The document discusses various components and principles of steering systems. It covers basic steering systems like linkage steering and rack-and-pinion steering. Linkage steering uses a gearbox, drop arm, center link, and track rods to connect the steering wheel to the wheels. Rack-and-pinion steering directly connects the steering wheel to the wheels using a rack and pinion gear and track rods. Ball joints and tie rods allow for suspension movement and steering. The Ackerman principle ensures the inner wheel turns through a greater angle on turns to avoid tire wear.

1. Steering Systems
Topics covered in this presentation:
 Basic Steering Systems
 Linkage Steering
 Rack-and-Pinion Steering
 Power Steering

2. The Steering System
 When the driver turns the steering wheel, the front and sometimes
the rear wheels move and the car turns the corner! From the drivers
point of view it is that simple, but many more things have to be taken
into consideration. For example –
 The effect of road surface irregularities
 Tyre behaviour under cornering stress
 An efficient mechanical system to give easy turning of the steering
wheel
 Driver fell must be maintained
 No (or very little) difference between empty and fully loaded
 The effect of accelerating or braking when the wheels are turned
 The front wheels should have a natural tendency to return to the
straight ahead position

3. The Steering System
 Imagine a car driving round a roundabout, the outer wheel has to
travel a greater distance than the inner, this is why a differential is
required in the transmission, it will be also noticed, that for the
steered wheels to maintain true running or rolling motion i.e. the
wheels must always be turning exactly end over end, much like a
coin rolling across the desk, if this was not the case, there would be
a scrubbing action ( the tyres would be dragged across the road
surface resulting in considerable wear), the inner wheel has to turn
through a sharper corner than the outer. This requirement is met by
the steering system through the use of special linkage between the
steered wheels, so each wheel is turned a slightly different amount,
so true rolling motion is maintained. This is known as the ‘Ackerman
Principle’ and is named after the person who invented it. The slight
change in the angles between the steered wheels is often referred to
as toe out on turns

4. Terminology
 The Steering Wheel – The Bit the driver holds on to! It also
incorporates the Air Bag.
 Steering Column – The shaft connecting the steering wheel to the
steering box or steering rack.
 Steering Rack – A combination of a small gear and a toothed rack.
This changes the rotation of the steering wheel into a back and forth
movement of the rack which in turn moves the road wheels.
 Steering Box – This does a similar job to the rack but needs extra
linkages and rods to connect it to the road wheels. Mostly used on
old cars, but still is in use on larger vehicles.
 Track rod/Tie rod – A rod to connect the left and right steered
wheels. The steering rack is also the track rod.
 Track rod end – A ball joint to allow steering and suspension
movement.
 Ball joint/Swivel joint – Part of the suspension, but these are joints
which allow the steered wheels to left and right.
 PAS – Power assisted steering. An engine driven pump or electric
motor, provides extra force to help the driver turn the steering.
 Tracking – toe in or toe out setting for the steered wheels.

5. Ackerman
Principle
Axle
Steering
Steering assembly at rest, the
longer bar represents the front
suspension axle, the shorter bar
is the steering linkage/mechanism.
Steering assembly
in operation, as the
steering linkage is
shorter than the axle,
the inner wheel is
turned through
a larger angle.
Ackermann stated the
principle that when a
vehicle travels in a
curved path, its wheels
should describe circles
around the same centre.
A wheel which follows a
markedly different path
will slide to some extent,
this would cause
excessive tyre wear. The
steering mechanism is
designed to insure that
when the vehicle turns
left or right, the inner wheel
is turned through a larger
angle to prevent tyre wear

6. Turning Radius (Ackerman Principle)
The steering system is designed to compensate for the different radiuses.
When turning, the inner wheels must turn on a tighter radius than the outer,
this helps avoid unnecessary tyre wear.
Toe-out is increased on turns.
Small adjustments can be made, but normally any error will result in worn or
damaged components being replaced.

7. Tracking – A steering adjustment which is used to insure that the
steered wheels are pointing straight ahead when the vehicle is moving
This setting is critical for tyre
wear. A small amount of Toe-in
helps compensate for the
effect of rear-wheel drive.
Zero “toe” effect is required when the
vehicle is moving. This helps reduce
tyre wear (scuffing or feathering).
Toe-in - The wheels point inward,
toward each other.
Toe-out - The wheels point
away from each other.
A small amount of Toe-out
is normal on front-wheel
drive vehicles.
Front Wheel Tracking

8. Steering Shafts and Columns
Nearly all steering systems use a steering column or shaft to link the driver
(steering wheel) to the steering rack or gear/box.
Bottom of steering column normally
has a master spline where it mounts
onto the steering rack-and-pinion or
steering gear/box.
Universal joints allow steering
shaft angles to change. Flexible
coupling
Universal
joints
Flexible coupling isolates steering
wheel from road shocks.
Steering
wheel
Steering rack
or gear/box
Most steering columns are
designed with a collapsible
section that helps prevent
forces generated in a collision
being transferred to the driver.
Collapsible
section
Master spline
location
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9. Linkage type uses a worm gear
inside the steering gear/box, this
operates the drop arm, then couples
to a centre link, idler arm, track rods
and the steering knuckles.
Basic Steering Systems
Rack-and-pinion type uses track
rods to couple the rack to the
steering knuckles.
Two main types of steering:
 Linkage or Conventional
type (also known as
Parallelogram).
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 Rack-and-pinion type.
Drop arm Idler arm
Track rods
Centre link
Steering knuckles
Steering
gear/box
Track rods
Rack-and-pinion

10. Rack-and-Pinion Type Steering System
Rack-and-pinion steering is more
precise and compact.
Uses less component parts.
Steering
knuckle
Steering
column
Ball joint
Steering rack
Track rod
Boot
More common on modern vehicles.
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11. Rack-and-Pinion Steering Principle
Pinion gear is turned by steering shaft.
Pinion meshes with rack to
move it sideways.
Thrust spring holds
rack against pinion to
prevent backlash.
Pinion shaft is normally shimmed to minimize end float
(up or down movement) also reducing backlash.
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12. Ball Joints
Ball joints are common on
most steering systems and
provide a controllable link to
the other steering components.
Suspension (vertical) and
steering (horizontal) movements.
Most steering rack ends have
adjustable ball joints and some
incorporate shock dampers.
Nearly all ball joints have some
form of adjustment.
Ball joint
Inner track
rod
Boot
Shock damper
assembly
Ball socket
Track rod
end
Adjusting thread
Adjusting
lock nut
Inner track
rod
Ball joints allow linkage
components to swivel freely.
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13. Linkage Type Steering System
Track rod
assembly
Track rod
assembly
Idler arm
bracket
Drop arm (connected to steering
gear/box)
Steering
damper
Centre link
Idler arm
Linkage type steering has many component
parts and is normally found on older vehicles.
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14. Worm gear type
Small number of teeth needed.
Steering Gear/box Principles
Drop arm couples to links.
Re-circulating ball mechanism.
Worm drive on steering shaft.
Most common are “Worm Gear”
and “Re-circulating Ball”.
 Worm Gear
 Re-circulating Ball
 Worm and roller (older Vehicles)
Most linkage type steering systems require some form of mechanical
advantage, this is provided mainly by the gear ratio in the steering gear/box.
Three main types of steering gear/box:
Re-circulating
ball type
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