This document discusses key terms and concepts related to steering system design, including camber, caster, directional stability, geometric centerline, toe, parallelism, and Ackerman steering. It provides definitions and explanations of these terms. For example, it explains that caster provides directional stability and the ability of wheels to return to the straight ahead position after a turn. It also discusses various steering system types like rack and pinion steering and their advantages and disadvantages.

2. STEERING SYSTEM DESIGN
KEY TERMS
 Camber
 Caster
 Directional Stability
 Geometric Centerline
 Lead
 Parallelism
 Pull
 Steering Axis
 Thrust Angle
 Toe

3. CAMBER:-
 Camber is the inward or outward tilt of the
wheel when compared with a true vertical line.
 Camber is positive when the top of the wheel
is tilted out.
 Camber is negative when the top of the wheel
is tilted in.
 It is at zero when the wheel is vertical
(straight up and down). Front wheels usually
have small positive camber.

5. CASTER:-
 Caster is the forward or backward tilt of the
steering axis when compared with a true
vertical line.
 Caster is positive if the axis is leaning
rearward.
 Caster is negative if the axis is leaning
forward.
 It is zero when the steering axis is straight up
or down.
 Caster is measured in degrees. Most vehicles
 have a small amount of positive caster.

6. Caster gives the front wheels the ability to return to
the straight ahead position after a turn. Caster also
provides directional stability.
When a wheel is turned out, the spindle lowers and raises
the vehicle. When a wheel is turned in, the spindle raises
and lowers the vehicle.
When the wheels are released from a turn, the weight of
the vehicle helps move each spindle back toward the
mid-point until the load is equal on both front wheels.

8. 1)Caster angle 2)Kingpin inclination

9. High positive caster can also cause the wheels to return
to center very fast. A steering dampener is used in some
high caster applications to reduce the speed at which
the wheels return to center. Some vehicles use a
steering dampener to reduce the effects of having a
large amount of positive caster.

11. DIRECTIONAL STABILITY:-
 Directional stability is needed to keep vehicles
going ion a straight line or in line with the
direction of the steering wheel.
 Steering and suspension systems are closely
related, and in most cases, are dependent
upon each other.
 The steering system allows the driver to
direct the movement of the vehicle.
 The most common front steering systems are
the parallelogram and rack-and-pinion
steering systems.

12. TOE:-
 Toe is the difference between the front and rear
edges of a set of tires. When the wheels are
parallel to each other, toe is zero.
 When the front edges of the tires are closer
together, the tires are toed-in, and toe is
positive.
 When the rear edges are closer, the tires are
toed-out, and toe is negative.
 Toe is specified in degrees or inches.

14. GEOMETRIC CENTERLINE:-
 The vehicle’s geometric
centerline is formed
between the center of the
front wheels and the
center of the rear wheels.
 The geometric centerline
could also be drawn
through the midpoint of
the front and rear axles.
The geometric
 centerline is used as a
reference to align toe on all
four wheels.

15. THRUST ANGLE:-
 The thrust line is the direction
the rear wheels are pointing.
 If the rear suspension is not
damaged and the rear toe is
properly adjusted, the thrust
line and the geometric
centerline of the vehicle are the
same.
 The thrust angle is the
difference between the thrust
line and the geometric
centerline. A thrust angle to the
right is positive. A thrust angle
to the left is negative. Thrust
angle is measured in degrees.
 Thrust Angle = (Left Toe – Right
Toe) / 2

16. PARALLELISM AND CENTERLINE
STEERING
 Parallelism refers to the
wheels tread centerlines
being parallel to the
geometric centerline.
 The steering wheel is set
straight and the front toe is
adjusted to the thrust line,
which is now the
centerline.
 If toe is correct on the rear,
the front
 tires will follow a parallel
path with the rear, creating
centerline steering.

17. TREAD CENTERLINE
 On a vehicle that has front
and rear wheels equally wide
apart, the tread centerline is a
line from the midpoint of the
front tire tread to the
midpoint of the rear tire tread
on the same side. It should be
parallel to the geometric
centerline.
 If the tread centerline is not
parallel to the geometric
centerline, a cross-member
may not be positioned right,
or the cradle may be shifted
to the side.

