A gantry apparatus for a proton treatment system, including a proton beam nozzle to emit a proton beam to a targeted region of a patient, a gantry wheel to support the proton beam nozzle to direct the proton beam to an isocenter of the gantry wheel corresponding to a center of the targeted region, a plurality of adjustable bearings incrementally spaced apart along an outer diametrical surface of the gantry wheel, and a bearing surface to support a portion of the adjustable bearings such that when the wheel is rotated from a first angular position to a second angular position, at least a portion of the bearings contact the bearing surface to raise or lower the gantry wheel to realign the proton beam to the center of the targeted region.
