Abstract: A pneumatically operated adjustable trailer chassis includes a frame which slides with respect to the trailer portion of a tractor trailer rig. The frame carries wheels with the sliding support portion so that the wheel position of the wheels can be adjusted for and after with respect to the frame portion of the tractor trailer rig. A locking pin is used to rigidly support and fix the position of the sliding support with respect to the frame and thus the position of the wheel with respect to the trailer. A pneumatic operator engages and disengages the locking pin from a remote location. An interface connects the pneumatic operator with the air supply line that supplies air to the brakes of the trailer wheels so that compressed air supplied aft to operate the brakes also operates the locking pin.