What is an advantage of automatic slack adjusters?
- They require manual adjustment less frequently.
- They never need lubrication.
- They don't need to be checked by a qualified mechanic.
- They help maintain correct pushrod stroke. ✓
Answer: D. They help maintain correct pushrod stroke.
An advantage of automatic slack adjusters is that they help maintain correct pushrod stroke.
Why this is the answer
The handbook says automatic slack adjusters adjust themselves during normal brake applications and maintain brake stroke more reliably than manual adjusters. That reliable stroke is the advantage the question asks for: the pushrod stroke stays closer to its designed range without routine manual adjustment. The same passage still requires pre-trip checks and mechanic checks at recommended intervals, so the benefit is about holding correct stroke, not about skipping inspection or lubrication.
Why the other answers are wrong
- A. They require manual adjustment less frequently. — The handbook says a properly installed automatic slack adjuster shouldn't need manual adjustment, so saying it merely needs manual adjustment less often misses the stated advantage and understates how it works.
- B. They never need lubrication. — They do have lubrication requirements: the handbook points to service data books for lubrication requirements and recommends checks at chassis lubrication intervals.
- C. They don't need to be checked by a qualified mechanic. — They still must be checked during pre-trip inspections and by a mechanic at the recommended intervals, and stroke problems need a qualified brake service mechanic.
Remember it
Automatic adjusters keep brake stroke steadier during everyday stops, yet they still get inspected.