Service. 940.2810.47.20 Dept. I/VK-5 Changes. Part 1

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242242Service.Pneumatic suspension systemPart 1Selflevelling suspensionin the Audi A6Design and FunctionSelf-study programme 242All rights reserved, includingthe right to make technicalchanges.AUDI AGDept. I/VK-5D-85045 IngolstadtFax 0841/89-36367940.2810.47.20Technical status 11/00Printed in GermanyFor internal use only

Pneumatic self-levelling suspension systemThis self-study programme is divided into twoparts:Principles of spring suspension, damping andair suspension242 048Self-levelling suspension, A6The rear axle air suspension system for theAudi A6 Avant is described here.242 046The 4-level air suspension of the Audiallroad quattro is described in selfstudy program 243.You will find further information on theAudi allroad quattro in self-studyprogramme 241.242 0672

ContentsPagePrinciplesVehicle suspension. 4The suspension system . 6Vibration . 8Characteristic values of springs . 12Conventional running gear without self-levelling . 14Principles of air suspensionSelf-levelling air suspension .Characteristic values of air spring .Vibration damping.Shock absorbers (vibration dampers) .PDC shock absorbers .1621232533Self-levelling suspension, A6System overview . 38Air springs . 40Air supply unit. 42Diagram of pneumatic system. 43Compressor . 44Air dryer . 47Discharge valve N111 . 48Valve for suspension struts N150 and N151. 51Self-levelling suspension sender G84 . 52Self-levelling suspension control unit J197 . 54Self-levelling suspension warning lamps K134 . 55Function diagram .56Interfaces. 57The control concept . 58Other features of the control concept . 60The self-study programme will provide you withinformation on design and functions.NewNoteImportant:NoteThe self-study programme is not intended as a workshop manual.For maintenance and repairs please refer to the currenttechnical literature.3

PrinciplesVehicle suspensionWhen a vehicle travels over irregular roadsurfaces, impact forces are transmitted to thewheels. These forces pass to the bodyworkvia the suspension system and the wheelsuspension.The purpose of the vehicle suspension is toabsorb and reduce these forces.When we talk about the vehicle suspensionwe can basically distinguish between thesuspension system and the vibrationdamping system.By means of the interaction of the twosystems, the following is achieved:242 003Driving safetyDriving comfortOperating safety4Wheel contact with the road surface, whichis essential for braking and steering, ismaintained.Unpleasant and unhealthy stresses to vehiclepassengers are minimised, and damage tofragile loads is avoided.The vehicle components are protectedagainst excessive stresses.

During driving operation, the vehicle body issubject not only to the forces which cause theupward and downward motion of the vehicle,but also the movements and vibrations in thedirection of the three spatial axes.The correct matching of the springs andvibration damping system is therefore ofgreat significance.Along with the axle kinematics, the vehiclesuspension has a significant influence onthese movements and vibrations.Vertical axisLongitudinal axisTransverse axisPitchDrift242 048Tipping (roll)JerkingSwerving (yaw)Rising and sinking5

PrinciplesThe suspension systemAs ”supporting” components of thesuspension system, the suspension elementsform the connection between the wheelsuspension and the bodywork. This system iscomplemented by the spring action of thetyres and vehicle seats.In the case of the passenger vehicle we candifferentiate between sprung masses (bodywith drive train and parts of the running gear)and unsprung masses (the wheels, brakesand parts of the running gear and the axleshafts).The suspension elements include steelsprings, gas/air and rubber/elastomers orcombinations of the above.As a result of the suspension system, thevehicle forms an oscillatory unit with anatural frequency of the bodyworkdetermined by the sprung masses and thematching of the suspension system (see”Vibration” chapter).Steel spring suspensions have become wellestablished in passenger vehicles. Steelsprings are available in a wide variety ofdesigns, of which the coil spring has becomethe most widespread.Air suspension, which has been used formany years in heavy goods vehicles, isfinding increasing application in passengervehicles due to its system-relatedadvantages.Suspension elementSprung mass242 047Unsprung mass6Suspension element

