Air braking systems tend to react slower than hydraulic braking systems because
- the drum brakes are designed differently.
- of the compression and movement of the air. ✓
- back pressure on the foot valve is greater.
- it takes a lot of force to release the spring brakes.
Answer: B. of the compression and movement of the air.
Air braking systems react slower because of the compression and movement of the air.
Why this is the answer
The handbook says hydraulic brakes use brake fluid, which cannot be compressed, so force reaches each wheel immediately when you press the pedal. Air brakes use compressed air stored in tanks to produce force. Because the air has to compress and move through the system, the response is not instant. The same handbook notes a split-second delay is present in all air brake systems. That contrast between incompressible fluid and compressed air is what makes the air system react more slowly.
Why the other answers are wrong
- A. the drum brakes are designed differently. — The passages say air-brake vehicles may use drum or disc components, so drum design is not given as the reason for a slower reaction.
- C. back pressure on the foot valve is greater. — Back pressure on the foot valve is not mentioned in the passages, and nothing there links it to slower air-brake response.
- D. it takes a lot of force to release the spring brakes. — The passages do not say that releasing spring brakes requires a lot of force or that this affects how quickly the brakes apply.
Remember it
Think fluid is instant, air has to travel: hydraulic pressure is immediate, air pressure lags.