Abstract: A first visual indicium (44) and a second visual indicium (50) are provided on a push rod (10) in an air operated diaphragm spring brake. The push rod (10) is mounted for reciprocal movement between an operative position and an inoperative position through an opening (26) in a service brake housing (16). The first indicium (44) comprises a discontinuity (45) in the surface of the push rod (10) having a leading edge (46) and grooves (48). The first indicium is positioned on the push rod such that the leading edge (46) will be exterior to the service chamber (12) only when the push rod is in the operative position and the brakes are substantially out of adjustment. The second visual indicium (50) comprises a second discontinuity formed of at least a leading edge (52) and a trailing edge (54). The second visual indicium (50) is positioned on the push rod whereby the trailing edge (54) will normally be exterior of the service chamber 12 adjacent the opening (26) when the push rod is in the inoperative position.