Automotive Suspension System

1. UNIT II
VEHICLE SUSPENSION SYSTEM
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.
Role of Suspension System
The main role of suspension system are as follows:
1. It supports the weight of vehicle.
2. Provides smoother ride for the driver and passengers i.e. act as
cushion.
3. Protects your vehicle from damage and wear.
4. It also plays a critical role in maintaining self-driving conditions.
5. It also keeps the wheels pressed firmly to the ground for traction.
6. It isolates the body from road shocks and vibrations, which would
otherwise be transferred to the passengers and load.
Principle of Suspension
Principle:-
When a tire hits an obstruction, there is a reaction force. The size of this
reaction force depends on the unsprung mass at each wheel assembly.
In general, the larger the ratio of sprung weight to unsprung weight, the less
the body and vehicle occupants are affected by bumps, dips, and other surface

2. imperfections such as small bridges. A large sprung weight to unsprung
weight ratio can also impact vehicle control.
Function Suspension System
 Supports the weight.
 Provides a smooth ride.
 Allows rapid cornering without extreme body roll.
 Keeps tires in firm contact with the road.
 Prevents excessive body squat.
 Prevents excessive body dive.
 Allows front wheels to turn side-to-side for steering.
 Works with the steering system to keep the wheels in correct
alignment.
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.
Basic suspension movements:

3. 1. Yawing (Bouncing): The vertical movement of the complete body.
2. Pitching: The rotating movement of all the parts between the spring and
road and the portion of spring weight itself.
3.Rolling: The movement about longitudinal axis produced by the centrifugal
force during cornering
Main Types of Suspension System
1. Dependent (Non Independent)
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
2. Independent
Each wheel is free to react to whatever change in surface without directly
affecting the others – most modern cars.
Advantages - Better ride & handling

4. SPRUNG MASS AND UNSPRUNG MASS
Sprung Mass :
 In a vehicle with a suspension, such as an automobile, motorcycle or a tank,
sprung mass (or sprung weight) is the portion of the vehicle's total mass
that is supported above the suspension.
 The sprung weight typically includes the body, frame, the internal
components, passengers, and cargo.
Unsprung Mass :
 In a ground vehicle with a suspension, the unsprung weight (or the
unsprung mass) is the mass of the suspension, wheels or tracks (as
applicable), and other components directly connected to them, rather than
supported by the suspension.
 Unsprung weight includes the mass of components such as the wheel
axles, wheel bearings, wheel hubs, tires, and a portion of the weight of
drive shafts, springs, shock absorbers, and suspension links.
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.

5. For best handling and ride, the unsprung weight should be kept as low as
possible.
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
TYPES OF SUSPENSION SYSTEM

6. SUSPENSION 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.
Types of springs
1) Coil spring
2) Leaf spring
3) Rubber spring
4) Air spring
5) Torsion bar
1) COIL SPRING
Spring Materials
Most springs are made of a tempered steel alloy known as spring steel,
usually chrome silicon or chrome-vanadium alloy.
Requirement Of Spring
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.
a) Coil diameter.
b) Number of coils.
c) Height of spring.
d) Diameter of the steel
coil that forms the
spring.

7. • 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.
• Springs are designed to provide desired ride and handling and come in a
variety of spring ends.
Spring Rate :
1. Spring rate, also called deflection rate, is a value that reflects how much
weight it takes to compress a spring a certain amount.
2. A constant-rate spring continues to compress at the same rate throughout
its complete range of deflection.
3. 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.
4. Before a spring is installed on a vehicle or any load is placed on it, it is at
its uncompressed length, or free length.
5. Once installed, the weight of the corner of the vehicle resting on the
spring is called its static load.
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.

