Steering, Suspension and Braking Systems
Steering, Suspension and Braking Systems
This domain tests how a vehicle is controlled, kept stable and stopped safely. Expect steering ratio, wheel alignment angles, suspension components, shock absorber action, hydraulic brake operation, brake fade and ABS basics.
Core rules
- Steering ratio = steering wheel rotation ÷ road-wheel angle. A higher ratio reduces effort but slows response.
- Alignment: camber is the inward or outward tilt of the wheel in front view; caster is the steering axis tilt in side view and provides self-centring; toe is the difference in front and rear of the wheels.
- Suspension springs support weight; shock absorbers damp spring oscillations. Independent suspension reduces unsprung mass and improves ride.
- Hydraulic brakes multiply pedal force through piston area ratio. Brake fade is loss of friction from heat; bleeding removes air from the hydraulic circuit.
Worked example
A steering wheel is turned through 360° and the road wheel moves 20°. Steering ratio = 360 ÷ 20 = 18:1. Reasoning: the ratio compares input rotation with output angle. It is not a gear tooth ratio, and a larger number means more driver effort is reduced but steering response is slower.
Traps
- Confusing camber with caster; caster affects straight-line stability, camber affects tyre wear and cornering.
- Bleeding brakes in the wrong order or allowing the reservoir to run dry.
- Thinking ABS shortens every stop; it mainly preserves steering control during hard braking.
- Describing shock absorbers as load-carrying springs.