Rear Absorber Rev1

8/13/2019 Rear Absorber Rev1

1/9

INTERNATIONAL ISLAMIC UNIVERSITY MALAYSIA

CO-CURRICULAR ACTIVITIES CENTER

CCAS 3382 - AUTOSKILL 2

:: REAR ABSORBER ::
http://images.google.com.my/imgres?imgurl=http://www.ing.unitn.it/~genelett/images/iium_logo.jpg&imgrefurl=http://www.ing.unitn.it/~genelett/conferences.htm&h=171&w=178&sz=8&tbnid=fmb2q9nEKVAJ:&tbnh=91&tbnw=95&hl=en&start=3&prev=/images%3Fq%3Diium%26svnum%3D10%26hl%3Den%26lr%3D


2/9

INTRODUCTION

Car Suspension (Rear Absorber)

-The rear absorber of a car forms part of the suspension system of the vehicle.

The suspension system of a car is essential to provide proper control of the vehicle. The function

of the suspension system is to:

- Maximize the friction between the tires and the road surface

- Provide steering ability with good handling to the vehicle

- Ensure comfort of the passengers in the car

-hen a vehicle encounters a bumpy road! the suspension system absorbs the energy of the

vertically accelerated wheel allowing the frame and the body of the vehicle to ride undisturbed

while the wheels follow the bumps on the road.

-ithout the existence of a suspension system! a bump in the road will cause the wheel to move

up and down perpendicular to the road surface. The energy in the wheel will in turn be

transferred to the frame of the vehicle and the vehicle will move up and down slamming into the

road surface. "ence! a suspension system is needed to #eep the vehicle stable.

-$ehicle dynamics is #nown as a study of the forces at wor# on a moving vehicle. The dynamics

of a moving car can be considered from two perspectives:

- %ide: this is the ability of a car to smooth out on bumpy roads

- "andling: this is the ability of a car to safely accelerate! bra#e and corner

&rom these two perspectives! a car suspension system tends to provide solutions pertaining to

road isolation! road handling! and cornering.

- %oad isolation is the ability of the vehicle to absorb or isolate road shoc# from the

passenger compartment. Therefore! it allows the vehicle to ride undisturbed while

travelling over rough roads.

- %oad handling is the degree to which a car maintains contact with the road surface in a

straight line and in various types of directional changes. To achieve this! the suspension


3/9

system #eeps the tires in contact with the ground because a vehicle's ability to steer!

bra#e and accelerate is determined by the friction between the tires and the road.

- (ornering is the vehicle's ability to travel in a curved path. The suspension achieves

improves cornering by minimizing body roll which occurs as centrifugal force pushes

outward on a car's centre of gravity while cornering! raising one side of the vehicle and

lowering the other. The suspension system therefore stabilizes the weight of the car while

cornering.

Parts of a Suspension System

The suspension system of a vehicle consists of three fundamental components which are:

springs, dampers and antis!ay bars"

1. Springs

The springs of a suspension system are based on four basic designs which are #oi$ springs, $eaf

springs, torsion bars and air springs"

- The coil spring is the most common type of spring used. )t is simply a heavy-duty torsion

bar coiled around an axis. The springs compress and expand to absorb the motion of thecar.

- The leaf spring consists of several layers of metals bound together to act as a single unit.

This #ind of spring is used on most truc#s and heavy-duty vehicles.


4/9

- Torsion bars ma#e use of the twisting properties of a steel bar to provide a coil-spring-li#e performance. This is achieved when the torsion bar twists along its axis in response

to a bump in the road thereby providing a spring force for the vehicle.

- *ir springs consist of a cylindrical chamber of air positioned between the wheel and car's

body. This #ind of springs utilizes the compressive +ualities of air to absorb wheel

vibrations.

-The position of the springs on a vehicle and the tensions in the springs determine the sprung

mass and the unsprung mass of the vehicle. The sprung mass of a vehicle is the mass of the

vehicle when it is supported on the springs while the unsprung mass is the mass between the road

and suspension springs.

-The stiffness of the springs affects how the sprung mass responds when the car is being driven.

,oosely sprung cars provide more comfort when it comes to swallowing bumps. "owever! this is

at the cost of the handling of the car because the car tends to sway during cornering and is more

prone to dive during brea#ing and acceleration.


