Truck Air Brake Warning: Manually Adjusting Automatic Slack Adjusters is Dangerous,
Can Lead to Deadly Consequences

Safety officials are warning hundreds of thousands of heavy truck operators, drivers,
mechanics, and federal and state commercial vehicle inspectors about the dangers of manually
adjusting automatic slack adjusters on vehicles equipped with air brakes.

National Transportation Safety Board (NTSB) Acting Chairman Mark V. Rosenker
bluntly warned: “Manually adjusting automatic slack adjusters is dangerous. It should not be
done, except during installation or in an emergency...
http://www.ntsb.gov/Events/journalis..._air_brake.txt

Very interesting article.

Some years ago I took a class so we were qualified to "Inspect and Adjust Brakes" but don't recall how to do the ASA's. [Just give me the little card to please the DOT man.]

Maybe some of the wrench turners would like to jump in about this.