Grade 10 power mechanics – Road Wheels Quiz
1. What is the primary function of a vehicle's road wheel?
Road wheels carry the vehicle's weight and provide a rolling surface so the vehicle can move along the road.
2. Which part of the wheel holds and seals the tyre to the rim on modern cars?
The tyre bead is the reinforced edge of the tyre that sits against the rim flange and creates an airtight seal for tubeless tyres.
3. What does the tyre marking '195/65 R15' tell you?
Tyre codes show width in millimetres, aspect ratio as a percentage of width, and rim diameter in inches (R for radial).
4. Which tyre type is most common on modern Kenyan passenger cars?
Radial tyres are widely used for passenger cars because they give better grip, fuel economy and ride comfort compared with bias-ply tyres.
5. What is the main danger of driving with under-inflated tyres?
Under-inflation increases the tyre's contact area and flexing, causing higher wear, heating and possible tyre failure.
6. Why is wheel balancing important?
Balancing ensures mass is evenly distributed so wheels do not vibrate, improving comfort and tyre life.
7. What does wheel alignment adjust?
Alignment sets the wheel angles (camber, caster, toe) so tyres contact the road correctly and wear evenly.
8. Which of these indicates positive camber?
Positive camber is when the top of the wheel leans away from the vehicle centreline.
9. What does 'toe-in' mean in wheel alignment terms?
Toe-in refers to wheels pointing slightly toward each other at the front, affecting steering stability and tyre wear.
10. How often should tyres be rotated to extend tyre life on a typical family car?
Regular tyre rotation evens wear among tyres; manufacturers commonly recommend rotation every 8,000–12,000 km.
11. What is the correct first step before removing a wheel from a parked vehicle?
You must secure the vehicle by setting the parking brake and placing wheel chocks to prevent rolling before jacking and removing a wheel.
12. What tool is normally used to loosen wheel nuts before lifting the vehicle?
A wheel or lug wrench provides the leverage to loosen tight wheel nuts safely before raising the vehicle on a jack.
13. Which wheel component allows the wheel to rotate smoothly around the axle?
Wheel bearings are rolling element assemblies that support the wheel and allow smooth rotation with minimal friction.
14. What is the main advantage of tubeless tyres over tube-type tyres?
Tubeless tyres hold air at the bead and often seal small punctures, reducing sudden blowouts and simplifying repairs compared with tube tyres.
15. Why should wheel nuts be tightened in a star (criss-cross) pattern when fitting a wheel?
Tightening in a criss-cross pattern draws the wheel onto the hub evenly, preventing misalignment or damage to the wheel or brake disc.
16. What tyre tread pattern is best for wet roads to reduce risk of aquaplaning?
Grooves and sipes help move water away from under the tyre so the rubber keeps contact with the road, reducing aquaplaning.
17. How can worn wheel bearings commonly be identified while driving?
Worn bearings often make a rumbling, humming or grinding noise that varies with road speed and can indicate bearing failure.
18. What should you do immediately if you get a tyre puncture on a Kenyan road and cannot change the wheel safely?
Reducing speed, moving to a safe place and warning other road users keeps you safe until you can repair or change the tyre.
19. What does the speed rating letter on a tyre indicate?
Tyre speed ratings are letters that show the maximum speed a tyre is certified to carry a specified load safely.
20. Why must replacement wheels match the vehicle's bolt pattern and offset?
Bolt pattern and offset affect how the wheel mounts and its position; incorrect fit can cause rubbing, steering issues or unsafe load on bearings.
21. What is the recommended action for tyres that have tread depth below the legal or safe limit?
Tyres below the safe tread depth reduce grip, especially on wet roads, and should be replaced to maintain safety.
22. Which valve type is most common on car wheels for inflating and checking tyre pressure?
Schrader valves are the common, sturdy valve types found on most car tyres and accept standard air pumps and gauges.
23. What causes uneven tyre wear on the inner or outer edge of a tyre?
Misaligned camber or toe angles make the tyre contact uneven, leading to excessive wear on one edge.
24. When repairing a small puncture in a tubeless tyre, what is the common safe repair method at a workshop?
A proper repair combines an internal patch with an external plug and must be done correctly to restore tyre safety; roadside quick fixes are unsafe.
25. What effect does over-inflation of a tyre have on vehicle handling and tyre wear?
Over-inflation makes the tyre bulge at the centre, reducing grip, making the ride firmer and causing the centre of the tread to wear faster.