On a long downhill road, a driver kept pressing only the foot brake and the brakes overheated. The heat created bubbles in the brake fluid, so the pedal sinks and the car barely slows down. What is this phenomenon called?
💡 Hint
Tell vehicle phenomena apart by whether the cause is heat, water or tire pressure, and whether the problem is in the brake fluid, the brake pads or the tires. It is easy to confuse this with fading, which is also caused by heat.
Answer: ③
Explanation
When the brakes are used continuously for a long time, friction heat boils the brake fluid and creates bubbles in the lines; pedal force is absorbed by the bubbles and braking weakens. This is vapor lock. Aquaplaning is when tires ride on a film of water on a wet road, and the standing wave phenomenon is when an underinflated tire deforms in waves at high speed. On long downhills, prevent it by also using the engine brake in a low gear.
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