Abstract: A substantially "U" shaped break-away-bar assembly is constructed to a size and configuration to fit about a portion of an air-inflated vehicle tire. A key actuated lock latching assembly is carried by the break-away-bar assembly and includes an internally threaded connection member utilized to selectively connect the latching assembly to the external threads normally provided on a valve-stem of a tire rim for an air inflated vehicle tire. Operation of the key actuated lock to its locked condition prevents disconnection of the latching assembly from the valve stem. When the break-away-bar assembly is positioned about the vehicle tire and the latching assembly threadably connected to the valve stem rotation of the vehicle tire so that the bar assembly moves beneath the tire, rips the valve stem out of its seat and permits relatively rapid escape of the air from the tire. Slip joints provided for the break-away-bar assembly permit selective adjustment thereof to accommodate different size tires.