## 3 Experimental Results and Discussions
Figure 5: The degree of wear of the brake pads: -view of the right-left pads (**a**); enlarged view—right-plate (**b**). Figure 6: Comparison between the new and used brake pads: side view (**a**); top view (**b**). The brake dynamometer rollers set the vehicle's wheels in motion at a speed of \(5\,\mathrm{km/h}\). At the same time, the test stand software collects data regarding the braking system parameters (Figure 8), obtained by successive actuation of the braking system by the operator, so that at the end, this generates a report with the exact results. The results according to the vehicle mass and the number of driven kilometers are presented in Table 3 and graphically in Figure 9.  
Figure 8: Visualization of the measured system: parameters of the braking system on analog display. Figure 7: Brake-pad wear measurement: (**a**) from the front axle; (**b**) from the rear axle. By using relation (1), service brake efficiency, \(\eta_{s}\), and parking brake efficiency, \(\eta_{p}\), can be calculated thus  
\[\eta_{s},\%_{s}\ =\ \frac{\textit{Total braking force on the axis}\ \ (6.81+3.89\ =\ 10.70\ \text{kN}\ \approx 1070\ \text{kg})}{\textit{Vehicle mass}\ (1566\ \text{kg})}\times 100\ \approx 69\ \%,\]  
respectively,  
\[\eta_{p},\%_{s}\ =\ \frac{\textit{Total braking force on the axis}\ \ (2.05+1.55\ =\ 3.60\ \text{kN}\ \approx 360\ \text{kg})}{\textit{Vehicle mass}\ (1566\ \text{kg})}\times 100\ \approx 23\ \%.\]  
As mentioned, the braking force values of the parking brake were measured on the dynamometer stand and were as follows: 3.60 (2.05 + 1.55) kN for /1566 kg/115,477 km: 2.92 (1.62 + 1.30) kN for 1462 kg/134,141 km; 2.67 (1.48 + 1.19) kN for 1480 kg/134,141 km; 2.89 (1.68 + 1.21) kN for 1526 kg/134,141 km. From the analysis of results in Table 4 and Figure 10, a significant reduction in the efficiency of the braking system can be observed, namely by 16% after 18,664 km driven. This is explained by the facts that the vehicle was used in urban traffic conditions (intense), which have led to more accelerated wear of the brake pads and discs. In Table 5 and Figure 11, the evolution of the efficiency of the braking system is presented, as well as the measured braking force, depending on the variation in the vehicle mass (1484, 1526, and 1566 kg, with the share of 946, 948, and 975 kg on the front axle (axis 1), and of 534, 536, and 551 kg on the rear axle (axis 2), respectively) and the number of driven kilometers (115,477, 134,141, and 139,334, when the traveled distance increased by 5193 km, from 134,141 to 139,334 km). The condition of choosing these vehicle masses was to observe the efficiency of the braking system when the mass was approximately the same (1480 and 1484 kg) and the number of kilometers traveled increased significantly (from 115,477 to 139,334 km), on the one hand, and on the other hand, when both the mass (from 1480 to 1526 kg) and the number of kilometers traveled increased. To determine the braking time and distance, depending on the auto-vehicle speed, a successive test series were carried out in the field. At the time of the tests, the vehicle had a mass of 1526 kg. Under normal vehicle load conditions (mass of 1526 kg), an efficiency of the braking system of only 59% was observed. Considering the fact that the minimum acceptable efficiency of the braking system is 43.5% (see Table 6), the results are worrying, suggesting the need to replace the braking system at a much shorter interval than the recommended one. After the change of the worn brake disc and pads, it was found that the efficiency of the braking system increased to 72%.