brake AUDI A6 ALLROAD 1999 C5 / 2.G Pneumatic Suspension System

6
Principles
The suspension system
As ÓsupportingÓ components of the
suspension system, the suspension elements
form the connection between the wheel
suspension and the bodywork. This system is
complemented by the spring action of the
tyres and vehicle seats.
The suspension elements include steel
springs, gas/air and rubber/elastomers or
combinations of the above.
Steel spring suspensions have become well
established in passenger vehicles. Steel
springs are available in a wide variety of
designs, of which the coil spring has become
the most widespread.
Air suspension, which has been used for
many years in heavy goods vehicles, is
Þnding increasing application in passenger
vehicles due to its system-related
advantages.
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In the case of the passenger vehicle we can
differentiate between
sprung masses
(body
with drive train and parts of the running gear)
and
unsprung masses
(the wheels, brakes
and parts of the running gear and the axle
shafts).
As a result of the suspension system, the
vehicle forms an oscillatory unit with a
natural frequency of the bodywork
determined by the sprung masses and the
matching of the suspension system (see
ÓVibrationÓ chapter).
Sprung mass
Unsprung mass Suspension element
Suspension element

7
The unsprung masses
The aim in principle is to minimise the volume
of unsprung masses and their inßuence on
the vibration characteristics (natural
frequency of the bodywork). Furthermore, a
low inertia of masses reduces the impact load
on the unsprung components and
signiÞcantly improves the response
characteristics of the suspension. These
effects result in a marked increase in driver
comfort.
Examples for the reduction of unsprung
masses:
¥ Aluminium hollow spoke wheel
¥ Running gear parts (swivel bearing, wheel
carrier, links etc.) made of aluminium
¥ Aluminium brake callipers
¥ Weight-optimised tyres
¥ Weight optimisation of running gear parts
(e.g. wheel hubs)
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See also SSP 213, chapter ÒRunning
gearÓ.
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