Suspension System Overview

The suspension system connects the wheels to the vehicle body and allows the wheels to move independently over bumps and through turns without the body moving with them. Without suspension, every irregularity in the road would be transmitted directly through the frame into the passenger compartment. The driver would not be able to maintain vehicle control over anything but a perfectly smooth surface.

Absorbs road impacts — bumps, potholes, and rough pavement hit the tire and wheel first. The suspension allows those wheels to move up and down, absorbing the energy before it reaches the body. Maintains tire contact — the tire can only generate traction, braking force, and steering response when it is in contact with the road. Suspension keeps the tire planted against the road through bumps and body roll. Supports the vehicle weight — springs carry the weight of the vehicle at all four corners. Provides steering and alignment — suspension geometry determines how the wheels are angled relative to the road and body.

Suspension noise diagnosis without a drive-on rack is guesswork. Components that produce noise and show movement under the full weight of the vehicle may show no perceptible movement at all with the wheels hanging free and unloaded. It is like trying to diagnose a squeaky chair while standing next to it instead of sitting in it. Put it on the rack. Load the suspension in its operating position. Observe what moves under operating conditions. Then diagnose.

Independent suspension — each wheel moves independently of the wheel on the other side. When the left wheel hits a bump, the right wheel is not affected. Used on most modern passenger vehicles for all four corners or at least the front. Solid axle or live axle — both wheels on an axle are connected. When one wheel hits a bump, the axle moves and the other wheel is affected. Still used on the rear of many trucks and some SUVs for load-carrying capacity.