For the ASR (Anti Spin Regulator) valve unit, which is to prevent the driving wheels from spinning, the material and the size of the valve inside the unit is improper, and therefore the valve may be deformed from deterioration over time caused by air pressure from behind and from high temperature. If the deformed valve blocks the exhaust port, it may happen that the pressure inside the brake pipe does not decrease and that the brake is activated all the time, which can cause the brake drums to overheat and in the worst case could result in a fire.