Chapter 25 Steering Systems 499
• The linkage assembly connecting the
steering arms and steering gear.
• The steering wheel, steering shaft, and
steering gear assembly.
These assemblies are used in all steering
systems. The principles and components of each
assembly are discussed in the following sections.
Spindle and Steering Arm Assembly
When the front wheels are turned, the spindle
assemblies (sometimes called the steering
knuckles) swivel on the ball joints of a conven-
tional suspension system or on the ball joint and
upper bearing assembly of a MacPherson strut
assembly. The ball joints and other suspension
system components were discussed in Chapter 24,
Suspension Systems.
Spindle/Steering Knuckle
The part that attaches the front wheel rim
and tire to the frame is usually called the spindle
on rear-wheel drive vehicles, and the steering
knuckle on front-wheel drive vehicles. The spin-
dle is attached to the wheel rim and tire, as well
as the rotor. These parts rotate on the spindle.
The spindle is also the mounting surface for the
stationary brake components, such as the caliper
and pads or the backing plate, wheel cylinder,
and shoes. Macpherson strut and conventional
suspension spindle assemblies are shown in
Figure 25-3.
On front-wheel drive vehicles, the drive axles
attach to the wheels through a hole in the steering
knuckle. The drive axle support bearings are usu-
ally part of, or attached to, the steering knuckle.
The axle shaft rotates on the bearings to drive the
front wheel and tire. Figure 25-4 illustrates a front-
wheel drive steering knuckle.
Steering Arms
Figure 25-3 also shows the steering arms.
Most steering arms are forged as an integral
part of the spindle or steering knuckle, as shown
in the fi gure. Steering arms used on large trucks
may be bolted to the spindle. The outer ends of
the steering arms have a tapered hole to which
the tie rod end ball sockets are attached. When
the steering arms are moved to the right or
left, they force the spindle to pivot on the ball
joints or on the ball joint and strut top bearing,
depending on system design.
Steering Linkage
Linkage is necessary to connect the steer-
ing gear pitman arm to the steering arms. The
two linkages most commonly used today are
Spindle
Lower
suspension
ball joint
Tie rod end
Upper
suspension
ball joint
Drag link to
center link
tie rod end
Tie rod ends
Single post hoist
Pitman arm
to drag link
tie rod end
Upper
suspension
ball joint
Lower
suspension
ball joint
Tie rod end
Spindle
Drag link Center link Pitman arm
Figure 25-2.
A conventional steering linkage arrangement used on a rear-wheel drive pickup truck.
Dodge