Arizona Air Brakes CDL Practice Test

What is the proper way to check the free play of manual slack adjusters on S-Cam brakes?

1. A. Park on level ground, chock the wheels, and release the parking brakes.

2. B. Stop on level ground and apply the parking brakes.

3. C. Park on level ground and drain off air pressure before adjusting.

4. D. Park on a slight grade, release the parking brake, apply the service brakes, and check for vehicle movement.

The correct answer is: A. Park on level ground, chock the wheels, and release the parking brakes.

The proper way to check the free play of manual slack adjusters on S-Cam brakes involves ensuring that the vehicle is safely positioned and that the parking brakes are released to accurately gauge the slack adjuster's function. When you park on level ground and chock the wheels, it prevents any unintended movement of the vehicle while you're checking the slack adjusters. Releasing the parking brakes allows you to properly test the free play without any interference, ensuring that you can accurately measure the adjustment and performance of the brakes. Other methods may not provide an accurate assessment of the slack adjusters. For instance, applying the parking brakes would prevent proper movement necessary for the check. Draining air pressure before adjusting, while important during actual adjustments, is not relevant to checking free play. Lastly, checking on a slight grade could introduce movement that would affect the accuracy of your assessment.