For something so simple--the combination of a coil spring and a dampening shock--it took the auto industry nearly 60 years to come up with it. Since then, the MacPherson strut has been used on hundreds of different cars from Peugeot to Volkswagen and has since become one of the dominating suspensions systems of the world because of its compactness and low cost.
Similar to a double wishbone suspension, MacPherson struts can be adopted for both front- and rear-wheel use, and in the 1980s, many budget cars employed a MacPherson strut on each corner. Such cars as Fiat's Type 4 and Tipo platforms on which Fiat Croma, Lancia Thema, Saab 9000, Fiat Tipo, Tempra, Lancia Delta and Dedra were based (to name a few European models). Though none of these are particularly famous for their handling characteristics, by contrast MacPherson struts can be found on both the Audi Quattro Coupe and the Subaru Impreza, both known for their zoom.
Earl Steele MacPherson was born in Britain, worked in France for an American company and produced a product that would later affect a German car. He was a well-known General Motors engineer for Chevrolet, and after moving to Ford's European division, he developed the strut that would bear his name. It was first adopted on the French Ford Vedette in 1949. Two years later, Ford in Britain used it for the Consul and the Zephyr, but in 1954, Ford sold its French line to Simca. The Peugeot first used the MacPherson on the 404 in 1960, and most small cars nowadays employ the strut in some fashion. And here you thought it was just a Type IV and Super Beetle thing, right?
In their most basic forms, suspensions are designed to deal with bumps in the road to enhance the comfort of the ride. When the car hits a bump, and it does so hundreds of times a minute, the springs are compressed and the energy is absorbed, but since they are simply springs, they return that energy quickly. Dampers (the struts inside the coil springs) slow down this quick bouncing motion and smooth out the ride. Studies on automobile comfort have shown that humans perceive more than two Hertz of bouncing frequency (or two bounces per second) as uncomfortable, and these dampers control that frequency to approximately one to 1.5 Hertz.
More important than controlling bounce frequency, suspensions were created to allow the wheel to move independent of the car's body. Of course, in doing so, this creates many problems, most notably is body roll, or weight transfer toward the outside wheels in a turn. This weight transfer also changes the camber of the wheels (when a wheel isn't perpendicular to the road and the direction of travel, it has a camber, a positive or negative angle), which leads to under- or over-steer, and if you brake during the turn, you are affecting the castor angles as well. Without all of the automotive terms here, you're screwing up your tires, reducing the safety of the car's ability to stay on the road and causing a lot of stress on the wheels and suspension parts.
The most unique feature of a MacPherson strut suspension is that all of the components are contained in a single assembly. Based on a triangle design, a typical MacPherson strut assembly includes a coil spring, upper suspension locator and shock absorber and is mounted between the arm of the steering knuckle and the inner fender panel.
The strut is the heart of the MacPherson suspension system. Not only do struts look like conventional shock absorbers, they also perform the same shock-dampening function. They reduce suspension space and weight requirements as well; by mounting the strut assembly to the steering knuckle, the need for an upper control arm and ball joint is eliminated. The upper mount is the load-carrying component on MacPherson suspensions.
Since the strut is vertically positioned, the whole suspension is very compact. It combines the use of the damper and the coil spring as the pivot point for the wheels to steer, while the strut itself is the load bearing member of the assembly, holding up the weight of the car. This system has good road-holding capabilities for a very reasonable price, which is probably the reason why it is one of the most popular suspension system in the world.
The MacPherson strut suspension system is unlike any other design because the telescopic shock absorber also serves as a link to control the position of the wheel. The steering is, on a Volkswagen at least, connected to an arm from the back of the spindle. When you steer, it physically twists the unit as the wheel turns.
Since many cars makers obviously don't want to pay Ford royalties for each one used (they own the patent; they get a percentage of sales), there are now so many variations of the basic strut system around today. Porsche, Audi, Volkswagen and many others have variations on the MacPherson Strut in use, and though it was once found almost exclusively on foreign cars, the MacPherson strut suspension system is now used on a large (and growing) number of American models as well.
The design, however, does not offer perfect handling, and its drawbacks are just as important as its attributes. Body roll and wheel movement lead to variation in camber, although not as severe as the swing axle suspension. From a sports car enthusiast's point of view, its relatively high overall height requires a higher hood line to accommodate the length of the strut, which is not very desirable to sports cars' styling. All in all, from the Type IV (the first VW to use the MacPherson strut) in 1968 to the Super Beetle and its Convertible counterpart in 1979, Volkswagen employed the famous system for 11 years. There you have it. And you said you weren't going to learn anything today.