The strut on a car is a suspension component much like the shock absorber. However, it integrates other suspension components and when applied to the front suspension, it also integrates steering components.
The function of a strut on a car is to dampen the bouncing of the vehicle when it goes over uneven surfaces, much like a shock absorber. The shock absorber in a strut is merely one component of the strut.
The strut integrates other suspension components such as the coil spring and ball joint. Unlike a shock, the strut combines the coil spring, the upper and lower coil spring seats, the strut bearing and bearing plate, the steering knuckle with the lower ball joint and the shock absorber cartridge.
The strut was first developed in the mid 1920s and used on aircraft. It was introduced to vehicles in the late 1940s. The first car that used the strut was the Ford Vedette in 1949 on the front suspension. Most all-front-wheel-drive vehicles of today use at least front struts, but many use struts on all four corners of the vehicle.
A strut has a shock absorber cartridge that is contained inside the coil spring. It mounts to the steering knuckle at the base of the strut and then is attached to the top of the engine compartment through a strut tower. A close cousin to the strut is a coil-over shock, but the coil-over does not eliminate the presence of an upper control arm and upper ball joint.
As is the case with shock absorbers, after wear and tear and aging, the strut weakens. This can cause serious side effects such as tire wear, poorer rebound effects and a lack of steering stability. The strut should be checked periodically for signs of weakening and failure.
