Vehicle Mechanics and Vehicle Dynamics
Mechanics essentials
Candidates should understand the main systems: engine and driveline, braking system (including ABS/EBS, retarders and air pressure), steering, suspension, tyres and electrical systems. Know the meaning of warning lamps and when a defect makes the vehicle unfit to drive. Pre-trip checks cover tyres (pressure, tread, damage), lights, brakes, fluids, mirrors and load security.
Vehicle dynamics
Key concepts are centre of gravity, weight transfer, understeer and oversteer, and the effect of load on handling. A high centre of gravity increases rollover risk in curves. On a bend, centrifugal force pushes outward; speed, curve radius and load height determine whether the vehicle stays upright. Braking transfers weight forward, reducing rear grip. Acceleration transfers weight rearward. Jackknifing in articulated vehicles results from drive-axle lock-up or trailer push during braking on low-grip surfaces.
Traps
- Believing a heavier load improves grip everywhere - it increases stopping distance and rollover risk.
- Confusing understeer (vehicle runs wide) with oversteer (rear steps out).
- Ignoring that ABS warning lamp means the system may be disabled.
- Forgetting that tyre underinflation causes heat build-up and blowouts.
Worked example
A tractor-semitrailer enters a curve too fast. The correct response is to ease off the accelerator smoothly and avoid harsh braking, which could lock wheels and cause a jackknife. Rule of thumb: slow in, steady through, accelerate gently out - and always reduce speed before the curve, not in it.