Vehicle knowledge
What the exam tests
Vehicle knowledge checks your understanding of C1 lorry systems and legal weights: chassis, brakes, tyres, coupling, lights, mirrors and daily checks.
Core rules
- C1 lorries have a permissible total weight of 7,500 kg. Payload is total weight minus kerb weight, but axle limits may reduce it further.
- Braking systems may be hydraulic or air; know warning symbols and the daily brake test. ABS prevents wheel lock but does not shorten every stopping distance.
- Tyres must carry the load, have correct pressure and meet tread depth. For vehicles over 3.5 t, winter tyres need at least 5 mm tread in winter conditions.
- Check lights, mirrors, coupling, load security and fluids before driving. The tachograph must be functioning and correctly used.
Worked example
A C1 lorry has a kerb weight of 3,300 kg and a permissible total weight of 7,500 kg. The front axle is rated 3,500 kg and the rear axle 5,000 kg. What is the theoretical payload? 7,500 − 3,300 = 4,200 kg. But if the driver and load are placed so the rear axle reaches 5,000 kg before the total reaches 7,500 kg, the real payload is lower. You must weigh or calculate axle loads, not just subtract kerb weight.
Traps
Do not confuse gross vehicle weight with gross train weight. Do not assume ABS removes the need for safe following distance. Do not fit car tyres with too low a load index. Do not ignore a brake warning light.