In the article the ways of defining tyre rolling resistance are presented. The advantages of the laboratory tests of tyre/road rolling resistance and the advantages and the disadvantages of on the road tyre/road rolling resistance tests are described. The description of the special trailer used for tyre/road rolling resistance measurements designed and constructed in Faculty of Mechanical Engineering at Gdansk University of Technology is presented also. The trailer during it’s modernisation was equipped with special test systems which compensate the impact of disturbance factors such as: aerodynamic drag and inertia force acting on the tested tyre, slope of the road, tilt of the trailer and vibrations of the measuring arm. This article contains the description of only one compensation system applied in the measuring trailer which eliminates the aerodynamic drag. The conclusions which came from the measurements performed using this compensation test system are included.