The coil spring is the most common type of spring in passenger cars. It is simply a spring steel rod wound into a coil.
A coil spring shock. Courtesy of Tenneco Automotive, Inc.
Chassis Height Specifications
A quick overall visual inspection detects any obvious sag from front to rear or from side to side. Under the car, at the level of the two ends of the control arms, check for out-of-level, damaged, or worn rubber bumpers, or shiny or worn spring coils. All indicate weak coil springs. Coil springs must be replaced when they have sagged beyond specifications. A more accurate inspection reveals less obvious problems by measuring heights at specific points on each side of the suspension system.
For the most accurate measurement of chassis height, use the service manual to check against the manufacturer's recommendations for the specific model. when performing a coil spring test to check a vehicle's ride height, you need to be careful. the measurement points vary from one model of vehicle to another, even amongst vehicles manufactured by the same company. when coil spring wear is suspected, it might be necessary to load the vehicle to the manufacturer's suggested capacities and measure at the designated points.