1. Front wheels of the vehicle are mounted on front axles. It supports the weight of front part of the vehicle, facilitates steering, and absorbs shocks transmitted due to road surface irregularities. 2. There are different types of front axles including dead axles, live axles, and stub axles which connect to the front axle by king pins to allow steering of the front wheels. 3. The steering system includes components like the steering wheel, steering shaft, steering gearbox, steering linkage and wheels which work together to convert the rotational motion of the steering wheel into lateral motion of the wheels to steer the vehicle.

1. FRONT AXLE &
STEERING SYSTEM
CHAPTER:-2

2. Front Axle
■ Front axle carries the weight of the front part of the automobile as well as facilitates steering and
absorbs shocks due to road surface variations.
■ The front axles are generally dead axles, but are live axles in small cars of compact designs and also in
case of four-wheel drive.
■ The front axle is designed to transmit the weight of the automobile from the springs to the front
wheels, turning right or left as required.
■ To prevent interference due to front engine location, and for providing greater stability and safety at
high speeds by lowering the centre of gravity of the road vehicles, the entire centre portion of the
axle is dropped.
■ A live front axle contains the differential mechanism through which the engine power flows towards
the front wheels.
■ For steering the front wheels, constant velocity joints are contained in the axle half shafts.
■ Without affecting the power flow through the half shafts, these joints help in turning the stub axles
around the king-pin.

3. TYPES OF AXLES

4. ■ With a semi floating axle, the axle shaft both carries the weight and transmits torque
■ The wheel is often bolted directly to the flange on the axle
■ Semi float axles are seen on cars and light duty trucks
■ Semi floats are more limited in capacity, but lighter and cheaper to manufacture.
Semi Floating Axle

5. ■ The weight of the axle is supported by the axle housing-more specifically, a bearing spindle attached
to the axle housing, and a set of bearings in a separate wheel hub.
■ Torque is transmitted by a separate axle shaft that carries no weight.
■ As commonly built, full-floaters are considerably heavier, but also much stronger.
Full Floating Axle

6. ■ This type of axle is a combination of full and semi floating bearing.
■ In this bearing is locating between the axle casing and hub axle shaft do not have to withstand any
shearing or bending action due to the weight of the vehicle, which are taken up by the axle casing
through hub and bearing.
■ However it has to take the end loads and driving torque.
■ A three quarter floating axle is same as semi floating with one difference. The outer bearing is moved
to the outside of the outer end of the axle tube, supporting hub assembly via the bearing’s outer
circumference edge.
THREE QUARTER FLOATING AXLE

7. Front wheels of the vehicle are mounted
on front axles .
1. It supports the weight of front part of
the vehicle.
2. It facilitates steering.
3. It absorbs shocks which are
transmitted due to road surface
irregularities.
4. It absorbs torque applied on it due to
braking of vehicle.
FRONT AXLES

8. ■ Dead axles are those axles, which do not rotate.
■ These axles have sufficient rigidity and strength to take the weight.
■ The ends of front axle are suitably designed to accommodate stub axles.
Dead Axle

9. ■ Live axles are used to transmit power from gear
box to front wheels.
■ Live front axles although, resemble rear axles but
they are different at the ends where wheels are
mounted. Maruti-800 has line front axle.
Live Axle

10. ■ Stub axles are connected to the front axle by king pins.
■ Front wheels are mounted on stub axles arrangement for steering. Stub axle turns
on king pins.
■ King pins is fitted in the front axle beam eye and is located and locked there by a
taper cotter pin. Stub axles are of four types:
1. Elliot
2. Reversed Elliot
3. Lamoine
4. Reversed Lamoine
Stub Axle

11. TYPES OF STUB AXLES

12. Front Axle Construction
 The axle beam in use is of I or H-section and
is manufactured from alloy forged steel for
rigidity and strength.
 As compared to dead front axles, a totally
different type of swivelling mechanism is
used on the live front axle.
 To connect the wheel hub axles with driving
axle shafts, constant velocity joints are used
for the vehicles fitted with the front live
axles.
 Tracta, Rzeppa (or Sheppa) on Bendix
constant velocity or universal joints are
normally used.

