Steering Systems - Level 1 IMI

​Steering Systems

◼ identify the different types of steering systems used in modern vehicles

Steering Systems

In this presentation you will:

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The purpose of the
steering system is to
allow the driver to
control the direction
of a vehicle when it
is moving.

Purpose of a Steering System

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Early vehicles with
steering wheels
were fitted with
linkage type
steering systems.

Most modern
vehicles are fitted
with rack and pinion
steering systems.

When turning a corner, the driver turns a steering wheel. This turning motion
is transferred to the front road wheels.

The direction the front wheels point is the direction the car will travel, so long
as the wheels do not lose grip.

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Turning a Corner

The driver turns a steering
wheel to control the
direction of the vehicle.

A steering shaft connects
the steering wheel to the
steering components.

Steering systems use a
steering column to link
the driver to the steering
components.

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Steering Columns

Steering shaft

Steering wheel

Universal joints allow
the steering shaft to
change angles.

Most steering columns
are designed with a
collapsible section that
helps prevent the
forces generated in an
accident being
transferred to the
driver.

The bottom of the
steering shaft
connects to the
steering components
(rack or box).

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Steering Columns

Universal joints

Connection to steering

components

Collapsible

section

Steering shaft

Steering wheel

There are two
main types of
steering system:

◼ Linkage

◼ Rack-and-pinion

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Steering Types

Multiple Choice

Two technicians are discussing the driver’s role in the steering system.

Technician A states that the driver controls the steering system by turning a steering wheel.

Technician B states that steering columns are designed to collapse in an accident to help protect the driver.

Who is correct?

• Only technician A

• Only technician B

• Both technician A and technician B

• Neither technician A nor technician B

Answer : Both Technician A & B​

Both of the technicians are correct. The driver does control the steering by using a steering wheel, and most steering columns are designed to collapse in the event of an accident.

Steering wheel

The steering wheel is
used by the driver to turn
the steering components.

The rack-and-pinion
steering is more
compact and precise,
as it uses fewer parts
and has a more direct
path to the wheels than
the linkage type.

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Rack-and-Pinion Steering Systems

The steering column
with pinion gear on the
end connects the
steering wheel to the
rack assembly.

Steering
column

To pinion

gear

The steering rack assembly changes rotary motion of the pinion gear into
linear motion.

As the pinion gear rotates, the steering rack is moved left and right.
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Rack-and-Pinion Steering Systems

Pinion gear

Rack

Track rods are
attached to the ends
of the rack.

The gaiter, a flexible
usually rubber tube,
covers the joint between
the rack and track rods
to stop dust and dirt
getting in the rack.

Track rod

Gaiter

Gaiters are sometimes
called boots.

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Rack-and-Pinion Steering Systems

They connect the rack
to the hub carrier.

The hub carrier
transfers movement of
the rack, via the track
rods, into a change of
wheel angle.

Hub carrier

King pin
(swivel pin)

Lower ball joint

Track rods connect to
the hub carrier via a
lower ball joint.

It rotates about an
axis created by the
king pin (swivel pin).

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Rack-and-Pinion Steering Systems

To make the front wheels
turn, a pinion gear, which
is attached to the steering
column shaft, rotates as
the driver turns the
steering wheel.

The pinion gear meshes
with the rack, and as the
pinion gear rotates the
rack moves sideways.

This sideways movement
is transferred to the
wheels, via the track rods
and hub carriers, causing
them to change angle.

Rack assembly

(rack inside)

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Rack-and-Pinion Steering Operation

Steering gear
(pinion gear inside)

◼ Steering box - converts

rotary motion of the
steering shaft into
angular linear motion of
the pitman arm

◼ Steering shaft - used to

connect the steering wheel
to the steering components

◼ Steering wheel - used

by the driver to turn the
steering components

The linkage steering system
consists of several linked
components, which are:

◼ Pitman arm - connects

the steering box to the
drag link
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Linkage Steering System

Steering wheel

Steering shaft

Steering box

Pitman arm

Drag link

Drag link

The drag link joins the left and right sides of the steering system, causing
them to move together.

The drag link is sometimes called a relay rod or track bar.

