 |
||
4WD SUSPENSION
Page 3 of 7
Coil Springs
Coil springs and torsion bars operate in similar ways. A coil spring starts life as a torsion bar of much smaller diameter. As its name suggests, a coil spring is formed when a straight length of steel wire is wound into a coil. When a force is applied to the coil spring, the wire from which it is made twists along its own axis in the same way a torsion bar does. The steel wire’s resistance to twisting absorbs the force applied to it. Sometimes you hear of coil springs 'sagging’. This term refers to the wire in the spring having been twisted beyond its limits, which causes it to remain twisted after the load is removed. This means that the coil spring never returns to its original height and leaves the vehicle sitting lower than before, appearing to have sagged. This can occur because the spring is compressed too far when heavy weights are carried in a 4WD. Some springs are made from higher-quality steel than others, which can prevent them from sagging.
 |
GOOD POINTS
Coil springs are used on most modern 4WDs because they provide many advantages over leaf springs both on- and off-road. In off-road situations, coils are more inclined to allow articulation because they allow the laden wheel to move more freely up into the wheel arch, and they can bend sideways like a banana to let the opposing wheel move downwards. They lack the internal friction of leaf springs, allowing the shock absorbers to control spring movement effectively, which improves on-road and rough-road handling characteristics. Coil springs weigh very little and can be made in different diameters and lengths to suit various mounting applications.
 |
BAD POINTS
Coil springs lack the ability to locate the axle in any direction. Therefore, they must be combined with a series of linkages to attach the live axle or wheels to the chassis that take up space. Coils are load specific, which means they cannot vary their load-carrying capabilities like a leaf spring can. Therefore, each coil spring is only designed to carry a specific amount of weight. While variable-rate coil springs are available, they are impractical for passenger vehicle and off-road use. Should a coil spring break in the middle of nowhere, it is difficult get yourself out of trouble.
 |
