Slack Adjusters are the linkage between operating rod in the brake chamber and s-cam (drum brakes) or disk brakes in an air brake system. The main function of slack adjusters is to transfer motion from air brake actuating rod to ‘s-cam shaft’. They can be adjusted manually for brake lining wear. Chiefly, there are two types of slack adjusters:
1) Manual Slack Adjuster: These need to be adjusted using a wrench and you do this by getting underneath the truck. The Automatic adjuster automatically adjust themselves through the normal use of brake.
2) Automatic Slack Adjuster: In this, the distance between the wall of brake drum and brake lining is adjusted automatically. In a truck or trailer, we must not exchange them with the manual ones and vice-versa. The automatic adjusters are an improvement over the manual ones and eliminate the periodic adjustments. That said, even the automatic ones are not maintenance free.
Be sure to install the new slack adjuster in the same position as the old one or it will not function properly. Also, never use a reconditioned one. Vehicles in which brakes are used frequently, the slack adjuster should be checked more often. Greasing is always recommended in order to prolong the life of the adjuster. In fact, it is recommended to do greasing after every 25,000 kilometers and before the installation of slack adjuster. That is why we should warn the truck and trailer drivers to check the status of brake shoe, brake linings, springs and brake drums.