Suspension Systems
Types and Load Paths
Suspension questions test whether you know where the weight goes. On a MacPherson strut, the strut carries the spring load and the lower ball joint is typically load-bearing (axial). On a short-long arm design the spring sits on the lower control arm, so the lower joint is load-bearing and the upper is a follower. Solid axles use leaf or coil springs with control arms and a track bar; independent rear suspensions often use multilink layouts with separate links setting camber and toe.
Wear Items and Diagnosis
Coil springs sag and change ride height, which shifts camber and caster. Torsion bars are adjusted at the anchor and can be re-indexed. Sway bar links and bushings clunk over bumps or while turning; torn control arm bushings cause wander and memory steer. Struts and shocks are diagnosed by oil leakage, tire cupping, floating over dips, and excessive body motion - the old bounce test is unreliable on gas-charged units.
The Big Trap
Checking ball joints with the suspension hanging is the classic error. Follow the manufacturer's procedure: many lower joints must be checked at ride height with the joint unloaded by prying under the tire, while others require a dial gauge. Vertical play on a loaded joint can be invisible.
Worked Example
A vehicle clunks over bumps with uneven front tire wear: check sway bar links with the suspension loaded, then check the strut mount bearing by turning the wheel and feeling for bind. Replace in pairs on the same axle when the opposite side shows similar wear.