Vehicle Ride Height
Vehicle riding height or ground clearance is a vital measurement that's checked before performing a wheel alignment. It affects the toe, caster, and camber angles. Measurements are taken with a tape measure or special tool from the ground to the fender well, bumper, control arm, etc. Check for manufacturer's specifications before taking the vehicle's height measurement.
Typically sagging coils, leaf springs, suspension airbags, or torsion bars are at fault. Check the control arm bushings for wear or damage before condemning any spring. Vehicle manufacturers have different specifications and techniques for measuring ride height. Usually, if the vehicle sags more than an inch from front to rear or side to side, it is out of specifications. Always check the sticker in the door frame for the correct tire size. A larger or smaller diameter tire also affects the curb ride height measurements.
Sometimes if the ride height is within a certain amount, a shim is used to restore the measurement to specifications. The shim increases the ride harshness and the chance of the spring bottoming out. When worn, it's always best to replace these springs in pairs.
Variable-rate springs provide a soft ride when traveling with light loads and a firmer ride when traveling with heavier loads by using springs of different thickness and spacing between coils. A linear spring is squarer and has equal spacing and thickness throughout.