What determines the pushrod stroke in an air brake system?
- The pressure of the compressed air that enters the brake chamber ✓
- The type of vehicle
- The weight of the vehicle
- The strength of the return spring
Answer: A. The pressure of the compressed air that enters the brake chamber
The pushrod stroke is determined by the pressure of the compressed air that enters the brake chamber.
Why this is the answer
The handbook says pushrod stroke depends on how much compressed air pressure enters the brake chamber. It gives an example: when application pressure rises from 69 kPa to 552 kPa, the stroke increases noticeably. Another passage says pushrod stroke is produced by compressed air entering the chamber. That supports air pressure as the factor that sets how far the pushrod moves.
Why the other answers are wrong
- B. The type of vehicle — The type of vehicle can affect how fast brakes wear and what adjustment limit applies, but the passages do not say it determines the pushrod stroke itself.
- C. The weight of the vehicle — The passages do not mention vehicle weight as something that sets pushrod stroke.
- D. The strength of the return spring — The return spring brings the pushrod back when air pressure is released; it does not create the pushrod stroke.
Remember it
Think: air pushes the rod out, and the spring pulls it back.