The suspension system connects a vehicle to its wheels and serves two main purposes - contributing to handling and braking safety while also providing a comfortable ride by isolating the vehicle from road bumps and noise. An effective suspension balances these goals. Most modern vehicles use independent front and rear suspension systems with springs, shock absorbers, and linkages to enable each wheel to move independently without affecting the others, improving both ride and handling. The suspension aims to separate the energy of vertical wheel movements from the vehicle body.

1. 1

2. Suspension Introduction
•Suspension is the term given to the system of springs, dampers
(shock absorbers) and linkages that connects a vehicle to its
wheels.
•Suspension systems serve a dual purpose – contributing to the
car's handling and braking for good active safety and keeping
vehicle occupants ‘comfortable’ and reasonably well isolated from
road noise, bumps, and vibrations
.
•These goals are generally at odds, so the tuning of the suspension
involves finding the right compromise. The suspension also protects
the vehicle itself from damage and wear.
•The design of front and rear suspension of a car may be different
from one another.

3. Suspension System
• So a suspension linkage system of some sort is needed to
enable the wheel to move up & down vertically.

4. Two
Perspectives
•RIDE – Also known as Isolation
•Ability to smooth out a bumpy road
•HANDLING – Also know as control
•Ability to safely accelerate, corner & brake

5. The purpose of the suspension is to provide the vehicle with
the following:
1. A smooth ride
2. Accurate steering
3. Responsive handling
4. Support the weight of a vehicle
5. Maintain acceptable tire wear
Purpose

6. Desirable Characteristics
• Minimize response to external disturbances.
• Ensure satisfactory control response characteristics.
• Ensure no major or uncontrollable instabilities.
• Provide satisfactory information flow to the driver.
• Remain consistent in behaviour with changing environmental factors
such as rough surface, change in surface coefficient etc.

7. Main Types
Dependent – when a solid axel is used - movement at one wheel
will in some way affect the opposite wheel – older cars and
commercial vehicles.
Advantages - simple construction and almost eliminates camber
change reducing tyre wear
Independent – Each wheel is free to react to whatever change in
surface without directly affecting the others – most modern cars.
Advantages - Better ride & handling

8. Suspension Change Effects
Suspension travel results in changes in wheel orientation which can
cause steer effects, other than those input by the driver.
• Scrub
• Camber
• Castor
• Aligning torque
• (anti-dive geometry can promote castor change)
• Vertical travel of the unsprung mass - bump steer
• Roll of the sprung mass - roll steer
• Drive torque
• Flexibility of the suspension mechanism can cause compliance

9. Sprung and Unsprung Masses
•Sprung Mass – All that part of the vehicle which is carried
by the components of the suspension.
•Unsprung Mass - The parts of the vehicle that move
directly according to the contours of the road.

10. Unsprung Weight
• A suspension system has to be designed to allow the wheels to
move up and down quickly over bumps and dips without affecting
the entire weight of the car or truck.
• This weight is called unsprung weight.
• For best handling and ride, the unsprung weight should be kept as
low as possible.
• Sprung weight is the term used to identify the weight of the car or
truck, which does not move up and down and is supported or
sprung by the suspension.

11. Overall Function
•Uneven nature of road surface causes vertical acceleration of
unsprung mass.
•Suspension allows the sprung mass to ride relatively undisturbed
while the unsprung mass follows the contours of the road.
•I.E. Suspension system separates the energy of the vertical
acceleration of the wheels from the body

12. Suspension Terms
Heave – normally when both wheels are moving up in relation
to the chassis
Bump – one or more wheels moving upwards in relation to the
chassis
Rebound – when the wheel is moving down in relation to the
chassis
Roll – The movement of the chassis in relation to the wheels

13. • Early suspension systems on old horse wagons, buggies, and
older vehicles used a solid axle for front and rear wheels.
Types of Suspensions

15. Independent Suspension
• Most vehicles today use a separate control arm-type of
suspension for each front wheel which allows for movement of
one front wheel without affecting the other front wheel.
• This type of suspension is called independent front suspension.

16. Springs
• A suspension spring serves two purposes.
• First, it acts as a buffer between the suspension and
frame to absorb vertical wheel and suspension
movement without passing it on to the frame.
• Second, each spring transfers part of the vehicle
weight to the suspension component it rests on, which
transfers it to the wheels.

17. Spring Materials
Most springs are made of a tempered steel alloy known as spring
steel, usually chrome silicon or chrome-vanadium alloy.

18. COIL SPRINGS
Coil springs are made of special round spring steel wrapped in a helix
shape. The strength and handling characteristics of a coil spring
depend on the following.
1. Coil diameter
2. Number of coils
3. Height of spring
4. Diameter of the steel coil that forms the spring

20. • The larger the diameter of the steel, the “stiffer” the
spring.
• The shorter the height of the spring, the stiffer the
spring.
• The fewer the coils, the stiffer the spring.
Continued…

21. • Springs are designed to provide desired ride and
handling and come in a variety of spring ends.

