Steering, Suspension and Braking Systems
Domain focus
Steering, Suspension and Braking Systems tests geometry, ride control, hydraulic braking, and inspection. Expect wheel alignment angles, spring and damper functions, brake bleeding, and ABS basics.
Core rules
- Camber is wheel lean viewed from the front; caster is steering-axis tilt viewed from the side; toe is the difference in front and rear distance between wheels. Incorrect toe scrubs tyres.
- The inner wheel turns more sharply than the outer wheel; this is steering geometry, often described through Ackermann principles.
- Springs support load; dampers control spring oscillation. Worn dampers cause bounce and poor tyre contact.
- Hydraulic brake force is multiplied by pedal leverage and piston area ratio. Air in the system compresses and gives a spongy pedal.
- Bleed from the wheel farthest from the master cylinder first, usually, and keep the reservoir topped up.
Worked example
A spongy brake pedal after pad replacement suggests air or a fluid leak. The reasoning: hydraulic fluid is nearly incompressible, but air compresses. Pressure-bleed the circuit in the specified order, check for leaks, then test the pedal before road test.
Traps
Mixing brake fluids, bleeding with an empty reservoir, confusing camber with caster, and moving the vehicle before pumping the pedal are mark-losing mistakes.