Clutch: Description and Operation

3050 Clutch, 911 Carrera S (997)

The 911 Carrera S is provided with a self-adjusting clutch. This substantially extends the service life and ensures that the required amount of pedal pressure remains constant throughout the service life of the clutch.







Clutch linings are inevitably subject to wear. This, in turn, influences key parameters:
- The positions of the diaphragm springs alter in the course of time as the thickness of the lining diminishes. This results in an increase in contact pressure, release force, and, subsequently, the required pedal pressure.
- In order to compensate for the wear which occurs to the lining within the actuating system, the release system must include provision for the maximum possible wear distance. This increases the required axial space.
- Increasing the service life is of major importance. The possible working strokes of the diaphragm springs limit the scope for improving the service life of the linings via the use of thicker linings. A further increase in the wear thickness would lead to a decrease in contact pressure or would exceed the permissible level of stress on the material.

The self-adjusting clutch solves the above-mentioned problems by separating the lining wear from the diaphragm spring movement. The compensating mechanism continually registers the reduction in lining thickness and compensates the reduced distance resulting from the lining wear by turning an adjusting ring accordingly.







Pressure plate features:
- This mechanism requires only a small number of simple components:
- Two adjusting rings
- Two tension springs
- One retaining spring
- One wedge-shaped slide
- One housing stop

Each time the clutch is engaged, a stop checks whether any reduction has occurred in the lining thickness. If so, the stop lifts the retaining spring from the adjusting rings by precisely this wear distance, such that the slide can be pulled into the gap by its tension spring, thereby locking the retaining spring in this position. The next time the clutch is released, the diaphragm spring is able to take up its original position again - the clutch system has adjusted once again to its optimum force/travel condition.

Wear adjustment during a clutching operation.







The principle of wear compensation.







Wear compensation also taps reserves by reducing the maximum travel, as the release force characteristic which applies in new condition is maintained throughout the entire life of the clutch, thereby enabling higher torque transmission.