Abstract: A slack adjuster adapted for use in railroad truck car braking mechanisms. The slack adjuster compensates for wear of the truck car brake shoes by automatically adjusting the length of travel of the brake cylinder piston rod as the shoes wear. The slack adjuster of this invention includes a linkage connected between the air cylinder piston rod and one end of the slack adjuster. The invention also includes a bolster mounted linkage stabilizer which interconnects the other end of the slack adjuster, the brake lever, and the piston rod to eliminate oscillation of the piston rod during operation.