8. 2) LEAF SPRINGS
• Leaf springs are formed by bending.
• They are made of long strips of steel.
• Each strip is named as Leaf.
• The long leaf is called Master Leaf, and it consists of eyes at its both ends.
• One end is fixed to the chassis frame, the other end is fixed to the shackle
spring.
• The spring will get elongated during expansion and shortened during
compression.
• This change in length of spring is compensated by the shackle.
• The U-bolt and clamps are located at the intermediate position of the
spring.
• The bronze or rubber bushes are provided on both eyes on the master leaf.
• Originally called a laminated or carriage spring

9. MATERIAL FOR LEAF SPRING
There are six types of leaf springs
1. Full – elliptic type
2. Semi – elliptic type
3. Quarter – elliptic type
4. Three Quarter – elliptic type
5. Transverse Spring type
6.Helper Spring type

10. 1. Full Elliptic
The advantage of this type is the elimination of shackle and spring
The lubrication and wear frequently, which are one of the main drawback of
this type of springs.
2. Semi – Elliptic
This type is more popular for rear suspension are used in 75% of cars.
3. Quarter – Elliptic
 This type is rarely used in now a days.
 It gives very less resistance in road shocks.

11. 4. Three Quarter – Elliptic
 This type is rarely used in now-a-days.
 It gives resistance, but occupies more space than other types.
5. Transverse Spring
 This type of spring is arrange transversely across the car instead of
longitudinal direction.
 The transverse spring for front axle, which is bolted rigidly to the frame
at the centre and attached to the axle by means of shackle at both ends.
6. Helper Spring

12.  The helper springs are used in heavy vehicles for rear suspension.
 When vehicle fully loaded the main spring as well as helper spring to
come in action and absorb the road shocks.
 When the load of the vehicle is less, the helper spring will not act and
the main spring only absorb the road shocks.
3) RUBBER SPRING
As rubber can store more energy per unit mass than any other type of spring
material, considerable weight can be saved with rubber suspension. Rubber
springs, if works on compression or shear, can be used as the main suspension
spring, otherwise can be fitted along with metal springs to improve the
suspension characteristics. Large rubber ‘bump’ stops used in many
suspension layouts stiffens the suspension spring against maximum
deflection
A rubber suspension system in a simplified form, that is similar to the one
used on a popular small car. The spring is installed between the frame and the
top link of the suspension system. When the spring is connected to a point
near the link pivot, deflection of the spring reduces to a minimum, without
affecting the total wheel movement. This arrangement of spring provides a
rising-rate characteristic, which is ‘soft’ for small wheel movements but
becomes harder as the spring deflects.
The energy released from the rubber spring after deflection is considerably
less than that imparted to it. This internal loss of energy is called hysteresis,
which is an advantage, because lower-duty dampers may be used. Some
rubber suspension systems have a tendency to ‘settle down’ or ‘creep’ during
the initial stages of service, therefore allowance for this must be provided.

13. WORKING
Types
1. Compression spring
2. Compression-shear spring
3. Steel-reinforced spring
4. Progressive spring
5. Face-shear spring
6. Torsional shear spring
Advantages

14. 1.
2.

15. 3.
4.
5.

16. 4) AIR SPRING
6.

17.  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.
 Some air springs are in effect auxiliary springs inside a coilspring 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.
Advantages
 Variable space for wheel deflection is put for optimum use for
automatic height control
 Head light alignment does not vary due to different loading condition.
 It improve the ride comfort.
 Reduce noise in suspension system.
Disadvantages
 Higher initial cost
 Occupies more space.
 Maintenance cost is more
 Due lack of friction damping is necessary due road shock
5) TORSION BAR

18.  A torsion bar is a spring which is a long, round, hardened steel bar similar
to a coil spring except for a straight bar.
 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. A torsion
bar is a solid bar of steel which is connected to the car chassis at one end,
and free to move at the other end. They can be mounted across the car or
along the car .The springing motion is provided by the metal bar's
resistance to twisting.
 To over-simplify, stick your arm out straight and get someone to twist your
wrist. Presuming that your mate doesn't snap your wrist, at a certain point,
resistance in your arm (and pain) will cause you to twist your wrist back
the other way. That is the principle of a torsion bar.
 Torsion bars are normally locked to the chassis and the suspension parts
with splined ends. This allows them to be removed, twisted round a few
splines and reinserted, which can be used to raise or lower a car, or to
compensate for the natural 'sag' of a suspension system over time. They
can be connected to just about any type of suspension system.
Advantages
 Light in weight.
 Less space occupies .
 Its maintenance cost is less.
 Initial cost is less.
 Ride comfort is more.
Disadvantages
 It does not take accelerate & Braking thrust so required additional
linkages.
 Due lack of friction damping is necessary due road shock.
Applications: - SUV Tata Safari, Tempo Trax

