A wheel (Aluminum, CTE = 20 µm/m°C) of internal diameter 0.5 m has a speed sensor which is placed inside of the wheel, and is sensitive to the size of the wheel. It stops working if the distance between the sensor and the wheel changes by more than 0.5 mm from its calibration, which happens at 25 °C. Under racing conditions the wheels get to 55 °C, and in snowy conditions the wheels get to -40 °C.