The MacPherson strut is a type of car suspension system widely used in modern vehicles. It can be used for both front and rear suspensions, but is usually found at the front, where it provides a steering pivot (kingpin) as well as a suspension mounting for the wheel. Rear struts are sometimes called Chapman struts.
It consists of a small subframe or arm at the bottom which provides a bottom mounting point for the hub or axle of the wheel. This subframe provides both lateral and longitudinal location of the wheel. The upper part of the hub is fixed to the strut proper, which extends upwards directly to a mounting in the body shell of the vehicle. This type of suspension is only applicable to monocoque (unitary) body construction. The strut will usually carry both the coil spring on which the body is suspended and the shock absorber, which is usually in the form of a cartridge mounted within the strut. The strut also usually has a steering arm built in. It is because the whole assembly is very simple and can be preassembled into a unit that is has become almost ubiquitous with manufacturers.
In addition to its simplicity and low manufacturing cost, it has few vices in respect of handling. Its only real drawbacks are that it tends to transmit noise and vibration from the road directly into the body shell, giving higher noise levels and a "hard" feeling to the ride compared with systems such as double wishbones, and that an otherwise simple shock absorber replacement is relatively expensive. Hence the Manufacturers need to add extra noise cancellation mechanisms.
CAD diagram of a MacPherson Strut
The system was named after Earl S. MacPherson, an engineer who developed the design for the 1951 Ford Consul and later Zephyr.