The aim of this thesis work has been to develop a method for tribological evaluation in a test rig between piston and cylinder bore in a Hägglunds COMPACT hydraulic motor at high loads and low speed. The reasons for performing tests in a test rig are the lower costs and shorter testing time as compared to full-scale tests. Tests have been carried out with different combinations of functional surfaces. The test rig that has been used is a Cameron Plint TE 77 high frequency friction machine. Test specimens have been cut out from actual motor parts. Wear has been quantified with a Wyko NT1100 3-D topometer. Pistons that have been tested are: Standard piston, super polished piston, Balinit C coated piston and polished Balinit C coated piston. Cylinder bores that have been tested are: Standard cylinder bore, laser remelted cylinder bore and polished cylinder bore. A combination of a polished cylinder bore and a polished Balinit C coated piston has given the lowest total wear. The total wear for this combination is approximately 20% of the total wear on a combination of standard surfaces. All combinations with coated pistons have given lower total wear than uncoated. All combinations with polished cylinder bores have given good results. All combinations with Balinit C pistons give lower friction, polished Balinit C the lowest, approximately 85% of the friction for a combination of standard surfaces. The friction for all other combinations is equal. There is no direct connection between wear and the change in surface parameters before and after test. It is also hard to find a surface parameter that can predict the wear rate in this test. It should be kept in mind that the results of the tests only are valid under low speed and high load conditions. If the conditions are changed, another combination of surfaces can be more suitable. Surface parameters will probably have bigger influence at higher speed, when a thicker oil film can be built up.