13. Loading
 Front axles are subjected to both bending and shear stresses.
 In the static condition, the axle may be considered as a beam
supported vertically upward at the ends i.e. at the centre of the
wheels and loaded vertically downward at the centres of the
spring pads.
 The vertical bending moment thus caused is zero at the point of
support and rises linearly to a maximum at the point of loading
and then remains constant.
Thus the maximum bending moment = Wl, Nm
where, W = The load on one wheel, N
I = The distance between the centre of wheel and the spring
pad, m

15. CV-Joint Types
Outboard joint
Does not move in and out to change shaft length
Fixed joint
Inboard joint
Changes in length to allow movement of the suspension
Plunging joint

16. Outboard Joint Movement

17. CV-Joint Types
Inboard Joint Movement

18. CV-Joint Types

19. CV-Joint Types
Ball-type CV-joint
Was named after its designer, A.H. Rzeppa
Uses three to six steel balls held together by a steel cage
The balls ride in a socket to allow rotation and turning
Is used in most front-wheel-drive vehicles

20. Rzeppa Joint - Exploded View

21. Rzeppa Joint - Exploded View

22. CV-Joint Types
Tripod-type joint
Uses a central hub (tripod) with three trunnions
Has roller bearings that ride on the trunnions
The outer surface of bearings ride in the joint or “tulip” housing
Allows for greater angles

23. Tripod Joint

24. Outboard Joint Movement

25. Inboard Plunging Tripod

26. Inboard Plunging Tripod

27. Inboard CV Joints
Ball-type (Double-offset) Joint
•It Is similar to a Rzeppa joint but has elongated grooves in the inner race

28. Inboard CV Joints
Tripod-type joint
•Has longer grooves than a fixed-type joint to allow for plunging.

29. Inboard CV Joints
Cross Groove CV Joint
•The grooves in the outer race are cut at an angle to allow for better movement.

30. CV-Joint Types
Inboard Joint Movement

31. FWD Wheel Bearing Styles
■ Double-row, angular-contact
bearings
– Are used on most General
Motors, DaimlerChrysler,
and European cars
– Have two rows of ball bearings
located next to each other
■ Opposed tapered-roller bearings
– Are used on Fords and
most Asian cars

32. ■ The axle nut not only secures the end of the axle but it also sets the wheel bearing pre-load.
FWD Wheel Bearing Styles

33. Diagnosing CJ Joints & Axles
• Bad CV joints will generally make a clunking or clicking noise.
• Outer joints will make noise on turns.

34. Diagnosing CJ Joints & Axles
 Bad CV joints will generally make a clunking or clicking noise.
 Inner joints will make noise over bumps.

35. Perform a Road Test
■ Drive the car under various conditions such as accelerating, coasting, turning, and
weaving side to side
■ Listen for clicking or clunking, especially while turning
■ Feel for shudder, shimmy, vibration, or any other abnormalities

36. Visual Inspection
■ Check out all other problem areas before assuming that the problem is being caused
by the axle assembly
■ Check the CV-boots for tears and grease leaks
■ Check the shafts for damage or being bent
■ Move the shaft, wheels, and other components to check for looseness

37. Visual Inspection

38. Possible Reasons for CV-Boot Failure
■ Cuts or tears from foreign objects
■ Accident damage
■ Improper towing hook-up or service techniques
■ Ice forming around boot
■ Deterioration
■ Clamp failure

39. Off-Car Axle Inspection
■ Be careful not to overtighten the shaft
in the vise
■ Look for cracks, chips, pits, or rust on
all components
■ Check the joint for sticking while
plunging it in and out
■ Check for discoloring usually caused
by heat

40. Steering System
Function of Steering System
•Control of front wheel (sometimes
rear wheel) direction.
•Maintain correct amount of effort
needed to turn the wheels.
•Transmit road feel (slight steering
wheel pull caused by the road surface)
to the drivers hand.
•Absorb most of the shock going to the
steering wheel as the tire hits holes
and bumps in the road.
•Allow for suspension action.

