Steering, Suspension and Braking Systems
Domain focus
This domain tests wheel alignment, steering geometry, suspension operation, and hydraulic braking performance. It links vehicle stability and stopping distance to measurable geometry and pressure values.
Core rules
- Caster, camber, toe, and kingpin inclination affect straight-line stability, tyre wear, and steering effort.
- Ackermann geometry allows inner and outer front wheels to follow different radii on a turn.
- Dampers control spring oscillation; worn dampers increase pitch, wheel hop, and stopping distance.
- Hydraulic pressure = force ÷ area. A larger caliper piston area increases clamping force at the same line pressure.
- ABS modulates brake pressure to prevent wheel lock, but it cannot exceed tyre-road friction.
Worked example
A 200 N pedal force acts through a 4:1 pedal ratio, giving 800 N at the master cylinder. With a 20 mm master-cylinder bore, area = π/4 × 0.020² = 3.142 × 10⁻⁴ m². Pressure = 800 ÷ 3.142 × 10⁻⁴ = 2.55 MPa. A caliper with a 50 mm piston has area 1.963 × 10⁻³ m², so clamping force = 2.55 × 10⁶ × 1.963 × 10⁻³ ≈ 5,006 N. The example shows why pedal ratio and piston area matter.
Traps
Using diameter instead of area, ignoring pedal ratio, and assuming ABS shortens every stop. Brake fade from heat, contaminated fluid, and incorrect tyre pressure can mimic hydraulic faults.