, 2012
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The contact patch of a tyre is the section of the tyre's tread that is in physical contact with the road surface. It differs for different types of tyres and sometimes under different road conditions. Read on to know more

Tyre contact patch

The contact patch of a tyre is the rubber on the tyre tread that touches the road surface. The contact patch of the tyre is the only physical connection between a vehicle and the road surface. The size of a tyre, its tread pattern and the pressure pattern on the contact patch of a tyre determines to a significant extent how a vehicle rides, handles and brakes under different situations. 

Different types of tyres have different contact patches depending on the purpose of a tyre. For example, snow tyres are narrow in width with deep groves to dig into the snow for adequate traction without allowing the vehicle to sink into the snow, as opposed to slick tyres used in racing cars on dry roads. Slick tyres have a wide contact patch with no grooves or sipes. This alloys the entire tyre to be in contact with the road for enhanced traction that allows a vehicle to carry more speed especially around corners.

Pneumatic tyres, short for rubber tyres inflated with air, are flexible in nature and hence the contact patch of such tyres differ under different load conditions and tyre pressures. The contact patch of a tyre also varies when a vehicle is stationary and when it is moving. Statistically, a heavier load on the tyre results in a larger contact patch, while more inflation results in a narrower contact patch. 

Contact patch

As you may have noticed, tyres of an overloaded vehicle or those with less air cause the tyre to bulge at the bottom over the part that is in contact with the ground. This indicates greater pressure being exerted from the contact patch to the sidewall at that point instead of a more even spread over the entire sidewall of the tyre. This has negative effects on the ride and handling and fuel economy of a vehicle, not to mention the added wear on the tyre. 

An over inflated tyre will have to take added pressure on the specific pressure points of the contact patch of the tyre with less pressure going to other areas of the contact patch. This will result in certain loss of traction from the contact patch of the tyre leading to less control over the vehicle, not to mention added strain on the rubber of the tyre causing it to expand. An over inflated tyre will allow more vibrations to pass from the road surface to the suspension of a car resulting in a bumpier ride and the suspension will have to work harder to cope with the vibrations. 

It is, therefore, crucial to maintain the correct tyre pressure recommended by the car manufacturer for a safe, comfortable and enjoyable drive. 

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