1. What is the main function of a road wheel on a motor vehicle?
To store fuel for the engine
To support the vehicle's weight and transmit driving, braking and cornering forces to the road
To act as the vehicle's primary electrical ground
To control the engine speed directly
Explanation:
Road wheels carry the vehicle load and transfer forces between the tyre and road so the vehicle can move, stop and turn.
2. What does the tyre marking 175/70 R14 tell you?
Tyre pressure 175 kPa, tread depth 70 mm, rim type R14
Tyre width 175 cm, rim diameter 70 inches, radial tyre, 14 ply
Tyre width is 175 mm, aspect ratio 70%, radial construction, rim diameter 14 inches
Maximum speed 175 km/h, 70 kg load index, rim size 14 mm
Explanation:
Tyre codes show width in millimetres, height as a percentage of width (aspect ratio), construction (R = radial) and rim diameter in inches.
3. Which of these is a common effect of driving on underinflated tyres?
Permanent increase in tyre diameter
Instant improvement in braking distance on wet roads
Higher fuel consumption, increased tyre wear and risk of overheating
Automatic self-repair of small punctures
Explanation:
Underinflated tyres flex more, causing extra rolling resistance (higher fuel use), uneven wear and heat build-up which can lead to tyre failure.
4. What is the minimum legal tread depth commonly required for passenger cars (in many countries including Kenya)?
0.5 millimetres
5 millimetres
10 millimetres
1.6 millimetres
Explanation:
Most vehicle regulations set a minimum tread depth around 1.6 mm for safety; shallower tread reduces grip and increases stopping distance.
5. What is the main purpose of wheel balancing?
To change the tyre compound for better grip
To permanently increase tyre tread depth
To align wheel camber automatically
To eliminate vibrations by making the wheel and tyre assembly have even weight distribution
Explanation:
Balancing adds small weights to offset heavy spots so the wheel turns smoothly without causing vibration at speed.
6. What does wheel alignment primarily correct?
The thickness of brake pads
The engine ignition timing
The tyre pressure automatically
The angles of wheels (toe, camber, caster) so tyres run straight and wear evenly
Explanation:
Proper alignment sets wheel angles to manufacturer specs, improving handling and preventing uneven tyre wear.
7. Why is tyre rotation (moving tyres between positions) recommended?
To make the tyre wider
To change the tyre's speed rating
To even out tyre wear and extend tyre life
To increase the tyre's legal load index
Explanation:
Different positions on the vehicle cause different wear patterns; rotating tyres periodically helps them wear more evenly.
8. What is the main difference between tubeless and tube tyres?
Tubeless tyres form an airtight seal with the rim and do not use a separate inner tube
Tube tyres can only be used on bicycles
Tube tyres are filled with metal instead of air
Tubeless tyres cannot be repaired after a puncture
Explanation:
Tubeless tyres seal directly against the rim, whereas tube tyres have an inner tube holding the air inside the tyre.
9. Which valve type is most commonly used on car tyres for inflation and pressure checks?
Bayonet valve
Presta valve
Schrader valve
Needle valve
Explanation:
Most passenger cars use the Schrader valve (a sturdy, spring-loaded valve) for tyre inflation and pressure measurement.
10. A worn wheel bearing is likely to produce which symptom?
Flickering dashboard lights
A humming or growling noise that changes with vehicle speed
A sudden drop in engine oil level
The brakes locking permanently
Explanation:
Failing wheel bearings often make a continuous noise that gets louder or changes pitch with speed and may show play in the wheel.
11. Why must you use the vehicle manufacturer's recommended jacking points when lifting a car?
To reset the wheel alignment
To avoid damaging the body or chassis and to lift the vehicle safely
So the engine will not overheat
Because any other point will automatically deflate the tyres
Explanation:
Using correct jacking points prevents crushing or bending components and ensures the vehicle is stable while lifted.
12. What is the correct way to tighten wheel nuts when fitting a wheel?
Tighten in a star or crisscross pattern to seat the wheel evenly
Tighten only one nut and drive a short distance
Leave nuts finger-tight only
Tighten each nut fully in clockwise order around the wheel
Explanation:
A star pattern ensures the wheel seats evenly on the hub and prevents warping or uneven clamping.
13. What is the purpose of small adhesive or clip-on weights fitted to wheels?
To reduce the tyre's rolling resistance by reshaping the rim
To increase the tyre's grip on wet roads
To balance the wheel and tyre assembly so it rotates without causing vibration
To change the tyre's speed rating
Explanation:
Wheel weights correct uneven mass distribution so the wheel is dynamically balanced and vibration-free at speed.
