What often gets overlooked is the shocks and struts (dampers) and how lowering springs affect their performance and fit. Each damper has a specific travel length which is matched with the spring rate of the car's O.E. springs. When you install shorter springs, the O.E. damper may "bottom out" and become damaged. For this reason, it is recommended to match your new shorter "sport" springs with the correct "sport" dampers. To better understand dampers, take a look at our tech article titled "Damper Dynamics."
One way to ensure that your new sport springs will match the performance of your new dampers is to purchase a spring/damper kit. These kits are engineered to provide optimal spring rate and dampening stiffness for your vehicle which takes out some of the guesswork in matching your suspension components.
For more information on lowering, read "A Look at Lowering."