Abstract: If the height of a train car is reduced by the regrinding of the tread of each wheel and then reincreased to the original level by simply increasing the height of air springs, the compression stroke of the air springs changes. An arrangement is proposed to maintain a constant compression stroke after height adjustment. A stopper has movement restricting portions arranged circumferentially at predetermined intervals for restricting the downward movement of the outer cylinder. The stopper is rotatably mounted on the inner member. The outer cylinder has surfaces to be supported, and second surfaces to be supported provided circumferentially alternating with the first surfaces at a level lower than the first surfaces such that when the stopper is turned, the restricting protrusions move from the position where they support the first surfaces to the position where they support the second surfaces. The stopper has a lever so that it can be turned by operating the lever from outside.