The strut is a common damper type used on many of today’s independent suspension, front wheel drive vehicles as well as some rear wheel drive vehicles.
A strut is a major structural part of a suspension. It takes the place of the upper control arm and upper ball joint used in conventional suspensions. Because of its design, a strut is lighter and takes up less space than the shock absorbers in conventional suspension systems. Struts perform two main jobs. First, struts perform a damping function like shock absorbers. Internally, a strut is similar to a shock absorber. A piston is attached to the end of the piston rod and works against hydraulic fluid to control spring and suspension movement. Just like shock absorbers, the valving generates resistance to forces created by the up and down motion of the suspension. Also like shock absorbers, a strut is velocity sensitive, meaning that it is valved so that the amount of resistance can increase or decrease depending on how fast the suspension moves.
Struts also perform a second job. Unlike shock absorbers, struts provide structural support for the vehicle suspension, support the spring, and hold the tire in an aligned position. Additionally, they bear much of the side load placed on the vehicle’s suspension. As a result, struts affect riding comfort and handling as well as vehicle control, braking, steering, wheel alignment and wear on other suspension
Typically, struts consists of a coil spring to support the vehicle’s weight, a strut housing to provide rigid structural support for the assembly, and a damping unit within the strut housing to control spring and suspension movement. The bottom of the strut body attaches to the steering knuckle, which in turn connects to a lower control arm through a lower ball joint.