Independent Suspension System Basics
Your car’s independent suspension system looks quite a bit different from how the first automotive chassis were designed. Over the years, the desire to improve handling, comfort and reduce weight has lead to advances in suspension design that are now nearly standard across the industry. Not all cars benefit from fully independent suspensions at all four corners, but you’d be hard-pressed to find one without this type of technology up front.
Originally, almost every vehicle employed a solid axle at the front and rear connecting the wheels on either side. This was great for strength — and, in fact, some dedicated off-road rigs still use solid front axles — but it required a lot of compromises when it came to dealing with bumps and steering. Since the wheels couldn’t move independently of each other, a pothole encountered by one front wheel also disturbed the other, and turn radius was restricted by the wheels binding when asked to move in tight quarters.
MacPherson to the Rescue
At the end of the 1940s, General Motors developed the MacPherson strut, named after its inventor. By combining a coil spring and a shock absorber together, it was possible to give each individual wheel its own suspension travel without sacrificing strength. This meant no more need for leaf springs or solid axles up front, and eventually, the change spread to the rear of the vehicle too. Of course, not all vehicles went the MacPherson route. The use of a pair of “A-arms” that resemble wishbones (one on top, the other on the bottom) to connect the wheel to the chassis became popular, with a shock and spring controlling movement and multilink setups to control the rear wheels are also common.
Variations on a Theme
While front suspension setups are almost always fully independent, history is littered with examples of semi-independent designs. Some vehicles employ torsion-beam or twist-beam rear suspension systems, which are inexpensive and space-saving ways to gain some of the benefits of a truly independent suspension system, without the full performance offered by a MacPherson or double-wishbone design. Other trailing arm designs and even De Dion tubes, which were most recently used by the Smart Fortwo, can also be found on older model vehicles. Finally, trucks still rely on solid rear axles, as they are a strong and inexpensive solution to dealing with heavy cargo and trailer weights.
Check out all the steering and suspension parts
Photo courtesy of Wikimedia Commons.