The unsprung massesThe aim in principle is to minimise the volumeof unsprung masses and their influence onthe vibration characteristics (naturalfrequency of the bodywork). Furthermore, alow inertia of masses reduces the impact loadon the unsprung components andsignificantly improves the responsecharacteristics of the suspension. Theseeffects result in a marked increase in drivercomfort.Examples for the reduction of unsprungmasses: Aluminium hollow spoke wheel Running gear parts (swivel bearing, wheelcarrier, links etc.) made of aluminium213 041 Aluminium brake callipers Weight-optimised tyres Weight optimisation of running gear parts(e.g. wheel hubs)213 091See also SSP 213, chapter “Runninggear”.213 0687

PrinciplesVibrationIf a mass on a spring is deflected from its restposition by a force, a restoring force developsin the spring which allows the mass torebound. The mass oscillates beyond its restposition which results in a further restoringforce being exerted. This process is repeateduntil air resistance and the internal friction ofthe spring causes the vibration to cease.The natural frequency of the bodyworkThe vibrations are defined by the degree ofamplitude and its frequency. The naturalfrequency of the bodywork is particularlyimportant during matching of thesuspension.The natural frequency of unsprung parts isbetween 10 Hz and 16 Hz for a medium-sizevehicle. Appropriate matching of thesuspension system reduces the naturalfrequency of the bodywork (sprung mass) tobetween 1 Hz and 1.5 Hz.MassReboundVibrationRest positionCompressionAmplitudeSpring1 cycle242 0218

The natural frequency of the bodywork isessentially determined by the characteristicsof the springs (spring rate) and by the sprungmass.Greater mass or softer springs produce alower natural frequency of the bodywork anda greater spring travel (amplitude).Smaller mass or harder springs produce ahigher natural frequency of the bodywork anda lesser spring travel.Depending on personal sensitivity, a naturalfrequency of the bodywork below 1 Hz cancause nausea. Frequencies above 1.5 Hzimpair driving comfort and are experiencedas shudders above around 5Hz.DefinitionsVibrationUpward and downwardmotion of the mass(body)AmplitudeThe greatest distance ofthe vibrating mass fromthe rest position(vibration extent, springtravel)CycleDuration of a singlevibrationFrequencyNumber of vibrations(cycles) per secondNaturalfrequency ofthe bodyworkNumber of vibrations ofthe sprung mass (body)per secondResonanceThe mass is disturbed inits rhythm by a forcewhich increases theamplitude (build-up).Spring travelGreater mass or softer springsLow natural frequency of thebodyworkTime1 cycleSpring travelSmaller mass or harder springs242 072High natural frequency of thebodyworkTime1 cycle9

PrinciplesMatching of the natural frequency of thebodyworkThe degree of damping of the vibrationdamper has no significant influence on thevalue of the natural frequency of thebodywork. It influences only how quickly thevibrations cease (damping coefficient). Forfurther information, see chapter “Vibrationdamping”.The axle loads (sprung masses) of a vehiclevary, at times considerably, depending on theengine and equipment installed.To ensure that the bodywork height(appearance) and the natural frequency of thebodywork (which determines the drivingdynamics) remains practically identical for allvehicle versions, different spring and shockabsorber combinations are fitted to the frontand rear axles in accordance with the axleload.For standard running gear without selflevelling, the rear axle is alwaysmatched to a higher natural frequencyof the bodywork because when thevehicle is loaded, it is principally theload to the rear axle which increases,thus reducing the natural frequency ofthe bodywork.For instance, the natural frequency of thebodywork of the Audi A6 is matched to 1.13Hzon the front axle and 1.33Hz on the rear axle(design position).The spring rate of the springs thereforedetermines the value of the natural frequencyof the bodywork.The springs are colour-coded to differentiatebetween the different spring rates (see table).Spring rate levels of the front axle for the A6Height toleranceVehicle height242 073cF1cF 323.3cF3 3N/5.2mmcF 3N/7.2mm4N/mmcF 39.35N/mmcF 41.56N/mm 43.7N/mmNatural frequency of the bodyworkComponent tolerance bandUsable load rangeof a spring1.13 Hz800 kg10Natural frequency tolerance band850 kg900 kg950 kgAxle load