19. Steering Ackerman:-
 Steering Ackerman
describes the angle
difference between the
outside and inside tire
of a vehicle
 The steering sensitivity
of the vehicle is greatly
affected by the amount
of Ackerman designed
into the suspension

20. Corner Conditions:-
 When the vehicle
negotiates a turn the
two front wheels must
carve different arc, the
outside wheel travels a
further distance than
the inner.

21. Drawing out Ackerman
 To visualize Ackerman
steering geometry you can
draw it out on the vehicle lay
out
 First draw a vehicle center
line
 Draw a line down the
center of the rear axle
 Then draw a line
intersecting the outer
steering point and the
kingpin axis
 The intersection of the two
dotted lines defines the
Ackerman characteristics of
the vehicle

22. Over True Ackerman
 Over Ackerman refers to the inside
tire turning more then the amount
required to travel the desired arc
 This case shows how the
intersection point falls in front of the
rear axle center line, thus increasing
the angle difference between the
two tires
 So it could be described as have toe
out in relation to the turning circle
 In most cases this is done for low
speed cars that require nimble quick
turning, the vehicle will have
increased steering response at low
speeds

23. Under True Ackerman
 In this setup the
intersection point falls
behind the axle center
 This causes the steering
response of the vehicle to
decrease slightly
 So it could be described
as have toe in in relation
to the turning circle

24. Anti-Ackerman
 This describes the
characteristic of the
outside wheel turning
more than the inside wheel
 This is done for high speed
stability, the car acts lazy
and does not respond
quickly to steering inputs
 This over stabilizes the
vehicle

25. Drawing Anti-Ackerman
 When drawing out Anti-Ackerman, imagine the Ackerman
drawing just mirrored around the front axle centerline
 The steering angle difference would be the same as normal
Ackerman, just that the outside tire is now turning more
then the inside

26. Requirements
On passenger cars, the driver must select the
steering wheel angle to keep deviation from
the desired course low.
 turns of the steering wheel;
 alteration of steer angle at the front wheels;
 development of lateral tyre forces;
 alteration of driving direction.

27. Damper strut front axle of a VW Polo (up to
1994) with ‘steering gear’,
long tie rods and a ‘sliding clutch’ on the
steering tube;
Damper strut front axle of a VW Polo (up to
1994) with ‘steering gear’,
long tie rods and a ‘sliding clutch’ on the
steering tube;

28. Steering system on rigid axles

29. If the movement curve 7 of the axle housing and curve 9 of the rear
steering rod joint do not match when the body bottoms out, the wheels can turn
and therefore an unwanted self-steering effect can occur.

30. Rack and pinion steering
Advantages disadvantages
• simple construction;
• greater sensitivity to impacts;
• economical and uncomplicated to
manufacture; • greater stress in the case of tie rod
• easy to operate due to good degree angular forces;
of efficiency;
• disturbance of the steering wheel is
• contact between steering rack and
pinion is free of play and even internal easier to feel (particularly in front-
damping is maintained (Fig. 4.10); wheeldrivers);
• tie rods can be joined directly to the • tie rod length sometimes too short
steering rack; where it is connected at the ends of
• minimal steering elasticity the rack(side take-off design, Fig.
compliance (Fig. 3.99); 3.67);
• compact (the reason why this type of
steering is fitted in all European and • size of the steering angle
Japanese front-wheel drive vehicles); dependent on steering rack travel;

31. Configurations
 There are four different configurations of this type of
steering gear (Fig. 4.8):
 Type 1 Pinion gear located outside the vehicle centre
(on the left on left-hand drive and on the right on
right-hand drive) and tie rod joints screwed into the
sides of the steering rack (side take-off ).
 Type 2 Pinion gear in vehicle centre and tie rods taken
off at the sides.
 Type 3 Pinion gear to the side and centre take-off, i.e.
the tie rods are fixed in the vehicle centre to the
steering rack.
 Type 4 ‘Short steering’ with off-centre pinion gear and
both tie rods fixed to side of the steering rack (Fig.
4.1).