19. INDEPENDENT FRONT SUSPENSION SYSTEM
 To overcome disadvantages associated with the rigid-beam-axle
suspension, independent front suspension (IFS) is used. The term
independent suspension describes any system that connects the wheels to
the frame in which the movement of one wheel has no effect on the other
wheel.
 The centrifugal force is created in sprung vehicle bodies when cornering
forms a roll couple that tilts or rolls the body outwards. The body roll is
encountered by a resisting couple, produced by the product of the springs’
reaction forces and effective distance between them. Therefore, the
necessary reaction stiffness of the spring to resist the roll couple increases
or decreases as the effective distance between the springs decreases or
increases respectively. In fact the roll angle is inversely proportional to the
square of the effective spring-base width.
 The soft springs respond and deflect with the smallest road deformation
without transmitting the shocks to the vehicle body and passengers, and
hence provide better ride comfort.
• Since the independent suspension has less unsprung mass, road-wheels
follow the contour of the road irregularities up-to higher speeds than for
the heavy rigid-axle-beam suspension. As a consequence, tyre scrub and
wear are reduced with independent suspension.
• An anti-roll bar, if used in conjunction with the independent suspension,
provides the necessary resisting stiffness to oppose body roll during
cornering and hence softer springs can be employed for normal vertical
loads.
• If a separate or independent suspension for each side of the car is used, any
interaction between opposite road-wheels is reduced, so that there is less
chance of wheel wobble due to vibrational resonance.
• The engine and chassis structure can be lowered so also the centre of the
car so that the engine can be moved forward to provide more room for the
passengers.
• Independent suspension usually lowers the roll centre, hence the body rolls
before the wheels break away from the road, providing a warning to the
driver.

20. Coil spring
Strut
assembly
Frame
Shock
absorber
Control
arm
Knuckle
Disadvantages.
• The wheel cambering with body roll reduces concerning power.
• There is a slight change in wheel track, causing tyre scrub during
bouncing of one wheel.
• A more rigid chassis or sub-frame structure is required.
• A more complicated suspension and steering linkage and pivot joints
are necessary, so that the suspension becomes more expensive and
tends to wear more.
• Effects of unbalanced-wheel-assembly are transmitted to the steering-
wheel more easily and are also more pronounced.
• Steering-geometry alignment is more critical and requires more
frequent attention.
1. MacPherson Strut Suspension
Steering knuckle
Control
arm
Cradle
Frame
Strut

21. • The top of the strut is bolted to a reinforced section of the frame structure.
• The lower end of the strut is attached to a steering knuckle.
• The control arm is also attached to the steering knuckle.
• The control arms are mounted on a cradle section of the frame.
• An anti-roll bar links the two control arms together to reduce
• sway (body roll).
2. Double wishbone Suspension (SLA, A-arms)
The most common design for the front suspension of American car following
World War II used two lateral control arms to hold the wheel. The upper and
lower control arms are usually of unequal length from which the acronym
SLA (short-long arm) gets its name. These are often called “A-arms” in the
United States and “wishbones” in Britain. This layout sometimes appears
with the upper. A-arm replaced by a simple link, or the lower arm replaced
by a lateral link, the suspensions are functionally similar. The SLA is well
adapted to front-engine, rear-wheel-drive cars because of the package space
it provides for the engine oriented in the longitudinal direction. Design of the
geometry for a SLA requires careful refinement to give good performance.
The camber geometry of an unequal-arm system can improve camber at the
outside wheel by counteracting camber due to body roll, but usually carries
with it less-favourable camber at the inside wheel (equal-length parallel arms
eliminate the unfavourable condition on the inside wheel but at the loss of
camber compensation on the outside wheel). At the same time, the geometry
must be selected to minimize tread change to avoid excessive tire wear
(Gillespie 1992). The compact design of a coil spring makes it ideal for use
in front suspension systems. Two types of coil spring mountings are used. In
the first type the spring is positioned between the frame and the lower control
arm as shown in Figure 2.1. This mounting is most often used on cars with a
conventional frame or a partial front frame. The second type of mounting is
shown in Figure 2.2. In this mounting, the coil spring is positioned between
the upper control arm and a spring tower formed in the inner section of the
fender (Remling 1983). The wishbones may or may not be equal or parallel.
The wishbones are parallel and equal in length as shown in Figure 2.3.(a).
The parallel and unequal length wishbone suspension system is shown in
Figure 2.3.(b). A further refinement is the nonparallel, unequal length
wishbone suspension system illustrated in Figure 2.3.(c) (Ünlüsoy 2000).

