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Which forces in an automobile depend on friction?

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A diagram displays six types of simple machines with labeled illustrations: inclined plane, wedge, screw, lever, wheel and axle, and pulley, each shown with real-world examples like ramps, axes, screws, seesaws, door handles, and pulleys lifting objects. — machine Six simple machines for transforming energy into work.

In an automobile, friction is a fundamental force that is essential for both vehicle control and the operation of various mechanical systems. While friction is often viewed as an undesirable force that consumes engine power in moving parts, it is also a critical requirement for the following functions:

Traction and Braking: Friction between the tires and the road surface is necessary to provide the traction required for movement. Similarly, brakes rely on friction between stationary elements (such as pads or shoes) and rotating components (drums or disks) to dissipate kinetic energy and stop the vehicle.12
Power Transmission: Friction is vital for the operation of the clutch, which connects the engine to the transmission. Additionally, belts used to drive accessories like the fan and generator are friction-dependent devices.2
Stepless Transmissions: Certain types of transmissions, such as those using V-belts or rolling-contact bodies (traction drives), rely directly on friction to transmit power and modify speed ratios.3

While lubrication is used to minimize friction in engines and bearings to improve efficiency, these systems remain inherently dependent on the controlled application of frictional forces to perform their intended tasks.2