Abstract: A brake slack adjuster and tire tester tool including a main support assembly having mounted thereon a connector hook assembly and, on an outer end, an arm connector and tire tester assembly. The tool support assembly has a main handle assembly having on one end a hand gripper assembly which is operable to be grasped by the user thereof. The connector hook assembly is provided with a main hook member secured to an outer portion of the main handle member and operable to grasp onto a portion of a rocker arm assembly of an air brake assembly on a truck/trailer assembly. The arm connector and tire tester assembly is provided with a tire tester section and an arm connector section. The tire tester section is operable for impacting an outer surface of a tire member to check the condition thereof.