A basic understanding of the terminology and components associated with your car’s suspension system will allow you to diagnose problems and plan upgrades with more confidence and accuracy.
Springs determine the ride height of the vehicle, absorb bumps and imperfections in the road’s surface and govern the overall handling balance and ride quality. Coil springs are the most common type of spring for passenger vehicles, while leaf springs are typically found on trucks and SUVs. Springs with a shorter overall length and higher spring rate are commonly used to lower a car for a more aggressive stance and better handling.
Shock absorbers, struts, dampers and dashpots are all names for parts with the same basic function: converting the kinetic energy of the suspension into heat by forcing hydraulic or pneumatic fluid through a series of valves inside the body of the shock. Shocks control unwanted suspension motion and keep the tires in contact with the road surface. Along with springs, dampers have a huge effect on the overall ride quality and must be correctly matched to your spring rates, depending on the required handling characteristics.
The main function of a bump stop is to prevent your tire from contacting the body or frame of your car during any upward motion; in many modern designs, the bump stop also acts as an additional spring by employing a urethane material to even out the transition to full spring compression.
The term coil-over is thrown around a lot when talking about upgrading a car’s suspension. In many cases, it is simply used to designate a spring with an adjustable perch or collar that allows you to raise or lower a vehicle on the fly. A true coil-over refers to a matched spring and damper assembly with an integrated bump stop, often with adjustable upper mounts for precise suspension tuning.
Anti-roll bars or sway bars connect the left and right suspensions (either front, rear or both) to the frame in order to adjust the handling balance of the vehicle and limit the amount of sway or body roll under cornering. A heavier or larger diameter bar will provide more rigidity than a smaller one.
A popular suspension upgrade is a strut tower bar or brace, although some cars come equipped with one from the factory. An upper front strut bar is the most common type you see; this piece ties the shock mounting towers under the hood together, improving turn-in, steering response and overall chassis rigidity.