In the article the principle of measuring of tyre/road rolling resistance tyres in road conditions applied in a special measuring trailer is presented. This trailer was built in Faculty of Mechanical Engineering at Gdansk University of Technology. The construction of two special devices used in this trailer was discussed. These devices eliminate the influence of some chosen confounding measurements factors such as: the inertia force acting on the measuring arm with the wheel and the tested tyre and vibrations of the measuring arm. The operation of these devices was proven in practice. The conclusions arising from the use of these systems are described.