What do the tyres, steering and suspension do, and what makes a tyre legal and safe?
The jobs of the tyres (grip, tread depth and pressure, the legal minimum), the steering system, and the suspension that gives a smooth, controlled ride.
A CCEA GCSE Motor Vehicle and Road User Studies answer on tyres (grip, tread depth, pressure and the legal minimum), the steering system, and the suspension that gives a smooth, controlled ride.
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What this dot point is asking
CCEA wants you to explain the jobs of the tyres (grip, tread, pressure and the 1.6 mm legal minimum), the steering system, and the suspension. The practical riding activity also checks steering and suspension movement, and tyre condition is checked at the MOT, so this content links the engine module to maintenance and safety.
The answer
Tyres
Tyres are the only contact between the car and the road, so they are vital for grip, braking, steering and a comfortable ride.
Steering
The steering system lets the driver control the direction of travel by turning the front wheels.
- Turning the steering wheel turns the steering column, which moves a mechanism (commonly a rack and pinion) and the track rods to turn the wheels.
- Power-assisted steering (PAS) uses hydraulic or electric assistance to make turning easier, especially at low speed.
- Wheel alignment (tracking) must be correct, or the car pulls to one side and the tyres wear unevenly.
Suspension
The suspension system supports the vehicle's weight and absorbs shocks from bumps in the road.
- Springs (coil or leaf) take up the bumps.
- Shock absorbers (dampers) stop the car bouncing up and down after a bump.
Worked example: a tyre check before a journey
Examples in context
Example 1. Wet-weather grip. Deep tread channels water away, so a tyre with good tread keeps grip in rain, while a bald tyre aquaplanes and skids.
Example 2. A bouncy car. A car that keeps bouncing after a bump has worn shock absorbers, which reduces grip and makes braking and steering less safe.
Try this
Q1. What is the legal minimum tread depth for a car tyre? [1 mark]
- Cue. 1.6 mm.
Q2. What is the main job of the steering system? [1 mark]
- Cue. To let the driver control the direction of the vehicle (turn the front wheels).
Q3. Name one part of the suspension system. [1 mark]
- Cue. Springs or shock absorbers (dampers).
Exam-style practice questions
Practice questions written in the style of CCEA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
CCEA style4 marksExplain why correct tyre tread and pressure are important for safety, and state the legal minimum tread depth for a car tyre.Show worked answer →
The tread channels water away from the contact patch so the tyre keeps grip on a wet road and avoids aquaplaning (skating on a film of water). Worn tread gives poor grip and longer braking distances. Correct tyre pressure keeps the right area of tyre in contact with the road for good grip, braking, steering and even wear, and saves fuel; under- or over-inflation reduces grip, increases wear and can cause a blow-out.
The legal minimum tread depth for a car tyre is 1.6 mm, across the central three-quarters of the tyre and around its whole circumference.
Markers reward: tread clears water/keeps grip (avoids aquaplaning), correct pressure for grip/braking/wear/economy, and the 1.6 mm legal minimum.
CCEA style4 marksDescribe the purpose of (a) the steering system and (b) the suspension system, and give one example of a part in each.Show worked answer →
(a) The steering system lets the driver control the direction of the vehicle by turning the front wheels in response to the steering wheel. An example part: the steering wheel, steering column, rack and pinion or track rods. Many cars have power-assisted steering to make turning easier.
(b) The suspension system supports the vehicle and absorbs shocks from bumps in the road, giving a smooth, comfortable ride and keeping the tyres in contact with the road for grip and control. An example part: the springs and the shock absorbers (dampers).
Markers reward: steering controls direction (with a named part), suspension absorbs shocks/keeps tyres on the road (with a named part such as springs or shock absorbers).
Related dot points
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A CCEA GCSE Motor Vehicle and Road User Studies answer on braking: the hydraulic system, disc and drum brakes, the handbrake, ABS, and how friction turns kinetic energy into heat to stop the car.
- The transmission system - clutch, gearbox, propeller/drive shaft and differential - and why a vehicle needs a clutch and a range of gears.
A CCEA GCSE Motor Vehicle and Road User Studies answer on the transmission system: the clutch, gearbox, drive shaft and differential, and why a vehicle needs a clutch and different gears.
- The dangers of excessive speed, the make-up of the overall stopping distance as thinking distance plus braking distance, and the factors that affect each.
A CCEA GCSE Motor Vehicle and Road User Studies answer on why speed is dangerous, how overall stopping distance is thinking distance plus braking distance, and the factors that affect each part.
- Routine driver safety checks (the FLOWERY checks), regular servicing, and why keeping a vehicle roadworthy is both a safety need and a legal duty.
A CCEA GCSE Motor Vehicle and Road User Studies answer on routine safety checks a driver should make, regular servicing, and why keeping a vehicle roadworthy is both a safety and a legal duty.
Sources & how we know this
- CCEA GCSE Motor Vehicle and Road User Studies specification — CCEA (2017)
- nidirect - tyres and the law — nidirect (NI Government) (2024)