Coil springs are helical mechanical devices storing potential energy to provide suspension and support vehicle weight. Typically implemented as part of a complete strut or shock absorber assembly, they are found on most modern vehicle suspension systems. Constructed of spring steel alloy, coil spring rate—measured in pounds per inch—dictates ride firmness and load-carrying capacity. Key characteristics include wire diameter, coil diameter, overall length, and free length, all influencing spring performance. Variations exist including linear, progressive, and dual-spring designs to optimize ride quality and handling characteristics.