CDL Air Brakes TestInspecting Air Brake SystemsMedium
A driver observes that the slack adjusters on several wheels of a tandem axle trailer are beyond their adjustment limits. The brakes are out of adjustment. If the driver continues to operate the vehicle, what is the most significant immediate consequence?
- AIncreased fuel consumption due to brake drag.
- BReduced braking efficiency and increased stopping distance.
- CThe air compressor will have to work harder to maintain pressure.
- DPremature wear of the brake drums and linings on all wheels.
Show answer & explanationAnswer & explanation
Correct answer: B. Reduced braking efficiency and increased stopping distance.
Out-of-adjustment brakes, particularly those with slack adjusters beyond their limit, mean that the brake shoes will not apply with sufficient force or may not apply at all. This directly leads to reduced braking efficiency for those wheels and, consequently, a significantly increased stopping distance for the entire vehicle, posing a major safety hazard.
Why the other options are wrong
- A. Brake drag occurs with *over-adjusted* brakes or issues with return springs, not typically with brakes that are out of adjustment (too loose).
- C. Out-of-adjustment brakes don't necessarily cause more air loss; they just don't apply effectively. The compressor works harder with air leaks.
- D. While chronic misadjustment can lead to uneven wear, the *immediate* and most dangerous consequence is the loss of braking power, not just wear.
Slack Adjuster Adjustment Limits
Slack adjusters must be within a specific range of travel to ensure brakes engage properly. Excessive travel indicates worn components or improper adjustment.
- Manual slack adjusters should not move more than 1 inch at the pushrod.
- Automatic slack adjusters should adjust themselves, but must be checked.
- Out-of-adjustment brakes are a major cause of accidents.
Memory trick: Loose slack means brakes are bad; stopping distance makes you sad!