Spring allocation table (e.g. A6 front axle 1BA)PR-No. weightclass, front axleOJDStandardrunningOJEgearOJFe.g. 1 BAOJGOJHOJJOJKOJLOJMSportsrunninggeare.g. 1BEOJDOJEOJFOJGOJHOJJOJKAxle load (kg)Colour coding739 - 766767 - 794795 - 823824 - 853854 - 885886 - 918919 - 952953 - 986987 - 1023Suspension, left and right(spring rate)800 411 105 AN (29.6 N/mm)800 411 105 AP (31.4 N/mm)800 411 105 AQ (33.3 N/mm)800 411 105 AR (35.2 N/mm)800 411 105 AS (37.2 N/mm)800 411 105 AT (39.3 N/mm)800 411 105 BA (41.5 N/mm)800 411 105 BM (43.7 N/mm)800 411 105 BN (46.1 N/mm)753 - 787788 - 823824 - 860861 - 899900 - 940941 - 982983 - 1027800 411 105 P (40.1 N/mm)800 411 105 Q (43.2 N/mm)800 411 105 R (46.3 N/mm)800 411 105 S (49.5 N/mm)800 411 105 T (53.0 N/mm)800 411 105 AA (56.6 N/mm)800 411 105 AB (60.4 N/mm)1 grey, 3 violet1 green, 1 violet1 green, 2 violet1 green, 3 violet1 yellow, 1 violet1 yellow, 2 violet1 yellow, 3 violet1 violet, 3 brown1 white, 1 brown1 white, 2 brown1 white, 3 brown1 yellow, 1 brown1 yellow, 2 brown1 yellow, 3 brown1 green, 1 brown1 green, 2 brownProof of warrantyVehicle dataDate ofDeliveryVehicle identification numberType descriptionRunninggearEngine capacity / gearbox / month/year of manufactureEngine code / gearboxcode lettersPaint no. / interior equipment no.M-equipment number1BAOYF OJLWeight class offront axleUn-laden weight / consumptionfigures / CO2 emissionsStamp of theAudi deliverycentreWeight class ofthe rear axle242 10811

PrinciplesCharacteristic values ofspringsCharacteristic curve/spring rate of springsProgressive characteristiccurveLinear characteristic curveHard springWe can obtain the characteristic curve of aspring by producing a forces/travel diagram.If the spring rate remains the samethroughout the entire spring travel, the springhas a linear characteristic curve.A soft spring has a flat characteristic curvewhile a hard spring has a steep curve.Resilience FThe spring rate is the ratio between theeffective force and the spring travel. The unitof measurement for the spring rate is N/mm.It informs us whether a spring is hard or soft.00A coil spring is harder due to:242 018Spring travel s a greater wire diameterLinear characteristic curveSoft spring a smaller spring diameter a lower number of coilsaIf the spring rate becomes greater as thespring travel increases, the spring has aprogressive characteristic curve.Coil springs with a progressive characteristiccurve can be recognised as follows:bca) uneven coil pitchb) conical coil shapec) conical wire diameterd) combination of two spring elements(example, see next page)242 01912

Lower stop9Upper stop12Lower stop15Auxiliary spring insertRebound stop insert (in shock absorber)Un-laden positionDesign position(Example: Suspension strut with auxiliarypolyurethane springs).63242 0200-120-80-40Rebound in mm04080120Compression in mmParallel springingSpringAuxiliary springAdvantages of progressive characteristiccurve of spring: Better matching of the suspension systemfrom normal to full load. The natural frequency of the bodyworkremains practically constant duringloading. The suspension is not so prone to impactsin the case of significant irregularities inthe road surface. Better use of the available spring travel.13

