Wilbers Fork Spring Zero friction Progressive Machine Gun Kelly Coloring Pages. Wilbers progressive fork springs friction" Friction reduction through fine grinding, resulting in ZERO friction. In vibratory finishing, the components to be machined, e. g. components, e. g. our fork springs, together with a specially together with a grinding wheel specially adapted for this in a vibrating container, the so called trough vibrator. The vibrations of the container generate a relative movement between the workpiece and the grinding wheel and, due to the constant rubbing against each other, lead to a smoothing of the component surface. At the end of the processing there is a fine, shiny surface. Particularly with our fork springs, this reduction of the surface roughness means a minimization friction = ZERO friction. Important is the combination with our specially developed Wilbers fork oil and the observance of the correct air chamber for the corresponding vehicle. Product may differ from the picture. Recommended viscosity and air chamber: