LMB Hydraulic Clutch Bearings (HCB’s)

Many vehicles are now fitted with a Hydraulic Clutch Bearing (HCB), also known as Concentric Slave Cylinders (CSC’s) as opposed to the conventional release fork and bearing:


HCB Combined 2

The conventional method of operation of the clutch is by cable or hydraulic actuation of a release fork, this disengages the clutch via a release bearing. Hydraulic Clutch Bearings enable a lighter clutch pedal effort with better take-up, allowing vehicle manufacturers to dispense of the release fork, guide and bearing. The HCB is mounted inside the gearbox bell-housing and is usually made from either modern thermo-plastics or aluminium, with intricate rubber seals and chambers within.

After many clutch actuations the rubber seals become worn and the operating position within the chamber of the HCB changes, which means the worn internal components are no longer aligned. Therefore, when a clutch is replaced it is essential that the HCB is also replaced at the same time; as a result all LMB Clutch or Flywheel Replacement Kits come complete with a HCB if applicable.

It is imperative that the rubber seals inside HCB’s are of the highest quality to ensure there is no loss of hydraulic fluid. If fluid is allowed to pass through the seals it will contaminate the friction material on the disc, which will result in clutch failure.

The HCB MUST NOT be compressed prior to fitment; this will damage the rubber seals as they are not fully lubricated.