32. The three most common
types of rack and pinion steering on
left-hand drive passenger cars.

34. Steering gear, manual with
centre tie rod take-off

35. Recirculating ball steering
Advantage Disadvantage
• Can be used on rigid • This type of steering system
axles. is more complicated on the
whole in passenger cars with
• Ability to transfer high independently suspended
forces. front wheels.
• A large wheel input angle • more expensive than rack and
pinion steering systems.
possible – the steering gear
• it sometimes has greater
shaft has a rotation range
steering elasticity, which
up to ±45°, which can be reduces the responsiveness
further increased by the and steering feel in the on-
steering ratio. centre range

36. Top view of the strut damper front
axle on a Mercedes vehicle.

37. Steering gear

38. Power steering systems
 Power steering systems have become more and
more widely used in the last few years.
 Manual steering systems are used as a basis for
power steering systems, with the advantage that
the mechanical connection between the steering
wheel and the wheel and all the components
continues to be maintained with or without the
help of the auxiliary power.
 The steering boost is thereby reduced, with the
aim of achieving better road contact at higher
speeds.

39. Hydraulic power steering
systems
 The method of using oil under pressure to boost
the servo is sophisticated and advantageous in
terms of cost, space and weight.
 This can be attributed to the hydraulic self-
damping.
 The oil pump is directly driven by the engine and
constantly generates hydraulic power.
 Depending on the driving assembly and pump
design, the additional consumption of fuel can lie
between 0.2 and 0.7 l per 100 km.

40. Component and Figure:-

41. Electro-hydraulic power steering
systems
 With electro-hydraulic power steering systems, the
power-steering pump driven by the engine of the
vehicle via V-belts is replaced by an electrically
operated pump.
 The pump is electronically controlled – when servo
boost is not required, the oil supply is reduced.
 The pressure supply unit (Fig. 4.19) can be
accommodated in an appropriate location (in
relation to space and crash safety considerations).
 Pressure-controlled systems generate only the
amount of oil required for a particular driving
situation.
 energy consumption is reduced to as little as 20%

42. 1 gear housing
2 piston with steering nut
3 steering spindle connection
4 steering shaft with toothed
segment
5 steering worm roller with valve
body
6 balls
7 recirculation tube
8 fluid flow limitation valve
9/10 valve piston
11/12 inlet groove
13/14 radial groove
15/16 return groove
17 fluid reservoir
18 torsion bar
19 hydraulic pump
20 pressure-limiting valve

43. Electro-hydraulic power steering system of the
Opel Astra (1997).
1 electrically operated power-steering pump
with integrated reserve tank (‘power
pack’)
2 pump–steering valve hydraulic lines
3 rack and pinion steering gear with external
drive, attached to auxiliary frame
4 steering valve.

44. Open-centre control system from ZF

45. Electrical power steering systems
 The bypass of the hydraulic circuit and direct
steering boost with the aid of an electric motor
has additional advantages in terms of weight.
 Engine bay space compared with electro-
hydraulic steering, because of the omission of all
the hydraulic components.
 more variations of the steering boost because of
the purely electrical signal processing.
 The systems only have limited power because
the current is limited by an operating voltage of
12 V.
 They are of interest though for smaller vehicles.

47. Electrical power steering system by ZF.

48. Steering column
 the steering column consists of the jacket tube
(also known as the outer tube or protective
sleeve), which is fixed to the body.
 The steering shaft, also called the steering tube.
This is only mounted in bearings at the top (or
top and bottom) and transfers the steering-
wheel moment MH to the steering gear.
 If the steering column does not align with the
extension of the pinion gear axis (or the steering
screw), an intermediate shaft with two universal
joints is necessary

49. Electric power steering system of the Opel
Corsa (1997).
1 steering-column assembly
2 steering column with
intermediate spindle
3 rack and pinion steering with
external drive.

50. steering tubes with flexible
corrugated tube portion

52. collapsible (telescopic) steering
tubes

53. Thank You