An improved adjustable pneumatically operated cylinder for use on exercise equipment or chairs is particularly equipped with an external tube in which a piston and an adjustable piston are disposed head to head so as to form a variable air chamber therebetween. The adjustable piston is connected to an adjustment bolt which can be adjusted relatively with respect to an adjustment base fixed to the bottom of the external tube so as to make the adjustable piston move upward to reduce the size of the air chamber, resulting in the increase of the air pressure therein or downward to increase the size of the air chamber, resulting in the decrease of the air pressure. Thereby, the operation pressure of the cylinder can be properly adjusted according to practical requirements.
A torsion beam axle suspension is provided, in which a shock absorber is directly mounted on right and left trailing arms and is further mounted to the mount by a ball joint. Thus, it is possible to reduce the weight and production expenses, thus to enhance productivity. Further, it is possible to considerably decrease a friction caused by movement of the shock absorber even though the transverse force is applied, thus to enhance the riding comfort.
