Automatic Slack Adjusters for Heavy Vehicle Air Brake Systems

摘要

The report reviews the problem of truck air brake adjustment and specifically theuse of automatic slack adjusters (ASAs) to maintain proper brake adjustment on S-cam drum brakes. The report reviews the importance of proper brake adjustment for effective functioning of air brake systems. It describes methods of improving brake adjustment, with emphasis on ASAs. The report presents findings from a large field test of ASAs (with comparative data on manual slack adjusters; MSAs) used on heavy commercial vehicles. Project data indicated that the use of ASAs can be an efficient and effective means of maintaining brake adjustment. For the 36 ASA/fleet applications tested, the median percentage out-of-adjustment was 4.0 percent. The median number of out-of-adjustment observations per brake per 10,000 miles was 0.016. ASAs were, in general, significantly more effective than MSAs in similar applications.