shape requires less space to operate in. Pads are
sometimes used between the spring and the chassis to
eliminate transferring vibrations to the body. Because
of its design, the coil spring cannot be used for torque
reaction or absorbing side thrust. Therefore, control
arms and stabilizers are required to maintain the proper
geometry between the body and suspension system.
This is the most common type of spring found on
modern suspension systems.
Coil spring mountings are quite simple in
construction. The hanger and spring seat are shaped to
fit the coil ends and hold the spring in place. Cups that
fit snugly on each coil end are often used for mounting.
The upper cup can be formed within the frame, in the
control arms, or part of a support bracket rigidly fixed
to the cross member or frame rail. The lower cup is
fastened to a control arm hinged to a cross member or
frame rail. Rubber bumpers are included on the lower
spring support to prevent metal-to-metal contact
between the frame and control arm, as the limits of
compression are reached.
The leaf spring acts as a flexible beam on
self-propelled vehicles and transmits the driving and
breaking forces to the frame from the axle assembly.
Leaf springs are semi-elliptical in shape and are made
of high quality alloy steel. There are two types of leaf
springssingle leaf and multileaf (fig. 8-11). The
single leaf spring, or monoleaf, is a single layer spring
that is thick in the center and tapers down at each end.
Single leaf springs are used in lighter suspension
systems that do not carry great loads. A multileaf
spring is made up of a single leaf with additional
leaves. The additional leaves make the spring stiffer,
allowing it to carry greater loads.
The most common type is the multileaf spring (fig.
8-12) that consists of a single leaf with a number of
additional leaves attached to it using spring clips.
Spring clips, also known as rebound clips, surround the
leaves at intervals along the spring to keep the leaves
from separating on the rebound after the spring has
been depressed. The clips allow the springs to slide,
but prevent them from separating and causing the
entire rebound stress to act on the master leaf. The
multileaf spring uses an insulator (frictional material)
between the leaves to reduce wear and eliminate any
squeaks that might develop. To keep the leaves equally
spaced lengthwise, use a center bolt for the multileaf
spring. The center bolt rigidly holds the leaves together
in the middle of the spring, preventing the leaves from
moving off center. Each end of the largest leaf is rolled
into an eye, which serves as a means of attaching the
spring to the vehicle. Leaf springs are attached to the
vehicle using a spring hanger that is rigidly mounted to
the frame in the front and the spring shackle in the rear,
which allows the spring to expand and contract without
binding as it moves through its arc. Bushings and pins
provide the bearing or support points for the vehicle.
Spring bushings may be made of bronze or rubber and
are pressed into the spring eye. The pins that pass
Figure 8-10.Coil springs.