22. Figure 2.1. A first type of independent front suspension system
(Source: Remling 1983)
Figure 2.2. A second type of independent front suspension system
(Source: Remling 1983)
(a) Parallel and equal (b) Parallel and unequal (c) Nonparallel and unequal
Figure 2.3. Double wishbone suspension designs
(Source: Ünlüsoy 2000)

23. INDEPENDENT REAR SUSPENSION
Almost all the advantages of independent front suspension apply to
independent rear suspension, but the most important among them is the
reduction of unsprung weight. The final-drive unit and the brakes contribute
maximum to the unsprung weight. Therefore, installation of ‘inboard’ brakes
on a frame-mounted final drive provides a reduction in unsprung weight of
around 50 percent. Following are the brief description of independent rear
suspension
systems.
a. Parallel Link System.
In this layout two wishbone-shaped links, which connect the wheels to a
backbone-type frame , are mounted transversely. Torsion bars are fitted
longitudinally and are connected with the lower wishbone. Wide-angle’
universal joints are used to transmit drive from the final drive.
b. Swinging Arm System.
The trailing arm system provides an alternative method of mounting the
wheels. Either a spring, shown in the figure or a torsion bar, acting at the
pivot is incorporated. One popular lighter design uses a rubber spring;
otherwise, metal spring shown in the figure is commonly used.

24. c. Swinging Half-axles.
This arrangement incorporates two axle tubes, which are jointed to the final-
drive housing so that the wheels are permitted to rise or fall (Fig. c). Universal
joints are installed at the centre of each axle joint to allow for the change in
drive angle.
Fig.c
d. Transverse Link and Coil Springs.
This layout (Fig.d) or similar is used on some models of the car. The road
wheel is positioned in the transverse plane using a tubular suspension
link at the bottom and a drive shaft at the top. Non-plunge universal joints are
used at each end of the drive shaft for movement of the shaft. A longitudinally
mounted radius arm connects the wheel end of the link to the vehicle body
and provides longitudinal stiffness and driving thrust.
Fig.d

25. e. Semi-trailing Arm and Coil Spring.
This arrangement uses a wishbone-shaped suspension arm fixed diagonally
on to a sub-frame which carries the final drive housing and also supports the
rear hub. This arrangement of the suspension arm permits the wheel to be
supported both laterally and longitudinally (Fig,e).
Fig.e.
Driving torque reaction is transferred from the final drive housing to the sub-
frame. The construction arrangement, like in similar systems, prevents the
tendency of the right-hand rear wheel to lift during hard acceleration. Braking
torque and driving thrust are taken by the suspension arms.
Rubber is commonly used at the pivots of the suspension arm and for
mounting the springs and sub-frame to the body. This provides flexibility,
reduces vibration and noise, and avoids the use of lubrication. For adjustment
of wheel alignment (toe-in), one mounting of each suspension arm is
incorporated with either eccentric adjusters or shims.
f. Transverse Link and Strut.
This layout (Fig.f) for independently mounting each rear wheel is similar to
the basic construction of the MacPherson independent front suspension
systems. The stub axle is rigidly fixed to a long vertical strut that incorporates
the suspension damper. A transverse link, in the form of a wishbone or arm,
controls the wheel track. A longitudinal tie bar links the lower end of the strut
with car body to provide a stable three-point mounting for the suspension.
This tie bar also resists the rearward movement of the road wheel. The helical
spring can be mounted either on the transverse wishbone or around the strut
in true MacPherson style.
To improve comfort, some systems use a spring having coils of differing
radius to provide a variable rate. During compression of this spring, the larger
diameter end-coils close up so that the effective working length of the spring

