A type of spring made of wound heavy-gauge steel wire used to support the weight of the vehicle. A Coil springs, also known as a helical spring, is a mechanical device, which is typically used to store energy and subsequently release it, to absorb shock, or to maintain a force between contacting surfaces. The spring may be located between the control arm and chassis, the axle and chassis, or around a MacPherson strut. Coil springs may be conical or spiral wound, constant rate or variable rate, and wound with variable pitch spacing or variable thickness wire. Coil springs sag with age, and sometimes break. Replacement in pairs is recommended to maintain even ride height side-to-side. Together with a shock absorber, coil springs are pre-assembled as one coil over unit before installation. While the coil spring compresses and stretches to keep you safe as you drive, the shock absorber keeps you from road noise, bumps, and vibrations that you might encounter while doing so. All in all, a coil over is essential in your vehicle’s suspension because it gives you optimal damping, good handling and braking, and a comfortable ride all at the same time.