Contact patch is the name applied to the area of a vehicle's tire that is in contact with the road surface. The shape of a tire's contact patch can have a great effect on the handling of the vehicle to which it is fitted.
Specifically, for the type of wide tire fitted to many modern performance cars, a contact patch that is wider than it is long will increase the tendency for the vehicle to 'tramline' or follow uneven road contours.
Furthermore in front wheel drive cars, the offset between the centroid of the contact patch and the point about which the wheel steers can lead to a condition known as understeer.
