Torsion Bar Suspension - Ball Joint Axle Beam
Mid America Motorworks 1966-1977 Narrowded Width Torsion Bar 319321
Article used with Permission: www.vw-resource.com
All pre-1968 and many 1968 and later Standard Beetles are equipped with torsion bar front ends, which was the original design of the Beetles front suspension. Super Beetles were made from 1971 to 1975 and had MacPherson Strut front suspension. Standard Beetles with the torsion bar suspension continued to be made through that period too, and continued to be made in Germany until 1986. The last Beetles were made in Mexico in about 2003, and these still have the stock torsion bar front suspensions. The earliest versions had grease nipples ("zerks") on the ball joints, but the ball joints were "sealed" after this time.
On torsion bar models, the front axle is a rigid beam with pivoting members that provide suspension movement, steering movement, and rotational movement of the wheels. This rigid beam is actually two large parallel steel tubes (“torsion arms” or Torsion bar tubes), one above the other, welded into a rectangular assembly with four stamped steel cross-members -- two cross-members on either side of the center point of the tubes, and one cross-member at each end of the tubes. The axle beam is bolted solidly to the frame head and includes two mounting points for the car body. These outer cross-members are known as side plates or "shock towers." They also serve as the upper mounting points for the shock absorbers.
Inside each of the torsion arms is a torsion bar, consisting of a set of ten spring-steel leaves (earlier models have fewer torsion spring leaves). The leaf spring sets are fixed at the inner end (bear the center of the torsion bar tubes) and the outer ends of the leaf springs are designed to twist to provide the spring function. The torsion bars are solidly bolted to each end of the torsion arms with set screws. Each half of each torsion bar has a torsion arm mounted at its outer end. In this way, all four torsion arms are sprung by only two torsion bars.
This torsion bar system prevents the transference of road shocks from one front wheel to the other and provides excellent resistance to the transference of road shocks to the suspension parts, chassis, and passengers.
Definition: A "torsion bar" is a part of the suspension consisting of a bar (or a set of spring-steel leaves) that twists, functioning as a spring and maintaining stability. Instead of the tempered metal rod being coiled, this springing member is firmly anchored at the inner at the ends on the vehicle frame, and affixed to the outer ends on the suspension. Thus, as the wheel moves up and down, the torsion bar twists, providing springing support.
On pre-1966 models, the outer ends of the torsion arms are attached to the steering knuckle with a pair of link-pins; on 1966 and later models, the torsion arms are attached with ball-joints.
Definition: A "ball joint" is a flexible swivel joint consisting of a ball within a socket. Ball joints act as pivots which allow turning of the front wheels and compensate for changes in the wheel and steering geometries that occur while driving. The ball joint is used primarily to connect the steering knuckle and tie rods to the control arm.
These ball-joints at the ends of the torsion arms provide a flexible mounting for the steering knuckles at each wheel. The ball-joints permit free vertical movement of the front wheels during bump and rebound and also allow the wheels to be turned around a vertical axis for steering. Front wheel camber adjustments are incorporated in the upper ball joint mountings.