PrinciplesConventional running gear(steel springs) without selflevellingSpring travelThe overall spring travel stot required forrunning gear without self-levelling iscomprised of the static compression sstat andthe dynamic spring travel caused by vehiclevibrations sdyn for both laden and un-ladenvehicles.When the vehicle is stationary, the vehiclebody retracts by a certain spring traveldepending upon the load. In this case, wespeak of static compression: sstat.stot sstat sdyn(un-laden) sdyn(fully laden)Steel suspensionsstat(un-laden)HVSupporting force in kn.The disadvantage of conventional runninggear without self-levelling is its reducedspring travel at full load.sstat(fully laden)10864H2HL-80 mm-40 mmdyn. rebound242 0750 40 mm 80 mmsstat(un-laden)(fully laden)(un-laden)fully ladenDesign positionUn-laden positionCharacteristic curve of springHV height when fully ladenH design position heightHL height when un-laden14dyn. compression

The static compression .Definitions:. is the starting point (zero) for the dynamicspring movements, compression travel (plus)and rebound travel (minus).The un-laden position . is the compression exerted onto the wheelswhen the vehicle is ready for the road (fueltank completely filled, spare wheel andvehicle tools present).The design position . is defined as the un-laden position plus theadditional load of three persons, eachweighing 68 kg. is dependant upon the spring rate and theload (sprung masses). results from the difference between thestatic compression when un-ladensstat(un-laden) and the static compression whenfully laden sstat(fully laden).sstat sstat(fully laden) - sstat(un-laden)In the case of a flat characteristic curve (softsprings), the difference and thereby the staticcompression between full and un-laden isvery great.In the case of a steep characteristic springcurve, this state of affairs is reversed and iscoupled with an excessive increase of thenatural frequency of the bodywork.Hard springsSoft springsFully ladenUn-laden position242 076sstat soft springssstat hard springs15

Principles of air suspensionSelf-levelling airsuspensionAir suspension is a controllable form ofvehicle suspension.With air suspension, it is simple to achieveself-levelling and it is therefore generallyintegrated into the system.The basic advantages of self-levelling are: Static compression remains the same,irrespective of vehicle loads (see overleaf).The space requirement in the wheelarches for free wheel movement kept to aminimum, which has benefits for theoverall use of available space. Ground clearance is maintained, whateverthe load. There are no track or camber changeswhen vehicle is laden. The cw value is maintained, as is the visualappearance. Less wear to ball joints due to reducedworking angle. Greater loads are possible if required. The vehicle body can be suspended moresoftly, which improves driving comfort. Full compression and rebound travel ismaintained, whatever the load. constant242 07416

With the aid of self-levelling, the vehicle(sprung masses) remains at one level (designposition) because the air spring pressure isadapted accordingly.Static compression is thus the same at alltimes thanks to the self-levelling system andneed not be accounted for when designingthe wheel clearances.sstat 0In addition to the main advantages offered byself-levelling, its realisation by means of airsuspension (Audi A6) offers anothersignificant advantage.As the air pressure in the air springs isadapted in accordance with the load, thespring rate alters proportionally to the sprungmass. The positive outcome is that the naturalfrequency of the bodywork and therebydriving comfort remain virtually constant,irrespective of the load.Supporting force in kN.Another feature of self-levelling airsuspension is that the natural frequency ofthe bodywork is kept virtually constantbetween un-laden and full-load (see chapter“Air spring characteristic values” page 21).Air suspension1086H constant4242 0772Spring travel-80 mmCharacteristic curvesof springsfully ladenDesign position Hun-laden-40 mm0dyn. rebound 40 mm 80 mmdyn. compressionsstat17

Principles of air suspensionFully supporting means:Another benefit is the principle-relatedprogressive characteristic curve of an airspring.Self-levelling systems are oftencombined with steel or gas-filled springdevices with hydraulic or pneumaticcontrol. The supporting force of thesesystems results from the sum of bothsystems. We therefore call them“partially supporting” (Audi 100/Audi A8).With fully supporting air suspension on bothaxles (Audi allroad quattro), different vehiclelevels can be set, e.g.: Normal driving position for city driving. Lowered driving position for high speedsto improve driving dynamics and airresistance.In the self-levelling suspension systemsin the Audi A6 (on the rear axle) and inthe Audi allroad quattro (rear and frontaxles) air springs are the onlysupporting suspension elements andthese systems are therefore describedas “fully supporting”. Raised driving position for travel off-roadand on poor road surfaces.You can find further details in SSP 243“4-Level air suspension in the Audi allroadquattro”.242 030242 0314Natural frequency of the bodywork43Spring rate210018102030321001020Supporting forceSupporting forceSteel springs (linear)Steel springs (linear)Air springsAir springs30