41. ■ The steering mechanism should be very accurate ,easy to install and handle.
■ Driver’s effort should be minimum to steer.
■ It should provide maximum directional stability to vehicle.
■ It should multiply the turning effort applied on the steering wheel by driver with mechanical
advantage.
■ The steering system should not be affected by the side thrusts,cornering forces and wind effects.
Requirements Of A Good Steering System

42. ■ Factors related to wheels.
■ Steering linkages.
■ Steering geometry.
■ Suspension system.
Factors Which Influences The Stability & Control Of Vehicle
Are:-

44. Steering System
Turning the Car (when turning, front wheels don’t point the same direction)
•Inside wheel turns at a smaller radius, hence the inside wheel turns at a steeper angle then the
outside wheel.

45. Steering System
Linkage Steering System (Worm Gear)

46. Steering System
Linkage Steering System (Worm Gear) Parts
•Steering Wheel – used by the driver to rotate a
steering shaft that passes through the steering
column.
•Steering Shaft – transfers turning motion from
the steering wheel to the steering gearbox.
•Steering Column – supports the steering column
and steering shaft.

47. Steering System
Linkage Steering System (Worm Gear) Parts
•Steering Gearbox) – changes turning motion into a straight-line
motion to the left or right.
•Steering gear box ratios range from 15:1 to 24:1 (with 15:1, the
worm gear turns 15 times to turn the selector shaft once).
•Steering linkage – connects the steering gearbox to the
steering knuckles and wheels.

48. Steering System
Basic Rack-and-Pinion Steering

49. ■ The steering gear is a device for converting the rotary motion of the steering wheel into straight line
motion of the linkages with a mechanical advantage.
■ The steering gears are enclosed in a box called steering gear box.
ITS ADVANTAGES ARE:-
■ It reduces driver’s effort.
■ It assists in multiplying the effort applied applied at the steering wheel.
■ It makes steering move precise.
STEERING GEARS

50. Recirculating Ball - It is similar to worm and ball bearing nut
steering gear. The balls are contained in half nut and transfer
tube. As the cam or worm rotates the ball pass from one side of
nut through the balls along the track of the cam carries the nut
along with it and rotates to rocker shaft.
Rack and Pinion - A pinion is mounted on the end of the steering
Shaft. It engage with Rack which has ball joints at each end to
allow for the rise and fall of the wheels the rods connect the ball
joints to stub axles . The rotary movement of the steering wheel
rotates the pinion which moves the rack sideways.
VARIOUS TYPES OF STEERING GEARS

51. VARIOUS TYPES OF STEERING GEARS
CAM & PEG
WORM & BALL BEARING
WORM & SECTOR WORM & ROLLER
CAM & ROLLER

52. Steering System
Basic Rack-and-Pinion Steering
•Pinion Gear- rotated by the steering wheel and steering shaft; it’s teeth mesh with the teeth on the rack.
•Rack- long steel bar with teeth along one section; slides sideways as the pinion gear turns.

53. Steering System
Basic Rack-and-Pinion Steering
•Gear Housing- holds the pinion gear and rack.
•Tie-rods- connects the rack with steering
knuckles.

54. Basic Rack-and-Pinion Steering
•Part of rack contains a piston
•Two fluid ports, one on each side.
•The side with high pressure pushes the piston to the opposite side (turning the wheel).

55. Steering Linkage
Pitman Arm transfers gearbox motion to the steering linkage.
•Pitman arm is splined to the gearbox.

56. Steering Linkage
Center Link (Relay Rod) steel bar connects the right and
left side of the steering linkage.
•Connects to Pitman arm, Tie rod ends, and Idler arm.

57. Steering Linkage
Idler Arm supports the end of the center link on the
passenger side of the vehicle.
•Bolts to the vehicle’s frame.
•If worn, will cause excessive steering play.

58. Steering Linkage
Tie-Rod Assemblies: Two tie-rod assemblies are used to
fasten the center link to steering knuckles.
•Assembly is consist of inner tie-rod end, outer tie-rod end, and a
toe adjustment sleeve.
•Be sure to check the toe setting after replacing the tie-rod ends.

