As part of the periodic technical vehicle inspection, adherence to the minimum statutory performance requirements specified in 2014/45/EU must be proved during brake testing. To this end, roller brake testers are used in most cases. Due to the increased minimum performance requirements (e.g., an increase from 50% to 58% of the GVWR-related minimum deceleration for vehicle class M1), a conventional verification without loading or loading simulation of the vehicle is hardly possible in many vehicles with a high load/no load ratio. Furthermore, no information at all can be obtained on how the braking force is distributed across individual axles.
The German PTI brakes directive stipulates that the reference braking force method described in ECE-R13 for vehicles with air brakes is also mandatory for vehicles with hydraulic brakes during PTI. As in the case of air brake systems, brake pressure serves as the reference value. However, it is not measured by externally attached pressure gauges, but is electronically retrieved from the vehicle's ESP system via the vehicle diagnostic interface. By implementing the pressure-based reference braking force method for vehicles with hydraulic brakes, it becomes possible to evaluate the braking forces determined with roller brake testers in relation to specific axles as a function of the brake cylinder pressure.
The application of this test method considerably improves the assessment of the brake system in the context of periodic technical vehicle inspections, since both the braking effect of the individual axles and the braking force distribution can be examined very effectively and efficiently. The relevant specifications are provided by the Central agency for PTI / FSD. The Central agency for PTI / FSD is a non-profit organization whose shareholders are all PTI institutions in Germany; inter alia, it is responsible for the provision of specifications for implementing the periodic technical vehicle inspection. This revised test methodology is presented in detail in this technical paper, which discusses its physical principles and advantages as well as the legal framework of Germany and the EU.
Jürgen Bönninger, Marco Stiller, Lars Stastny - Central agency for PTI / FSD Fahrzeugsystemdaten GmbH