22. Spring Rate
• Spring rate, also called deflection rate, is a value that
reflects how much weight it takes to compress a spring
a certain amount.
• A constant-rate spring continues to compress at the
same rate throughout its complete range of deflection.

24. • A variable-rate spring may compress one inch
under a 100-pound load, but only compress an
additional half an inch under a 200-pound load.

25. • Before a spring is installed on a vehicle or any load is placed on it,
it is at its uncompressed length, or free length.
• Once installed, the weight of the corner of the vehicle resting on
the spring is called its static load.

26. Coil Spring Mounting
• Coil springs are usually installed in a spring pocket or spring seat.
• Hard rubber or plastic cushions or insulators are usually mounted
between the coil spring and the spring seat.

27. Spring Coatings
• All springs are painted or coated with epoxy to help
prevent breakage.
• A scratch, nick or pit caused by corrosion can cause a
stress riser that can lead to spring failure.

28. Instead of cutting springs to lower a vehicle, there are several
methods available that are preferred if the vehicle must be
lowered:
1. replacement springs
2. replacement spindles

29. Leaf Springs
• Leaf springs are constructed of one or more strips of long, narrow
spring steel.
• These metal strips, called leaves, are assembled with plastic or
synthetic rubber insulators between the leaves, allowing freedom
of movement during spring operation.

30. • The ends of the spring are rolled or looped to form eyes.
Rubber bushings are installed in the eyes of the spring
and act as noise and vibration insulators.

31. The leaves are held together by a center bolt, also
called a centering pin.

32. • One end of a leaf spring is mounted to a hanger with a bolt and rubber
bushings directly attached to the frame.
• The other end of the leaf spring is attached to the frame with movable
mounting hangers called shackles.

33. Rebound or spring alignment clips help prevent the
leaves from separating whenever the leaf spring is
rebounding from hitting a bump or rise in the roadway.

34. • Single leaf steel springs, called mono leaf, are used on
some vehicles.
• A single or mono leaf spring is usually tapered to
produce a variable spring rate.

35. To provide additional load-carrying capacity,
especially on trucks and vans, auxiliary or helper
leaves are commonly used.

36. Composite Leaf Springs
• Fiberglass-reinforced epoxy plastic leaf springs have
been used on production vehicles.
• Using 70% fiberglass with 30% epoxy composite.
• Leaf spring rate increases when the thickness
increases, and decreases as the length increases.

38. A torsion bar is a spring which is a long, round, hardened
steel bar similar to a coil spring except for a straight bar.
Torsion Bars

39. • One end is attached to the lower control arm of a front
suspension and the other end to the frame.
• When the wheels hit a bump, the bar twists and then
untwists.

41. Suspension Principles
1. Transverse (or side-to-side) wheel support. Transverse links are
also called lateral links.

42. 2. Longitudinal (front-to-back) wheel support.
Some suspension designs use an additional member to control
forward-back movement

43. Steering Knuckles
A steering knuckle is hard to classify either as part of the suspension
or as part of the wheel. A knuckle serves two purposes:
To join the suspension to the wheel
To provide pivot points between the suspension and wheel

44. The only knuckle that uses a kingpin is a steering knuckle
on an I-beam or twin I-beam front suspension.
The steering axis is the vertical center of the kingpin.

45. A control arm is a suspension link that connects a
knuckle or wheel flange to the frame.
Control Arms

46. Ball joints are actually ball-and-socket joints, similar to
the joints in a person's shoulder. Ball joints allow the
front wheels to move up and down, as well as side to
side (for steering).
Ball Joints

47. • If the coil spring is attached to the top of the upper control arm,
then the upper ball joint is carrying the weight of the vehicle and
is called the load-carrying ball joint.
• The lower ball joint is called the non load carrying or follower ball
joint.

48. If the coil spring is attached to the lower control arm, then the
lower ball joint is the load-carrying ball joint and the upper
joint is the follower ball joint.

49. Ball Joint Design
There are two basic designs of ball joints:
1.Compression Loaded
2.Tension Loaded.
A ball joint that does not support the weight of the vehicle and
acts as a suspension pivot is often called a follower ball joint or
a friction ball joint.

51. Some vehicles are equipped with round steel rods which are
attached between the lower control arm at one end and the
frame of the vehicle with rubber bushings, called strut rod
bushings, at the other end.
Strut Rods

52. Continued…
• Strut rods are also called tension or compression
rods or simply TC rods.
• Some vehicle manufacturers call the strut rod a drag
rod because it was attached in front of the wheels, and
therefore acted on the lower control arm as if to drag
the wheels behind their attachment points.

53. • If a strut rod has a nut on both sides of the bushings,
then the strut rod is used to adjust caster.