59. ■ steering gear ratio is the reduction ratio.
■ it is defined as the number of degrees that the steering wheel must turn to pivot the front
wheels through one degree.
■ In other words the overall steering ratio is defined as degrees of steering wheel angle divided
by corresponding front wheel angles.
Steering Gear Ratio
Steering Ratio = Steering wheel angle (deg) / Road wheel angle (deg)
Steering ratio for cars = 15 to 20
Steering ratio for trucks = 20 to 40

60. ON THE BASIS OF WHEEL INVOLVED IN STEERING.
■Two wheel steering.
■Two wheel steering is used to steer the two wheels of a vehicle.
■It is of two type
1. Front wheel steer – Front wheel make vehicle to steer.
2. Rear wheel steer – Rear wheel make vehicle to steer.
■All wheel steering.
4 wheel steering is the steering system in which all the 4 wheels
are used to steer the vehicle It is two types:
1. Active 4 wheel steering – It is the type of steering in which rear
and front moves in opposite direction. It is suitable for < 40 Km/h
speed.
2. Passive 4 wheel steering – It is the type of steering in which rear
and front moves in opposite direction. It is suitable for > 40 Km/h speed.
TYPES OF STEERING SYSTEMS

61. ■ Reversible steering.
■ Irreversible steering.
■ Semi-reversible.
ON THE BASIS OF TYPE OF WHEEL DRIVE & SUSPENSION IN VEHICLES.
■ Steering for rear wheel driven vehicles.
■ Steering for front wheel driven vehicles.
■ Steering for four wheel driven vehicles
■ Steering for rigid axle front suspension type vehicles.
■ Steering for independent front suspension type vehicles.
ON THE BASIS OF INTERACTING EFFECTS B/W STEERING WHEEL AND ROAD WHEELS

62. Power Steering is type of steering in which some
kind of External forces are used to reduce the
Driver’s Effort.
Forces can be enhanced by hydraulic & electric
forces
In Hydraulic power steering system a Hydraulic Ram
is created little ahead of the Rack which is connected
to Reservoir and the pump. When the wheel is
rotated the torsion bar along with steering shaft
revolves which cause a sudden flow of fluid in
Hydraulic Ram through Reservoir. This flow of fluid
decrease the Driver’s Effort.
In Electric power steering system a Torque sensor is
a sensor attached to the steering shaft which sense
the Driver’s force and according to that pass the
electricity to motors connected near Rack according
to the Driver’s Effort.
POWER STEERING

63. Power Steering normally use an engine driven pump and a hydraulic system to assist steering
action.
Three major types of power steering systems:
•Integral-piston linkage system.
•External power steering system.
•Rack-and-pinion system
•Integral power piston.
•External power piston.
Integral Rack-and-pinion system
is the most common.

64. Steering System
Power steering pump is driven by the engine produces the hydraulic pressure for steering
system operation.
Four basic pumps:
•Roller pump.
•Vane pump.
•Slipper pump.
•Gear pump.

65. Steering System Diagnosis
Steering Wheel Play is the most common problem.
Should not be able to turn the steering wheel
more than 1 ½’’ (33mm) without causing
movement of the front wheels.
Move the wheel side-to-side,
should have no play.

66. Steering System Diagnosis
Hard Steering (steering wheel requires excessive turning effort)
•Low power steering fluid.
•Pump belt broken or slipping.
Steering System Noise
•Belt squeal is a loud screeching sound produced by a worn belt.
•Power steering pump noise is usually a loud whine that only occurs when
the steering wheel is turned.
•Low fluid level and air in the system.
Check fluid with engine turned off.

67. TOE-IN, TOE-OUT
■Toe is the symmetric angle that each wheel makes with the longitudinal axis of the vehicle.
■Positive toe, or toe in, is the front of the wheel pointing in towards the centreline of the
vehicle.
■Negative toe, or toe out, is the front of the wheel pointing away from the centreline of the
vehicle.
■Toe can be measured in linear units, at the front of the tire, or as an angular deflection.

