This paper presents results of pressure oscillation investigation in hydraulic hitch-system of a tractor Claas Ares ATX 557 during the motion during artificial roughness road test. During experiments oscillation at different driving speed, tyre pressure and hitch-system oscillation damping (turned on/off) were investigated. Tractor hydraulic hitch-system was equipped with a pressure sensor Wika Transmitter ECO-1 and data processing software PicoLog. Results of experiments present maximum pressure peak of 210 bar in the tractor hydraulic system when hydraulic hitch-system oscillation damping system at driving speed 8 km·hE-1 is not used and system pressure peak reduces to value of 180 bar if the hydraulic hitch-system oscillation damping is used.

In order to perceive the pressure oscillation in the hydraulic hitch-system of the tractor and oscillation of the whole tractor aggregate at different loads on the hitch-system, a physical model is used. Changing the position of weight on physical implement boom, different moments of inertia were obtained and the appropriate load on the hydraulic hitch-system hydro cylinder. Results of driving experiments on the artificial roughness road present the maximum pressure peak of 220 bar in the tractor hydraulic system when weight was placed on further position, and the driving speed was 8 km hE-1 and tyre pressure was 1.2 bar. At the driving speed of 11.2 km hE-1 and with the same tyre pressure, the hydraulic system pressures reached up to 212 bar. On the weight on the middle position of boom, pressure in the hydraulic hitch-system reached 172 bar at the driving speed of 7.8 km hE-1 and tyre pressure of 1.2 bar, but at the driving speed of 11.2 km hE-1 and at the same tyre pressure, the hydraulic system pressures reached 165 bar. If the weight was placed on nearest position, pressure in the hydraulic hitch-system reached only 85 bar at the driving speed of 7.8 km hE-1 and tyre pressure - 1.2 bar, but at the driving speed of 11.2 km hE-1 and at the same tyre pressure, it was 98 bar. The investigation of the physical tractor-implement model allows the determination of the conformity of the physical model with real harrow implement.