Running-in process of low metallic brake pads and cast iron discs are investigated using full scale inertia brake dynamometer designed for particle emission studies. The airborne particles are measured using ELPI+ and collected on filters. The pads and disc contact surfaces are studied using microscopy techniques. It is observed that the particle emissions from the new pads and discs are significantly higher compared with the used ones and indicates importance of proper running-in of the pads and disc for wear particle emission tests. The results also indicate that pads and disc pairs which are able to stabilize friction behavior faster will produce less particle emissions which could influence the strategies of brake material formulations or steps during their production. •Difference in particle emissions for new and used pads.•Running in of pads and discs is necessary to reach stable wear particle emissions.•Running-in of brake discs takes longer than running-in of pads.•Proper running-in has to be taken in consideration for tests focused on wear particle emissions.•Brake pads which develop stabile friction layer faster produce less wear particles.