In this paper, the characteristics of disk-type hydrostatic thrust bearings supporting concentric loads; simulating the major bearing/seal parts of axial piston pumps and motors were investigated. An experimental setup was designed to determine the performance of slippers, which are capable of increasing the efficiency of axial piston pumps and motors, for different conditions. The working parameters and the slipper geometry causing the minimum frictional power loss and leakage oil loss were determined. Since slippers affect the performance of the system considerably, the effects of surface roughnesses on lubrication were studied in slippers with varying hydrostatic bearing areas and surface roughness. The results of the study suggest that the frictional power loss and leakage oil loss were caused by the surface roughness, the relative velocity, the size of the hydrostatic bearing area, supply pressure and capillary tube diameter.