between the flywheel and the pressure plate. There are
two types of pressure platesthe coil spring type and
the diaphragm type.
Coil spring pressure plate uses small coil springs
similar to valve springs (fig. 4-6). The face of the
pressure plate is a large, flat ring that contacts the
clutch disc during clutch engagement. The backside of
the pressure plate has pockets for the coil springs and
brackets for hinging the release levers. During clutch
action, the pressure plate moves back and forth inside
the clutch cover. The release levers are hinged inside
the pressure plate to pry on and move the pressure plate
face away from the clutch disc and flywheel. Small
clip-type springs fit around the release levers to keep
them rattling when fully released. The pressure plate
cover fits over the springs, the release levers, and the
pressure plate face. Its main purpose is to hold the
assembly together. Holes around the outer edge of the
cover are for bolting the pressure plate to the flywheel.
Diaphragm pressure plate (fig. 4-7) uses a single
diaphragm spring instead of coil springs. This type of
pressure plate functions similar to that of the coil
spring type. The diaphragm spring is a large, round
disc of spring steel. The spring is bent or dished and has
pie-shaped segments running from the outer edge to
the center. The diaphragm spring is mounted in the
pressure plate with the outer edge touching the back of
the pressure plate face. The outer rim of the diaphragm
is secured to the pressure plate and is pivoted on rings
(pivot rings) approximately 1 inch from the outer edge.
Figure 4-6.Coil spring pressure plate.
Figure 4-7.Diaphragm pressure plate operation.