Braking, Steering and Suspension Systems
What this domain tests
This domain covers hydraulic braking, ABS, drum and disc service, steering geometry, steering systems and suspension layouts. Questions target bleeding order, brake fluid, pad and disc limits, camber, caster, toe, and correct diagnosis of pull, vibration and noise.
Core rules
- Brake fluid is hygroscopic. DOT 3 and DOT 4 absorb water, lowering the boiling point, so replacement is typically every two years.
- Bleed from the wheel farthest from the master cylinder: right rear, left rear, right front, left front, keeping the reservoir topped up.
- Front pads are commonly condemned near 2 mm; disc runout limits are around 0.05 mm. Measure with a dial gauge.
- Alignment order is rear first, then caster and camber, then toe last, with the vehicle at kerb weight.
- Suspension bushes are tightened at normal ride height, otherwise they tear.
- Camber is the wheel's tilt from vertical, caster is the steering axis tilt, toe is the difference in track between front and rear of the wheels.
Worked example
A car pulls right. Left camber reads -0.5° and right camber reads +0.4°, so cross camber is 0.9° against a 0.5° limit. The car drifts toward the side with the more positive camber, that is, to the right. Before adjusting, swap the front tyres and road test, because a conicity fault in a tyre produces the same pull. If the pull follows the tyre, the alignment is not the cause.
Traps that cost marks
- Letting a caliper hang by its hose, which damages the internal reinforcement.
- Prying rubber bushes with a bar during inspection.
- Adjusting toe before camber and caster.
- Pumping an ABS system without following the scan-tool bleed procedure.