Sprung mass refers to vehicle parts supported on the springs, such as the body, frame, and engine. Unsprung mass includes parts of the steering and suspension not supported by springs, such as wheels, tires, and brake assemblies.
Leaf springs absorb applied force by flattening out under load. Coil springs absorb force of impact by twisting. Torsion bars twist around their center.
Driving thrust, braking torque, and cornering force operate to displace wheel units. These forces must be transferred to the vehicle frame, but the wheel units must stay aligned with each other, and with the frame.
