Lotus Elise S1 Service Notes page 473

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QF.1 - GENERAL DESCRIPTION
The driving element of the clutch assembly consists of the rear face of the engine flywheel, and a pres-
sure plate fixed to the flywheel via the spring diaphragm clutch cover assembly. The driven element, is a
single, dry, double sided friction plate, splined to the gearbox input shaft, and interposed between the flywheel
and pressure plate. The diaphragm spring in the clutch cover clamps the friction plate between the pressure
plate and flywheel to provide the drive connection between engine and gearbox. The gearbox input shaft, on
which the friction plate is free to slide axially, is 'overhung' from the gearbox, with no spigot bearing in the rear
end of the crankshaft.
The hydraulic clutch release mechanism uses a master cylinder fixed to the pedal box, and a slave
cylinder mounted on a fabricated steel bracket attached to the transmission case. The master cylinder is
connected to the fluid reservoir of the brake master cylinder, and uses a flexible synthetic pipe (steel braided
on later cars) routed through the LN sill to connect to the slave cylinder. The slave cylinder operates a release
arm which is connected by shaft to the release fork inside the clutch housing. The fork presses the ball type
release bearing against the inner ends of the diaphragm spring fingers, which pivot about their fulcrums and
relieve the clamping force applied to the pressure plate via the diaphragm outer edge. The release bearing
slides on a guide sleeve surrounding the gearbox input shaft. A preload spring inside the slave cylinder applies
light pressure to the release lever in order to ensure that contact between the release bearing and diaphragm
spring fingers is maintained.
QF.2 - ADJUSTMENT
No routine adjustment of the clutch or release mechanism is required. The clutch slave cylinder is self
adjusting, with the 'rest' position of the piston dependent on the thickness, or degree of wear, of the friction
plate. As wear of the friction plate takes place, and its thickness is reduced, the slave cylinder piston is pushed
progressively further back on the return stroke with fluid being returned to the master cylinder reservoir.
The master cylinder pushrod length requires adjusting only on assembly in order to ensure:
a) the master cylinder piston is allowed fully to return under the action of its internal spring, and open the
port to the fluid reservoir;
b) maximum effective stroke of the cylinder is achieved.
The effective length of the pushrod can be adjusted by screwing the hexagonal pushrod into or out of the
pedal trunnion. Too much preload will not allow the reservoir port to open, whereas too much free play will not
allow sufficient fluid displacement and may induce a rattle from the pedal. To check the pushrod adjustment:
i) Remove the locking grub screw (3 mm key) in the side of the pedal trunnion, and apply Permabond A131
to the thread. Refit loosely.
ii) Screw the pushrod into or out of the trunnion until the pedal just contacts the pedal box flange (upstop).
iii) Apply V f e turn of preload to the pushrod, and tighten the trunnion lock screw to 5 Nm.
Clutch pedal
Trunnion
1037 I
1QQA / f l 9
Paae 3