COIL SPRING SUSPENSION
What: In a coil spring suspension system, the steering knuckle and wheel spindle assembly is connected between upper and lower control arms. The control arms are connected to the vehicle frame, and the coil spring is positioned either between the upper control arm and the vehicle's body or between the lower control arm and the vehicle frame.
How: In either case, a shock absorber dampens the up and down oscillations of the spring. The weight of the front half of the vehicle rests upon the coil springs.
The ball joints connect the steering knuckle to the control arms, allowing the steering knuckle to pivot between the control arms when the vehicle is steered.
They also permit up and down movement of the control arm. One ball joint is called the load carrier and the other is called the follower. Which is which depends on the location of the shock and spring. When the shock and spring are positioned between the lower control arm and the frame, the lower ball joint is the load carrier. When the shock and spring are connected between the upper control arm and the vehicle body, the upper ball joint is the load carrier. In both cases, the weight of the vehicle is transmitted through the spring to the control arm at its bottom...and through the control arm to the load carrier ball joint. Load carrier ball joints bear approximately one-half of the total vehicle weight. They are subjected to severe wear and it is important to periodically inspect them. Conventional shock absorbers, on the other hand, do not carry weight.