## 2 Measurement Methods and Equipment: Laboratory Drum  
The thermal evolution of the tire tread has an important effect on the rolling resistance, wear, grip and overall tire performance. All the experimental tests were realized on a radial main landing gear aircraft tire. The main goal of these experiments is to study the thermal evolution of the aircraft tire at high velocity up to 190 km/h. The temperature evolution of the rubber tread and inside grooves was acquired by means of an infrared high speed camera installed on the test-rig (Figure 2a); the infrared camera was oriented to have an optimal view of the contact area through a golden reflecting mirror (Figure 2b or Figure 2d). Specific sensors have been used for force and moment measurements. Figure 1: Typical drum testing machine/external surface test [12]. A steel drum of 3.0 m in diameter is used in this study; special precautions for the set-up procedure were required. The tire must be already rotated with the prescribed skidding angle before coming into contact with the drum surface. The initial contact between the tire and the drum surface must be established before the drum starts rotating by applying a slight normal loading. In order to prevent wear and a significant heating of the tire, a special acceleration step is necessary before loading the tire to the nominal load, Figure 3 represents the test protocol. Set-up procedure steps:  
* Acceleration step, from s\({}_{1}\) = 0 km/h up to s\({}_{2}\) km/h during t\({}_{1}\) seconds at preliminary constant loading l\({}_{1}\) = l\({}_{2}\) kN and a given skidding angle \(\beta\). * Loading step, vertical loading increases up to l\({}_{3}\) kN during t\({}_{2}\) seconds, at constant velocity s\({}_{3}\) = s\({}_{2}\) km/h. * Rolling step at constant velocity s\({}_{3}\) = s\({}_{2}\) km/h, at constant loading l\({}_{3}\) kN during t\({}_{3}\) seconds. * Unloading step from l\({}_{4}\) = l\({}_{3}\) kN down to l\({}_{5}\) = 0 kN within t\({}_{4}\) seconds. As it was noted, the skidding angle value is fixed during all the experimental steps. In order to protect the camera from impacting rubber debris, a reflection mirror was installed and the camera pointed toward it. Since different skidding angles had to be studied, the camera was readjusted for each test in order to have an optimal view of the contact zone (Figure 2d). With regard to the temperature acquisition, a leaving-contact zone was defined just at the tire-drum interface, as it could be observed on the Figure 2c (red dot indicates the drum-tire contact zone). This zone concerns the temperature distribution just at the end of the tire-drum contact. Due to software limitations, the temperature was obtained using two times 30 data points along the aforementioned interface line. One data shot corresponds to one frame. The total number of frames depends on the acquisition frequency. By post processing techniques and further data handling, all measured values in pixels, points positions and acquisition frames were converted to degrees, mm and seconds. Figure 4b shows a typical temperature distribution at the end of the contact zone for several frames. Figure 2: (**a**) Experimental set-up (**b**) tire position, view camera/before loading, (**c**) tire position, view camera/after loading, (**d**) mirror and infrared camera positions. Figure 4a shows the tire/drum configuration. The origin of the coordinate system was chosen to be in the middle of the tire. Thus, the left side corresponds to positive Y values and the right side to negative Y values (Figure 4c). 30 points for each side of the tire tread were used to record the thermal evolution. Figure 4b shows the temperature distribution as a function of the point position within the  
Figure 4: Experimental set-up: (**a**) tire/drum configuration (**b**) temperature distribution in the contact zone, (**c**) the thermal evolution of contact zone. Figure 3: The test protocol. (**a**) loading steps, (**b**) velocity strategy, (**c**) skidding angle. tire tread profile.