MG MGA Twin Cam Workshop Manual page 117

push-rod and the master cylinder piston, this automatic compensation for wear will always take place.
Should there be no free movement at this point, the master cylinder piston will not be allowed to return
fully to its stop and therefore the compensating orifice will be cut off.
Excessive pedal movement causes coil binding of the springs and imposes an undue load on the
bearing and on the crankshaft, causing excessive and rapid bearing wear. It therefore follows that the
required pedal travel is the sum of the two movements:
1. The free movement or travel necessary to take up the clearance between the master cylinder
push-rod and the master cylinder piston, provided to ensure that the clutch is fully engaged
when the foot is removed from the pedal. (See Section E.1.)
2. The effective movement, or travel necessary to release the clutch, i.e. the amount of effective
pedal movement necessary to move the release plate the distance required to free the clutch
completely.
If any difficulty is experienced in freeing the clutch when the correct release movement is provided, on
no account should efforts be made to improve matters by attempting to increase the effective pedal
travel. The actual cause of the trouble must be ascertained and rectified.
To obtain a clean release the release lever plate should move a distance of 5/16in. (8 mm.) towards
the flywheel.
Spring pressure
A tolerance of not more than 10 to 15 lb. (4.5 to 6.8 kg.) pressure is allowable on the compression load
of the operating springs when at their assembled height, and all clutch springs are tested for this
before assembly.
The clutch operating springs are not affected by high clutch temperatures, as the pressure plate
absorbs heat rapidly, the springs have only line contact, and a draught is continually passing under
them when the engine is running.
Tolerances
Wear on the working faces of the driven plate is about .001 in. (.02 mm.) per 1,000 miles (1600 km.)
under normal running conditions. The accuracy of the alignment of the face of the driven plate must be
within .015 in. (.38 mm.).
Fig. E.8 The use of the actuator to compress the clutch springs
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