5/9

- n the other hand! a tightly sprung car provides more handling by minimizing the body motion

of the vehicle. There are however! less tolerance in absorbing bumps! hence providing less

comfort.

2. Shock Absorber

The shoc# absorber is in a form of a damper. * damper is necessary to absorb the energy

dissipated from the spring as a result of its expansion and contraction. Thus! shoc# absorber

controls unwanted spring motion through damping. This is achieved by transforming the #inetic

energy of the spring into heat energy that can be dissipated through hydraulic fluid.

The shoc# absorber is an oil pump placed between the frame of the car and the wheels. The

upper mount of the shoc# connects to the frame of the car while the lower mount connects to the

axle near the wheel.

hen the wheel of the car encounters a bump! the spring coils and uncoils! the energy of the

spring is then transferred to the shoc# absorber through the upper mount! down through the

piston rod and into the piston. The shoc# absorber contains orifices that perforate the piston and

allow fluid to lea# through as the piston moves up and down in the pressure tube. ince the

orifices are relatively tiny! only a small amount of fluid passes through. This slows down the

movement of the piston which in turn slows downs the movement of the springs.


6/9

The shoc# absorber wor#s in two cycles! the compression cycle and the extension cycle. The

compression cycle occurs when the hydraulic fluid in the chamber below the piston is

compressed as a result of the downward movement of the piston. n the other hand! the

extension cycle occurs when the hydraulic fluid in the chamber above the piston is compressed

as a result of the piston moving upwards.

The compression cycle of the absorber controls the motion of the vehicle's unsprung weight

while the extension cycle of the absorber controls the motion of the vehicle's sprung weight.

3. Anti-sway Bars

*nti-sway bars are used together with the shoc# absorber to provide additional stability to a

moving vehicle. *n anti-sway bar consists of a metal rod that spans the entire axle and

effectively /oins each side of the suspension together. The anti-sway bar transfers movements

from one wheel to the other thereby creating a more stable and level ride. This reduces the sway

of the vehicle as it moves along corners.


7/9

C%anging and Rep$a#ement Steps for Rear Absorber

The following steps will demonstrate the process re+uired in changing the rear absorber

Step &'

0se the /ac# to lift the rear half of the vehicle off the ground. This will relieve the tension on the

wheels and suspension system. There should be enough space for a comfortable wor#ing area

beneath the vehicle.

Step '

%emove the wheels associated with the shoc#s to be replaced. 1eep the nuts and bolts in a safe

place.

Step '

0nfasten the lower attachment bolt that holds the shoc# absorber in place.

Step *'

2isconnect the shoc# absorber's upper attachment. 3et the new shoc# absorber ready for

installation.

Step +'

)nstall the rubber cushions that accompany the new set of shoc# absorber. These cushions are

designed to fit on the threaded rod.

Step '

%emove the plastic straps that are used to compress the new shoc# absorber.

Step -'

)nstall the new shoc# absorber in a reverse process in which they were removed! starting with the

upper attachment and then the lower attachment. nce the shoc# absorber is fit into its correct

position! fasten the re+uired nuts and bolts in place.


8/9

Step .'

%eplace the wheel that was removed and lower the vehicle by removing the /ac#.

Pri#e and /abor C%arge

The price and labor charges for the rear absorber vary for each different car. The price +uotations

for some of the popular cars in Malaysia are listed in the table below:

(ar Model %ear *bsorber Price 4Pair5 %eplacement (harge 4Pair5

Toyota $ios %M678.88 %M98.88

Proton 3en6 %M78.88 %M;8.88

1ancil %M lea#age of the damping fluid! seizing up

and softening are the most common failure scenarios.

*lthough shoc# absorbers typically last between 98!888#m and ?8!888#m! life spans

twice or even three times longer than this range are common. Most shoc# absorbers lose


9/9

their damping properties over time as the valve within the shoc# absorber body wears!

and the damping oil run out.

oft shoc# absorbers cause poor road handling and ride +uality. The most obvious thing

to do is to first see if there is any external damage or lea#age.

The classic method of testing is the @bounce testA on all four corners of the vehicle. &irst!

push the vehicle as far down as you can and then release. bserve the up-down motion of

the vehicle after release. )t should bounce up and down /ust once before coming to a

standstill. &urther bouncing means that the damping properties of the shoc# absorbers

have been compromised and less than one round of bouncing means that there is possible

seizure.

Documents

Rear Absorber Rev1