Coil Springs -- connect a vehicle to its wheels. They also support your car and absorb the motion of the wheels by their constant compressing and expanding. Springs wear over time by losing their elasticity at which point the vehicle tends to sag losing its height profile. Or, when the vehicle does not sit level a broken spring is a possible cause. Either condition requires replacement.
Shocks absorber -- function to stabilize the vehicle any time it is disturbed such as going over bumps, holes, cornering, or stopping. Good shocks dampen the motion and energy potential of the springs and provide a smooth ride while minimizing spring bounce and keeping the wheels in contact with the road. Signs of wear are leaking oil along the shock body, broken mounts or mounting hardware, worn, missing bushings, cupped tire wear, excessive vehicle bounce, and hard leaning while the vehicle is cornering. Inferior shocks produce a hard ride.
Lower/Upper Control Arms -- join the wheel hub to the vehicle frame allowing for a full range of motion while maintaining proper suspension alignment. Signs of wear include uneven tires, suspension noise, misalignment, steering wheel shimmy, and vibration.
Half-Shaft -- holds the control arm bushings and provides an isolated and cushioned link between the control arms and the chassis. Signs of wear are excessive steering play, hard steering, irregular tire wear, front-end noise and shimmy.
Tie Rod -- The tie rod transmits force from the steering center link or the rack & pinion gear to the steering knuckle. This force causes the front steering wheels to turn left or right. The outer tie rod end connects to an adjusting sleeve, which allows the length of the tie rod to be adjusted. This adjustment is used to set a vehicle's alignment angle. Worn tie rods cause wandering, erratic steering, and major tire wear.