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SKM Motor Vehicle Mechanic Level 3 study materials
SKM Motor Vehicle Mechanic Level 3 study resources

SKM Motor Vehicle Mechanic Level 3: Chassis, Steering, Suspension, and Braking Systems

SKM Motor Vehicle Mechanic Level 3 · Work through your exam, one topic at a time.

All guide sections

Chassis, Steering, Suspension, and Braking Systems

What this domain tests

This domain tests steering, suspension, wheel alignment, tyres and braking. You must be able to read alignment angles, test brake hydraulics and identify wear in joints and bearings before it becomes a safety failure.

Core rules

  • Alignment order matters: check tyre pressures and ride height, then rear camber and toe, then front camber and caster, then front toe last.
  • Camber is the inward or outward tilt of the wheel; caster is the steering-axis tilt; toe is the difference between front and rear of the wheels. A pull can come from tyre conicity, brake drag or a caster difference, not only from toe.
  • Brake fluid is hygroscopic. Use the specified DOT grade, never mix DOT 5 silicone with DOT 3/4, and bleed in the manufacturer's sequence, usually starting at the wheel farthest from the master cylinder.
  • Measure disc thickness with a micrometer at several points, and disc runout with a dial gauge on a cleaned hub. A pulsating pedal often comes from thickness variation, not a warped disc.
  • Minimum tyre tread is 1.6 mm; check for uneven wear, cracks and correct torque.
  • After alignment or steering-angle sensor work, reset the SAS and check ADAS calibration if fitted.

Worked example

A car has a pulsating brake pedal and steering-wheel shake under braking. The front discs are measured with a micrometer: one disc varies from 24.8 mm to 24.5 mm, and runout is 0.09 mm. The hub face has rust and debris. The reasoning is that thickness variation and runout are transferring pulsation through the caliper. The repair is to clean the hub, replace or resurface the discs within the minimum thickness, fit new pads, and torque the wheels evenly. Merely replacing pads would not cure the pulsation.

Traps

Measuring a disc with a caliper is not accurate enough. Fitting new pads on scored or below-minimum discs is a comeback. Do not forget to clean the hub face. Mixing brake fluid grades or leaving the reservoir cap off can cause contamination. Do not test-drive a car with a known brake fluid leak.