68. CAMBER ANGLE
Camber angle is the angle made by the wheels of a vehicle;
Specifically, it is the angle between the vertical axis of the wheels used for steering
and the vertical axis of the vehicle when viewed from the front or rear.

69. Camber Angle
■ Generally 2 degrees of positive camber angle is provided.
■ Positive camber angle results the tyre wear at out side edge
■ Negative camber results the tyre wear at inside edge
■ Equal camber on both wheels causes the vehicle to pullover the
road.
■ In right hand wheel drive country slightly high camber is provided
on right wheel than left wheel

70. King Pin Inclination, Included Angle, And Scrub Radius
KPI
• 7 to 8 degree
•Helps the straight ahead recovery
•Providing directional stability
•During the turning the vehicle body tends to up
Scrub radius
•Negative scrub radius tends to toe in
•Positive scrub radius tends to toe out
•Zero scrub radius tends to straight wheels- center point
steering
•Large scrub radius tends to need more torque to turn the
wheels
•Generally little bit positive scrub radius is preferred.

71. CASTER ANGLE
■Generally 3 degrees are provided
■Helps in direction of vehicle
■Positive castor tends to higher torque for
return steering and are provided in power
steering only
■Zero Caster or negative castor is provided in
manual steering.

73. Under Steer & Over Steer
■ Under steer is a term for a car handling condition in which during cornering
the circular path of the vehicle's motion is of a greater radius than the circle
indicated by the direction its wheels are pointed.
■ Oversteer is a phenomenon that can occur in an automobile while
attempting to corner or while already cornering. The car is said to oversteer
when the rear wheels do not track behind the front wheels but instead slide
out toward the outside of the turn.

74. Geometry at the Wheel
Center of
Tire Contact
Caster Angle
Kingpin Inclination Angle
Kinpin Offset at the Ground
Kingpin Axis

75. Lateral Inclination Angle
( ) sin sinzl zrM F F dλ λ δ= − + × ×
Fzr
F sin λzr
d
λ
F sin λzr
Fzr
δ
d sin δ

76. Torques from Lateral Inclination
4530150-15-30-45
-200
-100
0
100
200
Total
Steering Angle (deg)
SteeringTorque(in-lb)
STEERING TORQUE FROM
LATERAL INCLINATION ANGLE
Right Wheel (600 lb)
1" Offset
10° InclinationAngle
Left Wheel (800 lb)
M = - (F + F ) d sin λ sin δV zl zr
( ) sin sinzl zrM F F dυ λ δ= − +

77. Caster Angle
( ) sin coszl zrM F F dυ υ δ= − × ×
Fzr
F
sin ν
zr
d
ν
F sin ν
zr
Fzr
δ d cos δ

78. Torques from Caster Angle
4530150-15-30-45
-200
-100
0
100
200
Steering Angle (deg)
SteeringTorque(in-lb)
STEERING TORQUE FROM
CASTER ANGLE
Total
Left Wheel (800 lb)
Right Wheel (600 lb)
1" Offset
5°CasterAngle
M = (F - F ) d sin λ cos δV zl zr δυυ cossin)( ⋅⋅−= dFFM xrxl

79. Lateral Force
υtan)( rFFM yrylL ⋅+−=
Fyr ν
r tan ν

80. Tractive Force
dFFM xrxlT ⋅−= )(
Fxr d
λ

81. 4 Wheel Steer - Low Speed
R = δ (1 + δ /δ )frf
L
δ
R
L
f
δ
r
Turn
Center

82. 4 Wheel Steer - High Speed
δ
f
δ
r
ax
• Four-wheel in-phase steering
• Only at high speed (typically
above 35 mph)
• Rear steer angles less than
front
• Rear steer angles limited to a
few degrees

83. Steering System Applications
■ Effect of steering geometry on performance
– Understeer (linear range)
– Limit cornering (non-linear range)
■ Steering torques and feel
– On-center feel
– Torque gradients
– Linearity
– Power assist characteristics
– Friction and damping
■ Evaluate effects of asymmetry
– Manufacturing tolerance