When replacing the clutch friction plate, it is strongly recommended to inspect the clutch pressure plate and thrust ring as well.
Over many years of use, the pressure plate and thrust ring are subjected to heat and wear. As a result, these components are often no longer perfectly flat and may become slightly "cup-shaped". This wear is usually difficult to see with the naked eye.
A new friction plate, however, is perfectly flat. If it is installed between worn mating surfaces, the contact area may be considerably smaller than intended. Instead of the clamping force being distributed evenly across the entire friction plate, the load becomes concentrated in a relatively small area.
In rare cases, this can create excessive local stresses in the friction plate and may lead to premature failure of the bond between the friction material and the steel core.
For this reason, BMW originally specified inspection of all clutch components whenever the clutch is serviced.
Recommendation:
- Inspect the pressure plate and thrust ring for wear, scoring, overheating and distortion.
- Replace or recondition worn components where necessary.
- Do not assume that a new friction plate alone will restore the clutch to as-new condition.
