Rear suspension - dependant systems

Contrary to the front version of this system, many many cars are still designed and built with dependant (linked) rear suspension systems.

Solid-axle, leaf-spring

This system was favoured by the Americans for years because it was dead simple and cheap to build. The ride quality is decidedly questionable though. The drive axle (purple in this image) is clamped (green) to the leaf springs (red). The shock absorbers (yellow) are also attached to the clamps. The ends of the leaf springs are attached directly to the chassis, as are the shock absorbers. Simple, not particularly elegant, but cheap. The main drawback with this arrangement is the lack of lateral location for the axle.

Solid-axle, coil-spring

This is a variation and update on the system described above. The basic idea is the same, but the leaf springs have been removed in favour of 'coil-over-oil' spring and shock combos. Because the leaf springs have been removed, the axle now needs to have lateral support from a pair control arms. The front ends of these are attached to the chassis, the rear ends to the axle. A variation on this has the shock absorbers separate from the springs, allowing much smaller springs. This in turn allows the system to fit in a smaller area under the car.

Beam Axle

This system is used in front wheel drive cars, where the rear axle isn't driven. (hence it's full description as a 'dead beam'). Again, it is a relatively simple system. The beam runs across under the car with the wheels attached to either end of it. Also at the ends, the springs and shock absorbers are attached. The beam has two integral trailing arms built in instead of the separate control arms required by the solid-axle-coil-spring system. Variations on this system can have either separate springs and shocks as shown here, or the combined 'coil-over-oil' variety. One noteable feature of this system is the track bar (or panhard rod). This is a diagonal bar which runs from the rear corner of the beam to a point either just in front of the opposite corner, or in this case, above the opposite spring mount. This is to prevent side-to-side movement in the beam which would cause all manner of nasty handling problems. A variation on this them is the twist axle which is identical with the exception of the panhard rod. In this system, the axle is designed to twist slightly. This gives, in effect, a semi-independent system whereby a bump on one wheel is partially soaked up by the twisting action of the beam. Yet another variation on this system does away with the springs and replaces them with torsion bars running across the chassis, and attached to the leading edge of the beam supports. These beam types are currently very popular because of their simplicity and low cost.

Rear suspension - independent systems

It follows, that what can be fitted to the front of a car, can be fitted to the rear to without the complexities of the steering gear. Simplified versions of all the independent systems described above can be found on the rear axles of cars. The multi-link system is currently becoming more and more popular. In advertising, it's put across as '4-wheel independent suspension'. This means all the wheels are independently mounted and sprung. There are two schools of thought as to whether this system is better or worse for handling than, for example, Macpherson struts and a twist axle. The drive towards 4-wheel independent suspension is primarily to improve ride quality without degrading handling.