Design of the air springs:In passenger vehicles, air springs withU-bellows are used as suspension elements.These allow greater spring travel in restrictedspaces.The outer and inner surfaces are made of anelastomer material. The material is resistantto all weather influences and is largely oilresistant. The inner surface finish is designedto be particularly air-tight.The air springs consist of:The stability supports absorb the forcesproduced by the internal pressure in the airsprings. Upper housing closure U-bellows Piston (lower housing closure) Retaining ringsThe construction of the U-bellows can beseen in fig. 242 032.Coaxial arrangement of the air springsUpper housing closureRetaining ringInternal surface coatingWoven insert 1Woven insert 2External surface coatingPiston242 03219

Principles of air suspensionHigh-quality elastomer material andpolyamide cord woven inserts (stabilitysupports) provide the U-bellows with goodunrolling characteristics and a sensitiveresponse of the spring system.The necessary properties are ensured over awide temperature range between-35 C and 90 C.Metal retaining rings tension the U-bellowsbetween the upper housing closure and thepiston. The retaining rings are machinepressed by the manufacturer.Air springs must not be moved in anunpressurised condition since the airbellows cannot unroll on the piston andwould be damaged.In a vehicle in which the air springs areunpressurised, the relevant air springsmust be filled with the aid of thediagnostic tester (see WorkshopManual) before raising or lowering thevehicle (e.g. vehicle lifting platform orvehicle jack).The U-bellows unrolls onto the piston.Depending on the axle design, the air springsare either separate from the shock absorbersor combined as a suspension strut (coaxialarrangement).Air springsSeparate arrangement of the air springs242 042Piston20

Air spring parametersPiston and cylinderSupporting forceResilience/spring rateThe resilience (supporting force) F of an airspring is determined by the effective surfaceAw and the excess pressure in the airspring pi.pidWF pi x AwThe effective surface Aw is defined by theeffective diameter dw.In the case of a rigid structure, such as pistonand cylinder, the effective diametercorresponds to the piston diameter.In the case of air springs with U-bellows, theeffective diameter is determined by thelowest point of the fold.242 023U-bellowsSupporting forceAs the formula shows, the supporting force ofan air spring is in direct relation to theinternal pressure and the effective surface. Itis very easy to alter the supporting strength(resilience) statically (no movement of thebodywork) by varying the pressure in the airspring.dW242 0259 barSupporting forceThe various pressures, depending on theload, result in the relevant characteristiccurves of the springs and/or spring rates.The spring rate alters at the same rate as thebodywork weight, while the natural frequencyof the bodywork which determines thehandling characteristics remains constant.The air suspension is adapted to a naturalfrequency of the bodywork of 1.1 Hz.pi8 bar7 bar6 barladenun-laden-s 0 s242 078Spring travel21

Principles of air suspensionCharacteristic curve of springsThe progress of the characteristic curve of thespring (flat/steep inclination) is determinedby the spring volume.A large spring volume produces a flatprogression of the characteristic curve (softsprings), a small spring volume produces asteep progression of the characteristic curve(hard springs).The progression of the characteristic curve ofa spring can be influenced by the contour ofthe piston.Changing the contour of the piston alters theeffective diameter and thereby the resilience.ResultThe following options are available formatching the air springs using U-bellows:Small spring volumeSupporting weight weight of the sprung massesOwing to the functional principle, thecharacteristic curve of an air spring isprogressive (in the case of cylindricalpistons).Large spring volume( piston volume)9 bar8 bar7 bar6 bar-s 0 sSpring travel Size of the effective surface242 027 Size of spring volume Contour of the pistonSpring volumeSpring volumePiston volume22242 084242 026

