In the motor car, as far back as around 1970, the option in favour of using ball-joints with a long-life grease filling and an elastic sealing, was decided. This step is obviously not feasible in utility vehicles. This is probably because the, up to 50-times higher strain on the ball-joints, is simply not controllable, or they would have to be so large that the available space would not be sufficient. Apart from this, the rigid front axle requires only one joint, which moves only in one direction. Thus, truck front axles must still be greased and from time to time, depending on the work-load, the bushings must be replaced. Thereby, the bushings visible in the steering knuckle (see above figure) are exchanged, and the new kingpins are adapted by grinding.
As far as the front axle is concerned, one makes a distinction between the fork- and the stub axle. Both of these concepts always refer to the rigid axle casing. The fork axle is mostly found in driven- and the stub axle in non-driven rigid axles. The fork creates space for the drive shaft, whose joint must lie exactly in the steering-swivel axis. For this, in all cases, it requires a kingpin at the top and one at the bottom. 04/10