Lowering your car on an aftermarket coilover suspension system will give you a sporty, ground-hugging stance, while also improving all-around handling. However, the benefit of a coilover system over conventional spring/shock replacements is the coilover's adjustability. With a coilover system, you can custom tune your vehicle's ride height to whatever setting you wish. This lets you achieve both the perfect look for your car and the perfect suspension setting for your particular driving conditions.
Park your car on a flat, even surface. Raise each side of your vehicle with a floor jack, and support all four corners on jack stands. Remove the wheels, giving you access to the suspension components.
Disconnect the lower shock mount from the suspension control arm. Remove any suspension components restricting free-movement of the lower shock body, such as brake line mounts.
Use collar adjustment wrenches (supplied with most coilover sets) to loosen the lower shock body collar. The lower shock body can then be hand threaded up into the upper body. The further you thread the lower shock body upward, the greater the reduction in ride height.
Repeat Step 3 for all four coilovers. Ensure that you equally reduce the amount of ride height on each shock body to avoid an uneven vehicle stance and poor handling characteristics. Once all coilovers are set, replace all the suspension components removed for installation, as well as the wheels. Lower your vehicle off the jack stands.
Have your vehicle's suspension professionally aligned. Changing the ride height will effect other suspension attributes, such as camber and toe. These settings need to be realigned for optimum handling performance, as well as even tire wear.