What is the term for the part of the tire that touches the road?

The term for the part of the tire that touches the road is known as the contact patch. This area is crucial because it is where the tire makes direct contact with the roadway, providing the necessary friction and grip needed for safe acceleration, braking, and cornering. The size and quality of the contact patch can significantly affect the vehicle's handling characteristics, stability, and overall performance.

In contrast, the sidewall refers to the outer part of the tire that connects the tread to the rim; it does not directly interact with the road. The tread is the part of the tire designed with grooves and patterns that aid in traction and water drainage, but it's the contact patch that determines the section of the tire making that crucial connection with the surface. Finally, the rim is the metal part of the wheel that the tire is mounted on, which also doesn’t come in contact with the road itself. Understanding the role of the contact patch is important for safe driving practices and effective tire maintenance.