Shocks Vs. Coilshocks

This "divorced" shock/spring package places the shock almost a foot from the spring.

Coilover shocks -- also called coilshocks -- have gotten a lot of press in recent years, and for good reason. The coilover takes all that's best about the standard coilspring and shock absorbers and combines them into a fully independent package that bolts on easily, adjusts quickly and maintains a consistent performance envelope.

Suspension Basics

A standard coilspring and shock -- or "divorced" -- package consists of a spring that suspends the car, and a separate shock absorber that controls the speed of suspension movement. This arrangement has been in use for decades, but it has lately been superseded by the coilover arrangement. A coilover is a coilspring with a shock absorber stuck through the center. A pair of caps on either end of the spring contain the shock absorber and serve as mounts to connect the coilover to the chassis.

Dynamics

The coilover's biggest advantage, dynamically speaking, is that the shock absorber and spring both act on the same plane of movement. If you place a spring over the axle or control arm and the shock absorber several inches away, the car's body and suspension will alternately try to pivot on either the coilspring or the shock absorber, depending upon the conditions. Spring rate, shock rate and chassis tuning are made much simpler and more predictable by using a coilover.

Adjustment

It's not impossible to adjust the ride height on a divorced spring-and-shock package, it's just a lot more difficult. The coilover connects at only two points: the through bolts that secure its end caps to the chassis and the suspension. A divorced coilspring sits flat on the control arm or axle and a pocket in the chassis. So, dropping the ride height on a coilover is just a matter of moving the end caps closer together by turning them downward on the threaded mounting rod. With a divorced coil/shock package, the only way to change ride height is to cut the springs, use different springs or install spring spacers.

Retrofitting Coilovers

Coilover retrofits are simpler on some chassis than on others. The main issue is usually that the coilspring itself just wedges in between the axle/control arm and chassis, which means that the vehicle lacks provisions for the coilover's through-bolt mounting system. A coilover conversion kit specifically designed for a particular vehicle should contain mounting plates for the coilovers, but those plates can take up space and reduce the suspension's range of movement. But the tradeoff is usually fairly minimal considering the coilover's inherent advantages.

References

• Chassis Tuning; Herb Adams
• Build Your Own Sports Car, On a Budget; Chris Gibbs