26. decreases, thereby stiffening the suspension. In this system, like many of
other independent rear suspension systems, the camber angle changes as
the wheel is deflected. This feature helps to alter the tyre’s cornering power,
thereby excellent handling characteristics of the car can be obtained through
proper.
Fig.f
Rubber is used at all mounting points, so slight deflection of the suspension
layout causes a change in wheel alignment. To compensate this change, it is
customary to set the rear wheels with a small amount of toe-in. It is important
to replace all washers and spacers, if removed, on non-adjustable layouts.
Other layouts often incorporate an eccentric bolt on one of the track control
arms.

27. HYDRAULIC OR HYDRO-ELASTIC SUSPENSION:
• The main component of the hydraulic suspension is the displacer unit,
which is attached to the individual wheels of the vehicle.
• The displacer unit consists of two chambers.Chamber A is just above the
flexible diaphragm and the other B is above the separating member and
connected by the other displacers by a hose pipe.
• The stem is usually connected to the lower link of the double
wishbone.
• The diaphragm is connected with the piston and bears the wheel load.
• The fluid in chamber A can all the time pass into the chamber B through
the bleed holes provided in the separating member.
• When the pressure of liquid in B rises sufficiently above that in A, then the
rubber flap valve which is loaded by the spring will open downwards thus
allowing the fluid to pass from B to A through the holes.
• Similarly, to pass the fluid from A to B the damper valve functions
accordingly.
• The fluid in B acts on the under side of the rubber element and through the
hose pipe is transmitted to the other wheel unit.

28. • The Canister Displacer unit in Hydraulic suspension is provided at the
outside of the rubber element, while the pot member at inside.
• The canister is fixed to the body structure of the vehicle.
ROLL CENTER
Fig. 1: Roll Center
• The roll center of a vehicle is the notional point at which the cornering
forces in the suspension are reacted to the vehicle body.There are two
definitions of roll center. The most commonly used is the geometric (or

29. kinematic) roll center; the Society of Automotive Engineers uses a force-
based definition.
• The location of the geometric roll center is solely dictated by
the suspension geometry, and can be found using principles of the instant
center of rotation. The SAE's definition of the force based roll center is,
"The point in the transverse vertical plane through any pair of wheel
centers at which lateral forces may be applied to the sprung mass without
producing suspension roll".
• The lateral location of the roll center is typically at the center-line of the
vehicle when the suspension on the left and right sides of the car are mirror
images of each other.
• The significance of the roll center can only be appreciated when the
vehicle's center of mass is also considered. If there is a difference between
the position of the center of mass and the roll center a moment arm is
created. When the vehicle experiences angular velocity due to cornering,
the size of the moment arm, combined with the stiffness of the springs
and anti-roll bars (anti-sway bars in some parts of the world), dictates how
much the vehicle will roll. This has other effects too, such as dynamic load
transfer.
ANTI-ROLL BAR (ROLL BAR, ANTI-SWAY BAR, SWAY
BAR, STABILIZER BAR)

