A bearing monitoring system and an air cycle machine comprising: a housing; a compressor disposed within the housing; a turbine disposed within the housing; an axial shaft operatively coupled to the compressor and the turbine, the axial shaft disposed within the housing and between a first plurality of bearings (20, 24); a thrust runner extending from the axial shaft, the thrust runner disposed within the housing and between a second plurality of bearings; and at least one sensor (36, 40) mounted to the housing and oriented to monitor deflection of the thrust runner, wherein the at least one sensor comprises: an axial sensor positioned to target an outer diameter of the thrust runner to detect an axial deflection of the thrust runner; characterized in that the at least one sensor also comprises a first radial sensor positioned to target an end of the thrust runner to detect a radial deflection of the thrust runner; and in that the at least one sensor also comprises a second radial sensor positioned to target the end of the thrust runner to detect the radial deflection of the thrust runner, the first and second radial sensor targeting the end of the thrust runner at an angular displacement of 90 degrees from each other, and wherein the second plurality of bearings (20, 24) is thrust bearings comprising foil bearings, and wherein the second plurality of bearings (22, 24) extend to a first radial distance and the thrust runner extends to a second radial distance that is further from the axial shaft relative to the first radial distance to provide an axial target for the at least one sensor. a housing; a compressor disposed within the housing; a turbine disposed within the housing; an axial shaft operatively coupled to the compressor and the turbine, the axial shaft disposed within the housing and between a first plurality of bearings (20, 24); a thrust runner extending from the axial shaft, the thrust runner disposed within the housing and between a second plurality of bearings; and at least one sensor (36, 40) mounted to the housing and oriented to monitor deflection of the thrust runner, wherein the at least one sensor comprises: an axial sensor positioned to target an outer diameter of the thrust runner to detect an axial deflection of the thrust runner; characterized in that the at least one sensor also comprises a first radial sensor positioned to target an end of the thrust runner to detect a radial deflection of the thrust runner; and in that the at least one sensor also comprises a second radial sensor positioned to target the end of the thrust runner to detect the radial deflection of the thrust runner, the first and second radial sensor targeting the end of the thrust runner at an angular displacement of 90 degrees from each other, and wherein the second plurality of bearings (20, 24) is thrust bearings comprising foil bearings, and wherein the second plurality of bearings (22, 24) extend to a first radial distance and the thrust runner extends to a second radial distance that is further from the axial shaft relative to the first radial distance to provide an axial target for the at least one sensor. an axial sensor positioned to target an outer diameter of the thrust runner to detect an axial deflection of the thrust runner; characterized in that the at least one sensor also comprises a first radial sensor positioned to target an end of the thrust runner to detect a radial deflection of the thrust runner; and in that the at least one sensor also comprises a second radial sensor positioned to target the end of the thrust runner to detect the radial deflection of the thrust runner, the first and second radial sensor targeting the end of the thrust runner at an angular displacement of 90 degrees from each other, and wherein the second plurality of bearings (20, 24) is thrust bearings comprising foil bearings, and wherein the second plurality of bearings (22, 24) extend to a first radial distance and the thrust runner extends to a second radial distance that is further from the axial shaft relative to the first radial distance to provide an axial target for the at least one sensor.