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Linkage Steering System

The pitman arm moves the drag link in the required direction
(left or right), and this movement is transferred to the track rods
on each end of the drag link.

In a linkage steering system, the driver turns the steering wheel.
Which in turn, through the steering box, swings the pitman arm.

Steering box

Drag link
Track rod

Pitman arm

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Linkage Steering System Operation

Multiple Choice

Two technicians are comparing rack-and-pinion and linkage steering systems.

Technician A says rack-and-pinion steering systems provide a more direct route from the driver to the road wheels as there are fewer parts.

Technician B says linkage steering systems use a rack to create the linear movement that causes the wheel angle to change.

Who is correct?

• Only technician A

• Only Technican B

• Both Technician A & B

• Neither Technician A or B

Answer : Technician A​

A linkage steering system does not use a rack to create linear movement.

Inner wheel

Outer wheel

Non-Ackermann

20°

20°

Front inner

wheel

Front outer

wheel

Vehicle Direction

Ackermann

20°

35°

Front inner

wheel

Front outer

wheel

Vehicle Direction

When a vehicle turns
a corner, the outer
wheel will travel a
greater distance than
the inner wheel.

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Steering Geometry

The inner wheel
needs to turn through
a greater angle than
the outer wheel so it
does not slip.

The Ackermann
steering geometry
allows each front
wheel to turn through
a different angle.

Multiple Choice

The Ackermann steering geometry causes what to happen when a vehicle turns a corner?

• The inner wheel is turned through a greater angle than the outer wheel

• Both the inner and outer wheels are turned through the same angle

• The outer wheel is turned through a greater angle than the inner wheel

• The inner wheel turns at the opposite angle than the outer wheel

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Question 3

The Ackermann steering geometry turns the inner wheel through a greater
angle than the outer wheel. This is needed because the inner wheel has a
tighter radius to follow.

A) The inner wheel is turned through a greater angle than the outer wheel

B) Both the inner and outer wheels are turned through the same angle

C) The outer wheel is turned through a greater angle than the inner wheel

The Ackermann steering geometry causes what to happen when a
vehicle turns a corner?

​Answer : The inner wheel is turned through a greater angle than the outer wheel.

The Ackermann steering geometry turns the inner wheel through a greater angle than the outer wheel. This is needed because the inner wheel has a tighter radius to follow.

The additional force
applied to the steering
can be generated
hydraulically or
electronically.

Power steering assists
the driver by reducing
the amount of effort
needed to turn the
steering wheel.

This is particularly
useful when the vehicle
is moving slowly.

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Power Steering

Power steering

pump

Power steering rack

High pressure

fluid lines

Steering assistance is
provided by an electric
motor directly
connected to the rack.

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Electromechanical Power Steering - Servoelectric

This is a much simpler
system as it removes
the need for a pump,
hosing, reservoir and
hydraulic fluid.

The control unit
operates the motor
by using sensory
feedback on steering
torque, vehicle
speed, engine speed,
steering angle and
steering speed.

Steering torque

Steering angle

Engine speed

Vehicle speed

Steering speed
Control

unit

Electric motor

If the vehicle is moving quickly, for example changing lanes on a highway,
less power assistance is provided.

Some systems dynamically change the amount of power assistance
depending on vehicle speed.

If the vehicle is moving slowly, for example when parking, a large force is
provided by the power assistance.

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Power Steering - Servotronic

More power assistance

Less power assistance

Alternatively, some
reservoirs use a dipstick
to indicate the fluid level.

Some vehicles have a
clear reservoir where
the power steering fluid
can be seen.

The level should be
between the minimum
and maximum
indicated levels.
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Power Steering Fluid Check and Top Up

Minimum

Maximum

Dipstick

​The fluid level is checked against the markings on the side of the reservoir.

The fluid should be
either clear or pink,
showing good condition.

The colour of the
power steering fluid
can indicate if there
is a problem.

It is common for power
steering fluid to turn orange.

If it is very dark or has a
burned smell then it will
need replacing.

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Power Steering Fluid Check and Top Up

Summary

◼ the need for a steering system

In this presentation you have seen:

◼ linkage steering components and operation

◼ rack-and-pinion steering components and operation

End