Steering and Suspension Systems
Steering and suspension concepts
Candidates must understand steering geometry-toe, camber, caster, steering-axis inclination and thrust angle-and how each affects wear, stability and steering effort. Know common layouts: MacPherson strut, double wishbone, multi-link, live axle; springs, dampers, anti-roll bars, bushings, ball joints, tie rods and wheel bearings. Electric power steering adds motor, torque sensor and control module. Alignment is measured with the vehicle at correct ride height and tyre pressures.
Traps
Caster is a stability angle and generally does not cause tyre wear; toe causes feather-edged wear; camber causes one-shoulder wear. A pull can be caused by tyre conicity, brake drag or thrust-angle misalignment, not only camber. Do not diagnose a worn ball joint by prying against a plastic or aluminium component. Memory steer, off-centre steering wheel and returnability point to different causes. Checking wheel bearings requires attention to load: a bearing may be quiet unloaded and noisy when cornering.
Worked example
A vehicle pulls right and the right front tyre has a feathered inner edge. Check tyre pressures and rotate tyres first, then measure alignment. If total toe is outside specification but camber and caster are correct, adjust toe and re-centre the steering wheel. Rule of thumb: feathered tread = toe; smooth one-shoulder wear = camber; scalloped wear = damper or balance.
Exam approach
Separate tyre wear patterns from pulling complaints. Confirm with an alignment printout and a road test before replacing suspension parts.