176 Auto Suspension and Steering
Ball sockets are used on other parts of the steering
linkage. The ball and socket section is often part of the
linkage component, and the entire component must be
replaced when the ball socket wears out.
Types of Steering Systems
Two main types of steering systems are used on
modern cars and light trucks: the rack-and-pinion system
and the conventional, or parallelogram linkage, steering
system. On automobiles, the conventional system was the
only type used until the 1970s. It has been almost
completely replaced by rack-and-pinion steering. Many
light trucks continue to use the conventional system. The
two types of systems are discussed below.
Note: The steering gear assembly is
referred to by many names. For clarity, we
will refer to the mating internal gears, the
related internal parts, and the housing as the steering
gear.
Steering Ratio
Steering ratio is the relative number of turns of the
steering wheel compared to the movement of the wheels.
If the steering wheel must be turned one revolution to turn
the front wheels one sixteenth of a turn, the steering ratio
is 1 to 1/16. Reversing the numbers gives a ratio of 16 to 1,
or 16:1. Although the steering ratio is not as critical on
modern vehicles with power steering, it must be carefully
selected as a compromise between handling and steering
effort. The average steering ratio on modern vehicles
ranges from 12:1 to 24:1. A heavy vehicle will have a
higher ratio than a lighter vehicle. If the vehicle has power
steering, the ratio will be lower than that on the same vehi-
cle with manual steering.
Steering ratio affects the response of the front wheels
to the movement of the steering wheel (handling) and the
ease of turning the wheel. A small steering ratio means that
slight steering wheel movement will turn the front wheels,
but the effort required to turn the steering wheel will be
relatively high. A large steering ratio means that more turns
of the steering wheel are needed to turn the front wheels,
but that the steering effort is less. A relatively high steering
ratio also helps to absorb shocks from the road. If for
instance the steering ratio is 16:1, road shocks are
transmitted to the steering wheel at 1/16 of their original
intensity.
Steering ratio, as well as overall handling and ease of
steering, is determined by many factors. The size of the
steering wheel was already mentioned. The relative size of
Steering gear
Frame
bracket
Pitman arm
stop bolt
Clearance
setting
Pitman
arm
Tie rod
Locknut
Cotter pin
Dust boot
Ball socket
Tension
spring
Grease fitting
Tie rod end
Housing
Nut
Figure 9-17. Adjustable pitman arm stop bolts and lock nuts.
This setup calls for a 0.20″ (5 mm) clearance for the proper
steering angle. (General Motors)
Figure 9-18. Cutaway view of a typical ball socket. Note the
internal components. (General Motors)
Threads
Taper
Tie rod end
Figure 9-19. Typical self-contained ball socket. Note the
tapered ball stud. (Moog)