14. What is a run-flat tyre designed to do?
Change colour when air pressure is low
Automatically inflate itself to correct pressure when punctured
Allow limited driving after a puncture so the vehicle can be driven to safety or a repair shop
Remove stones from the tread while driving
Explanation:
Run-flat tyres have reinforced sidewalls or support systems that let the car continue at reduced speed for a limited distance after loss of pressure.
15. What does the tyre load index number indicate?
The maximum load capacity the tyre can carry at the specified pressure
The tyre's age in months
The tyre's fuel efficiency grade
The recommended wheel alignment setting
Explanation:
The load index is a coded number that corresponds to a maximum load rating for the tyre; you must choose tyres with the correct index for the vehicle.
16. How does a lower tyre aspect ratio (e.g. 50 instead of 70) affect ride and handling?
Always increases fuel consumption dramatically
Prevents any risk of punctures
Gives firmer ride and usually sharper handling with less sidewall flex
Increases the tyre's tread depth automatically
Explanation:
Lower aspect ratio means a shorter sidewall which reduces flex for better handling but gives a firmer, less comfortable ride.
17. Why should wheel nuts be re-checked (re-torqued) after a short distance of driving following a wheel change?
Because the wheel may settle on the hub and nuts can loosen slightly, so re-torquing ensures safety
Because the wheel will shrink and need retightening
Because tyre air pressure will automatically double during the first few kilometres
Because wheel nuts are designed to loosen by law
Explanation:
Re-torquing after a short drive ensures the nuts remain at the correct torque after the wheel seats and vibration has occurred.
18. How can worn suspension parts affect tyre condition?
They can cause uneven tyre wear and poor handling
They increase the tyre's legal speed rating
They make the tyres change colour
They convert tubeless tyres into tube tyres
Explanation:
Worn shocks, struts or bushings change wheel alignment under load, leading to irregular tyre wear and reduced stability.
19. What is an advantage of carrying a full-size spare wheel compared to a space-saver (donut) spare?
A full-size spare will clean the brake discs
A full-size spare increases engine horsepower
A full-size spare provides the same driving performance and can be used for longer distances
A full-size spare automatically balances itself
Explanation:
Full-size spares match the vehicle's tyres and allow normal driving, while space-savers are temporary and have speed/distance limits.
20. What is the bead of a tyre?
The deepest part of the tread pattern
The edge of the tyre that seats against and seals to the wheel rim
A tool used to remove a tyre from the rim
A type of wheel bearing
Explanation:
The bead contains reinforced wire and rubber that ensures the tyre fits tightly to the rim and maintains an air seal.
21. What is the primary purpose of a hubcap or wheel cover?
To change the tyre's load index
To improve appearance and protect the wheel nuts and hub from dirt
To reduce engine oil consumption
To automatically adjust tyre pressure
Explanation:
Hubcaps mainly serve cosmetic purposes and help keep dirt and moisture away from wheel nuts and the hub area.
22. What is the purpose of siping (small slits) in a tyre tread?
To prevent the tyre from ever needing balancing
To make the tyre weigh less
To improve traction on wet or slippery surfaces by creating additional biting edges
To increase the tyre's inflation pressure permanently
Explanation:
Sipes provide extra edges that help channel water away and improve grip on wet or icy roads.
23. When should you replace a tyre immediately?
When the wheel cover is missing
When the tyre colour fades from black to grey
When it gets slightly dirty
When tread is below the legal minimum or there is severe sidewall damage or bulging
Explanation:
Low tread, cuts, bulges or exposed cords are signs of dangerous tyre condition requiring immediate replacement.
24. What does a tyre pressure monitoring system (TPMS) do in a modern car?
Alerts the driver when tyre pressure is too low or varies between wheels
Changes wheel alignment while driving
Automatically repairs punctures without tools
Measures fuel level in the tank
Explanation:
TPMS uses sensors to warn the driver of low tyre pressure, helping to maintain safety and fuel efficiency.
25. Why must the rim size match the tyre size specified for the vehicle?
Because an incorrect rim can prevent the tyre from seating correctly and can be unsafe
Because wrong rims automatically fix brake faults
Because a mismatched rim makes the tyre produce more tread
Because mismatched rims will increase engine oil
Explanation:
Tyres and rims are designed to fit together; wrong rim diameter or width can cause sealing failure, poor handling or tyre damage.