A centrifugal compressor , comprising: a gear box comprising a retaining bore; and a rotor assembly , comprising: a rotor ; a first bearing disposed about the rotor and configured to reduce friction acting on the rotor , wherein the first bearing is disposed within the retaining bore of the gear box ; and a first annular bearing retainer ring disposed about the rotor and within the retaining bore of the gear box , wherein the first annular bearing retainer ring comprises: a first axial surface , wherein the first axial surface is planar; and a second axial surface opposite the first axial surface , wherein the second axial surface is non-planar, the second axial surface including an inner radial surface and an outer radial surface , wherein a first thickness between the inner radial surface and the first axial surface is less than a second thickness between the outer radial surface and the first axial surface , characterized in that the first annular bearing retainer ring is structured to be selectively positioned in a first orientation or a second orientation relative to the first bearing to adjust the first bearing between a first axial position and a second axial position in the retaining bore, the first bearing being at the first axial position and abutting the inner radial surface , and not the outer radial surface when the first annular bearing retainer ring is in the first orientation, the first bearing being at the second axial position and abutting the first axial surface when the first annular bearing retainer ring is in the second orientation, the first axial position being different than the second axial position. a gear box comprising a retaining bore; and a rotor assembly , comprising: a rotor ; a first bearing disposed about the rotor and configured to reduce friction acting on the rotor , wherein the first bearing is disposed within the retaining bore of the gear box ; and a first annular bearing retainer ring disposed about the rotor and within the retaining bore of the gear box , wherein the first annular bearing retainer ring comprises: a first axial surface , wherein the first axial surface is planar; and a second axial surface opposite the first axial surface , wherein the second axial surface is non-planar, the second axial surface including an inner radial surface and an outer radial surface , wherein a first thickness between the inner radial surface and the first axial surface is less than a second thickness between the outer radial surface and the first axial surface , a rotor ; a first bearing disposed about the rotor and configured to reduce friction acting on the rotor , wherein the first bearing is disposed within the retaining bore of the gear box ; and a first annular bearing retainer ring disposed about the rotor and within the retaining bore of the gear box , wherein the first annular bearing retainer ring comprises: a first axial surface , wherein the first axial surface is planar; and a second axial surface opposite the first axial surface , wherein the second axial surface is non-planar, the second axial surface including an inner radial surface and an outer radial surface , wherein a first thickness between the inner radial surface and the first axial surface is less than a second thickness between the outer radial surface and the first axial surface , a first axial surface , wherein the first axial surface is planar; and a second axial surface opposite the first axial surface , wherein the second axial surface is non-planar, the second axial surface including an inner radial surface and an outer radial surface , wherein a first thickness between the inner radial surface and the first axial surface is less than a second thickness between the outer radial surface and the first axial surface , <EOS>