PURPOSE: To faciltate car adjustment and perform quick car height adjustment by screwing a mount base and a lock nut in a bearing housing that externally engages and holds the upper mounting position of a buffer.

CONSTITUTION: A mount base 4 and a lock nut 5 are externally engaged and screwed in a bearing housing 3 so as to freely swing. The mount base 4 is mounted on a car body frame using bolts. On the other hand, the bottom metal 7 at the bottom of a cylinder 1 is supported on a rear fork through a link. As a result, the mount base 4 mounted on the car body frame is elevated along the male screw on the external surface of the bearing housing 3 and the buffer length, that is , the length between an axle and the car body frame is varied by first loosening the lock nut 5 and rotating a tool while making contact to a pawl-shaped section on the upper end of the bearing section 3.