54. Stabilizer Bars
• Most cars and trucks are equipped with a stabilizer bar on the front
suspension, which is a round, hardened steel bar (usually SAE 4560
or 4340 steel) attached to both lower control arms with bolts and
rubber bushing washers called stabilizer bar bushings.

55. • A stabilizer bar is also called an anti-sway bar (sway bar) or anti-roll
bar (roll bar).
• A stabilizer bar operates by twisting the bar if one side of the vehicle
moves up or down in relation to the other side, such as during
cornering, hitting bumps, or driving over uneven road surfaces.

56. Stabilizer links connect the ends of the stabilizer bar to
the lower control arm.

57. • The Stablizer bar pulls down on the mounting bushing when the
vehicle is hoisted off the ground, allowing the front suspension to drop
down.
• These bushings are a common source of noise, especially when cold.
• Lubricating the bushings with paste silicone grease often cures the
noise

58. Shock Absorbers
• Shock absorbers are used on all conventional suspension systems to
dampen and control the motion of the vehicle's springs.
• Without shock absorbers (dampers), the vehicle would continue to
bounce after hitting bumps.
• The major purpose of any shock or strut is to control ride and handling.
• Standard shock absorbers do not support the weight of a vehicle.
• The springs support the weight of the vehicle; the shock absorbers
control the actions and reactions of the springs.
• Shock absorbers are also called dampers.

61. • Some vehicles such as Ford Mustang use four shock absorbers on
the rear suspension. The vertical shock absorbers control vertical
body movement with the rear coil springs.
• The longitudinal shocks help control rear axle during acceleration
and deceleration.

62. • As a wheel rolls over a bump, the
wheel moves toward the body
and compresses the spring(s) of
the vehicle.
• As the spring compresses, it stores
energy.
• The spring then releases this
stored energy, causing the body of
the vehicle to rise (rebound).

63. The hydraulic shock absorber operates on the principle of
fluid being forced through a small opening (orifice).
Shock Absorber Operation

65. Gas-Charged Shocks
• Most shock absorbers on new vehicles are gas
charged.
• Pressurizing the oil inside the shock absorber helps
smooth the ride over rough roads.
• This pressure helps prevent air pockets from forming in
the shock absorber oil as it passes through the small
passages in the shock.

66. • Some gas-charged shock absorbers
use a single tube that contains two
pistons that separate the high-
pressure gas from the working
fluid.
• Single tube shocks are also called
monotube or DeCarbon after the
French inventor of the principle
and manufacturer of suspension
components.

67. Remote reservoir shock absorbers are units designed for heavy-duty use
that use a separate container for the working fluid.
Remote Reservoir Shocks

68. Air Shocks/Struts
• Air-inflatable shocks are standard shock absorbers with an air chamber
with a rubber bag built into the dust cover (top) of the shock.
• Air-inflatable shock absorbers or struts are used in the rear of vehicles to
provide proper vehicle ride height while carrying heavy loads.
• A rubber tube forms an inflatable air chamber at the top of an air shock
• The higher the air pressure in the chamber, the stiffer the shock

70. Air Springs
• Some electronically controlled suspension systems use air springs.
• A basic air spring consists of a rubber air chamber, generally
closed at the bottom by a piston fitted into a control arm, or by a
strut shock absorber.

71. Continued…
• Some air springs are in effect
auxiliary springs inside a coil-
spring strut.
• In these designs, the coil spring
supports the weight of the
vehicle, while the air spring raises
or lowers the body to adjust ride
height according to load.

72. A coil-over shock absorber uses the
force of an external coil spring to boost
the performance of the basic shock
absorber.

73. Hydraulic Shock Absrober
• A coil-over shock absorber uses the force of an external coil
spring to boost the performance of the basic shock absorber.
• A coil-cover shock is a standard hydraulic shock absorber with a
coil wrapped around it to increase stiffness and to take some of
the carrying weight off the spring.

74. Struts
• A strut is a sturdy shock absorber that is also a structural
component of the suspension.
• A strut is a suspension link as well as a shock absorber.

75. MacPherson Struts
• The MacPherson
strut, which is named
after Earle S.
MacPherson, who
developed the
suspension design in
the late 1940s and
patented it in 1953, is
the most commonly
used type.

76. Modified Struts
• Unlike a MacPherson unit, a modified strut does not include a
spring as part of the assembly and is used in the front on some
vehicles and on the rear of others.

77. Bump Stops
• All suspension systems have a limit of travel.
• If the vehicle hits a large bump in the road, the wheels are forced
upward toward the vehicle with tremendous force.
• Instead of allowing the metal components of the suspension to hit
the frame or body of the vehicle, a rubber or foam bumper is used
to absorb and isolate the suspension from the frame or body.
• These bumpers are called bump stops, suspension bumpers,
strike-out bumpers, or jounce bumpers. Jounce means jolt.

78. • Suspension bumpers are used on all suspension systems to
prevent metal-to-metal contact between the suspension and the
frame or body of the vehicle when the suspension “bottoms out”
over large bumps or dips in the road.