Air Springs
An identifying feature of the E65/E66 air spring is the internally guided air bellows. Internally guided means that the bellows is guided in an aluminum casing. The bellows is supported on this casing. This prevents the compression forces from weighing heavily on the bellows.
This process allows the bellows to be manufactured from a thin, flexible diaphragm which can react to minimal shocks and in this way provide a more comfortable suspension.
The diaphragm is composed of only one fabric layer embedded in rubber. The fibers within the fabric run longitudinally along the spring strut. The bellows is therefore known as an axial air bellows.
The bottom end of the air spring strut is enclosed in a bellows in order to protect the diaphragm against the mechanical effects of fouling (sand, dirt etc.). The lower end of the bellows incorporates small holes for pressure compensation in the space between the roll piston and bellows. The action of the bellows rolling in this space produces pressure differences.
The bellows together with the roll piston contains a volume of air that is sufficient for optimum suspension.
A residual pressure holding valve on the air spring strut prevents it from being depressurized. The air spring strut remains under pressure in the event of a loss of pressure in the system. The residual pressure is 3.25 +/- 0.75 bar. This ensures that the bellows is not damaged when the car is still being moved.
The residual pressure holding valve is secured with Loctite and must NOT be removed.
The air spring strut is initially filled at the manufacturer to 10 bar. This pressure is reduced to 3.5 bar when the spring strut is to be stored. Under this pressure, the strut is extended to maximum length.
The connection of the air spring struts to the air supply unit (distributor block) is located on the left of the luggage compartment under the flap on which the wheel nut wrench is mounted.