Automobile Suspension Design 101 (Part IV): MacPherson Strut Suspension

Now let’s take a look at the third type of automobile suspension: the MacPherson type system. For simplicity, you can consider the MacPherson suspension to be the double wishbone suspension with the upper A-arm replaced by a vertical strut, whose upper end is rigidly fixed to the car body’s strut tower.

In the following chart, the one highlighted as “Original” is the most original MacPherson suspension. Of course there are multiple variations. For example you can decompose the lower A-arm into two control arms, which is popular in some BMW and Mercedes-Benz lower-end models, for example the BMW E90 3-series (BMW called it to be “double-pivot”), and Mercedes-Benz’s C/E-classes (MB named it “3-link”).

The variation highlighted as “Variation 2” on the chart is similar to the one that we have just discussed described above (E90 3-series, MB C/E classes), but the decomposed two control arms are placed in parallel. This geometry setup is mainly for rear wheel suspension, and is commonly seen in many mainstream cars or even sports cars. Famous usages include Toyota Camry and Porsche Boxster/Cayman.

The advantages of MacPherson suspension are its simplicity and also low manufacturing cost. But this comes with expense that this design does not allow vertical movement of the wheel without some degrees of combination between camber angle change and sideways movement. With the same level or engineering, MacPherson suspension usually has inferior performance compared to double wishbone or multi-link suspensions.

In part V, we will examine the last type of suspension: the H-arm system.

Index:

Automobile Suspension Design 101 (Part I): What Is A Suspension?

Automobile Suspension Design 101 (Part II): Trailing Arm Suspension

Automobile Suspension Design 101 (Part III): Double Wishbone Suspension

Automobile Suspension Design 101 (Part IV): MacPherson Strut Suspension

Automobile Suspension Design 101 (Part V): H-Arm Suspension

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