What Is the MacPherson Strut?

Different cars have different types of suspensions, and you're probably aware of some of them. But in your car shopping, have you come across the term 'MacPherson Strut?' A strut is a type of car suspension system, but what's peculiar about the MacPherson type is why many carmakers make it a point to make sure you KNOW they're using it and not just another strut type. So what makes it so special?

The MacPherson Strut defined

A MacPherson Strut is a type of suspension that combines two main functions--as steering rod and as a suspension/vibration dampener. In old systems, these functions were performed by two separate parts. With the MacPherson Strut, both functions are done by a single component. This simplification makes the MacPherson Strut less expensive than other systems to incorporate into a car.

History of the MacPherson Strut

The MacPherson Strut was developed by American automotive engineer Earle S. MacPherson back in the late 1940s. His version of the strut is largely influenced by the designs by Guido Fornaca, his peer/rival who worked at FIAT, and Cottin-Desgouttes, a French automaker that employed a leaf-spring-based design that unified the steering rod and suspension into one. Using these earlier designs as inspiration, MacPherson began to develop his own system in the 1940s, utilizing a singly assembly coil spring and shock absorber.

The first car to feature MacPherson's invention was the 1949 Ford Verdette, followed by the Ford Consul and Zephyr, both released in 1951. MacPherson initially incorporated his invention in both front and rear wheels, but because of the inclusion of the steering rod, it has more practical operations for the front only. Most cars today usually have a front MacPherson strut front and torsion beam rear suspension pairing, although a rear MacPherson can still be found in some cars.

How does it work?

The MacPherson system can use either a steering knuckle or hub carrier with two mounting points--one at the top and one at the bottom--that bolt to the body of the vehicle. The lower mounting point links to a track control arm, which operates both the longitudinal and lateral direction of the wheel assembly. The upper mounting point, on the other hand, links to a coil spring, shock absorber, or both.

The two mounting points, together with the knuckle or hub joint, make the MacPherson strut into a sturdy yet versatile three-point support structure for both the wheel and the car body that can easily be customized to more demanding usage, whether it be for hauling cargo or racetrack driving.

Advantages and Disadvantages

The simplicity of the MacPherson strut is its main advantage. By eliminating the need for a separate upper control arm, the MacPherson strut requires less components to produce, which makes them cheaper to make, more lightweight, and smaller than other types of suspension systems. The last two benefits mean MacPhersons take up less space without adding too much to a car's heaviness.

Unfortunately, simplicity is also MacPherson's biggest drawback. The manner in which it's bolted to the body--where the axis connects straight down to the wheel--doesn't dampen vibrations very well. However, this can be softened by bushings and the support of other mechanisms and components.

The same simplicity in its construction also means that the camber angle shifts along with the vertical position of the wheel when it turns. This can hamper a car's handling, which makes the MacPherson strut more inferior to advanced suspension systems, such as double wishbone.

Nevertheless, the MacPherson Strut remains a remarkable invention, effectively combining strength, support, and stability, all at a suitably low manufacturing cost.