# Measurement and Modeling of a Cargo Bicycle Tire for Vehicle Dynamics Simulation
## 3 Results
### Observations during the Measurement  
During the test campaign, some noticeable findings were observed that contain:  
* Loose spokes of the adapter rim after steering measurements;
* High tire abrasion after steering measurements;
* Thin high-temperature line on the tire surface.  
When measuring \(F_{t,y}\) and \(T_{t,x}\) an increased occurrence of slightly loose spokes in the rim during the steering measurement series was observed. A possible explanation for this effect is based on the assumption that bicycle rims are developed for driving with higher camber angles; the high \(\alpha\) values with \(\gamma=0^{\circ}\) during the measurements can bend the rim.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & & & & & & & \\ \hline \multirow{6}{*}{**Output**} & \(F_{x}\) in N & \(F_{y}\) in N & \(F_{z}\) in N & \(T_{x}\) in Nm & \(T_{z}\) in Nm \\  & **[1203]** & **[1222]** & **[1200]** & **[305]** & **[--25]** \\ \hline \multirow{6}{*}{**Output**} & \(F_{x}\) in N & \(1165.781\) & \(22.869\) & \(-51.702\) & \(46.202\) & \(-10.975\) \\  & \(F_{y}\) in N & \(-32.988\) & \(1124.557\) & \(16.104\) & \(28.154\) & \(19.211\) \\ \cline{1-1}  & \(F_{z}\) in N & \(-38.956\) & \(-13.866\) & \(1235.548\) & \(-63.938\) & \(2.544\) \\ \cline{1-1}  & \(T_{x}\) in Nm & \(1.665\) & \(13.150\) & \(3.433\) & \(292.221\) & \(0.599\) \\ \cline{1-1}  & \(T_{z}\) in Nm & \(8.318\) & \(0.058\) & \(-4.131\) & \(-14.675\) & \(-25.366\) \\ \hline \hline \end{tabular}
\end{table}
Table 3: Crosstalk measurements.  
As a consequence, the spokes can be stressed by compressive forces even though they are optimized for tensile forces. The compressive force can relieve the spoke ripples and, consequently, the threads, which can then be loosened by oscillations in the system, as seen in Figure 6b for \(\alpha>6^{\circ}\). The spokes were checked after each series of measurements and tightened if necessary.  
Due to the high loads during the bicycle tire tests, a high level of tire abrasion was noticed. As the used tires do not have a mark for replacement, they were used until the tire tread was completely worn away. The complete removal of the tread by a series of measurements can be seen in Figure 8a. Figure 8b shows a tire that was overstressed as the internal mesh became visible. Measurements made with overstressed tires were not included in the evaluation, since the detached tread of the tire has a strong impact on the adhesion values.  
In order to evaluate the temperature behavior of the tires more accurately, the image shown in Figure 9 was obtained after a series of 18 steering measurements with the aid of a thermal imaging camera. As can be seen from the Figure, a thin line forms in the center of the tire, which reaches temperatures of approx. 52 \({}^{\circ}\)C. After a slim transition layer, the tire reaches a temperature of approx. 36 \({}^{\circ}\)C at the edge. Since the tire is driven without any camber angle, there is little to no friction at the edge areas of the tire. The local heat zones thus correspond to the overstressed tire tread shown in Figure 8b. Furthermore, the thermal imaging can ensure that a new tire survives a measurement series of 18 measurements without excessive temperatures. The tire image in Figure 8b is, therefore, the result of excessive testing.