a suspension apparatus has suspension units mounted on wheels and each unit has a fluid spring chamber . fluid is supplied to contracted fluid spring chambers and is exhausted from elongated fluid spring chambers to control the change in position of the vehicle . in the position control mode , a large - diameter path is selected to supply or exhaust a large amount of compressed fluid . in the height control mode , a small - diameter path is selected to supply or exhaust a small amount of compressed fluid . the required amounts of compressed fluid can be supplied to the fluid spring chambers in both the position and height control modes .