30. • An anti-roll bar anti-roll bar (roll bar, anti-sway bar, sway
bar, stabilizer bar) is a part of many automobile suspensions that helps
reduce the body roll of a vehicle during fast cornering or over road
irregularities. It connects opposite (left/right) wheels together through
short lever arms linked by a torsion spring.
• A sway bar increases the suspension's roll stiffness—its resistance to roll
in turns, independent of its spring rate in the vertical direction.
• An anti-sway or anti-roll bar is intended to force each side of the vehicle
to lower, or rise, to similar heights, to reduce the sideways tilting (roll) of
the vehicle on curves, sharp corners, or large bumps. With the bar removed,
a vehicle's wheels can tilt away by much larger distances
• A sway bar is usually a torsion spring that resists body roll motions. It is
usually constructed out of a cylindrical steel bar, formed into a "U" shape,
that connects to the body at two points, and at the left and right sides of the
suspension. If the left and right wheels move together, the bar rotates about
its mounting points. If the wheels move relative to each other, the bar is
subjected to torsion and forced to twist. Each end of the bar is connected
to an end link through a flexible joint. The sway bar end link connects in
turn to a spot near a wheel or axle, transferring forces from a heavily loaded
axle to the opposite side.
• Forces are therefore transferred:
from the heavily loaded axle
1. to the connected end link via a bushing
2. to the anti-sway (torsion) bar via a flexible joint
3. to the connected end link on the opposite side of the vehicle
4. to the opposite axle.
• The bar resists the torsion through its stiffness. The stiffness of an anti-roll
bar is proportional to the stiffness of the material, the fourth power of its
radius, and the inverse of the length of the lever arms (i.e., the shorter the
lever arm, the stiffer the bar). Stiffness is also related to the geometry of
the mounting points and the rigidity of the bar's mounting points. The
stiffer the bar, the more force required to move the left and right wheels
relative to each other. This increases the amount of force required to make
the body roll.
• In a turn the sprung mass of the vehicle's body produces a lateral force at
the centre of gravity (CG), proportional to lateral acceleration. Because the
CG is usually not on the roll axis, the lateral force creates a moment about
the roll axis that tends to roll the body. (The roll axis is a line that joins the
front and rear roll centers). The moment is called the roll couple.

31. • Roll couple is resisted by the suspension roll stiffness, which is a function
of the spring rate of the vehicle's springs and of the anti-roll bars, if any.
The use of anti-roll bars allows designers to reduce roll without making the
suspension's springs stiffer in the vertical plane, which allows improved
body control with less compromise of ride quality.
Functions
Anti-roll bars provide two main functions.
1. The first function is the reduction of body lean. The reduction of body lean
is dependent on the total roll stiffness of the vehicle. Increasing the total roll
stiffness of a vehicle does not change the steady state total load (weight)
transfer from the inside wheels to the outside wheels, it only reduces body
lean. The total lateral load transfer is determined by the CG height and track
width.
2. The other function of anti-roll bars is to tune the handling balance of a
car. Understeer or oversteer behavior can be tuned out by changing the
proportion of the total roll stiffness that comes from the front and rear axles.
Increasing the proportion of roll stiffness at the front increases the proportion
of the total load transfer that the front axle reacts to—and decreases the
proportion that the rear axle reacts to. In general, this makes the outer front
wheel run at a comparatively higher slip angle, and the outer rear wheel to
run at a comparatively lower slip angle, which is an understeer effect.
Increasing the proportion of roll stiffness at the rear axle has the opposite
effect and decreases understeer.
Drawbacks
1. Because an anti-roll bar connects wheels on opposite sides of the vehicle,
the bar transmits the force of a bump on one wheel to the opposite wheel. On
rough or broken pavement, anti-roll bars can produce jarring, side-to-side
body motions (a "waddling" sensation), which increase in severity with the
diameter and stiffness of the sway bars. Other suspension techniques can
delay or dampen this effect of the connecting bar.
2. Excessive roll stiffness, typically achieved by configuring an anti-roll bar
too aggressively, can make the inside wheels lift off the ground during hard
cornering. This can be used to advantage: many front wheel drive production
cars lift a rear wheel when cornering hard in order to overload the opposite
wheel, limiting understeer.

32. SHOCK ABSORBERS
Principle :
A shock absorber (in reality, a shock "damper") is a mechanical
or hydraulic device designed to absorb and damp shock impulses. It
does this by converting the kinetic energy of the shock into another form
of energy (typically heat) which is then dissipated. Most shock absorbers
are a form of dashpot (a damper which resists motion via viscous
friction).
• Limits spring compression extension movements to smooth the vehicle’s
ride. Without shock absorbers, the vehicle would continue to bounce up
and down long after striking dip or hump in the road.
• A shock absorber is a mechanical device designed to smooth out or damp
shock impulse, and dissipate kinetic energy.

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