Example of the contour of a piston(suspension strut in the Audi allroad quattro)U-bellowsPistonCompressed242 079Vibration dampingWithout vibration damping, the vibration ofthe masses during driving operation wouldbe increased to such an extent by repeatedroad irregularities, that bodywork vibrationwould build up increasingly and the wheelswould lose contact with the road surface.The purpose of the vibration damping systemis to eliminate vibrations (energy) as quicklyas possible via the suspension.Vibration dampers are available in differentdesigns but their basic function and purposeare the same.Hydraulic/mechanical damping has foundwidespread application in modern vehicledesign. The telescopic shock absorber is nowparticularly favoured due to its smalldimensions, minimum friction, precisedamping and simple design.For this purpose, hydraulic vibration dampers(shock absorbers) are located parallel to thesprings.23

Principles of air suspensionSprung massDirection oftravelUnsprung massUneven groundDamped vibrationUn-damped vibration242 022As previously mentioned, vibration dampinghas a fundamental effect on driving safetyand comfort.However, the requirements of driving safety(driving dynamics) and driving comfort areconflicting.Within certain limits, the following applies inprinciple: A higher rate of damping improves drivingdynamics and reduces driving comfort. A lower rate of damping lessens drivingdynamics and improves driving comfort.24The term “shock absorbers” ismisleading as it does not preciselydescribe the function.For this reason we shall use the term“vibration damper” instead.

Shock absorbers (vibrationdampers).Dual pipe gas-pressure shock absorberThe dual pipe gas-pressure shock absorberhas become established as the standarddamper.In the dual pipe gas-pressure shock absorber,the working cylinder and the housing formtwo chambers. The piston and piston rodmove inside the working chamber, which iscompletely filled with hydraulic oil. The ringshaped oil reservoir between the workingcylinder and the housing serves tocompensate volumetric changes caused bythe piston rods and temperature changes inthe hydraulic oil.Cavitation is the formation cavities andthe creation of a vacuum in a rapidliquid flow.The oil reservoir is only partially filled with oiland is under a pressure of 6 - 8 bar, whichreduces the tendency towards cavitation.Two damping valve units are used fordamping; the piston valve and the bottomvalve. These comprise a system of springwashers, coil springs and valve bodies withthrottle bores.242 080Gas fillingOil reservoirWorking cylinderDamping valve unit(piston valve)Damping valve unit(bottom valve)Damper valveNon-return valve25

Principles of air suspensionFunctionDuring compression, damping is determinedby the bottom valve and to a certain extent bythe return flow resistance of the piston.The oil displaced by the piston rod flows intothe oil reservoir. The bottom valve exerts adefined resistance against this flow, therebybraking the movement.During rebound, the piston valve alonecarries out the damping action and exerts apredetermined resistance against the oilflowing downwards.The oil required in the working chamber canflow back unhindered via the non-return valvein the bottom valve.CompressionReboundPiston valveOil reservoirDamper valveNon-return valve242 081Bottom valve26

Single pipe gas-pressure shock absorberWith the single pipe gas-pressure shockabsorber, the working chamber and the oilreservoir are located in a single cylinder.Volumetric changes caused by the piston rodand the temperature changes in the oil arecompensated by another gas chamber whichis separated from the working cylinder by adividing piston. The level of pressure in thegas chamber is approx. 25 - 30 bar and mustbe able to sustain the damping forces duringcompression.242 082The damping valves for compression andrebound are integrated into the piston.Piston with dampingvalvesDividing pistonGas chamberDamper valvesComparison of single/dual pipe gas-pressure shock absorbersValve functionDual pipe gas-pressure shockabsorberThe tendency towards cavitationis reduced by the gas pressure inthe oil reservoirSingle pipe gas-pressure shockabsorberMinimal tendency towardscavitation thanks to high gaspressure and separation of oil andgasDependant on the gas pressureduring compressionBetterCharacteristiccurvesShort dampingstrokesFrictionDesignAny, due to separate valves forcompression and reboundGoodInstallationpositionWeightApproximately verticalHigher due to seal under pressureLonger due to gas chamber in thecylinderAnyHeavierLighterLowGreater diameter27

Principles of air suspensionFunctionDuring compression, oil is forced out of thelower chamber through the discharge valveintegrated into the piston which exerts adefined resistance against the oil. The gascushion thereby compresses by the amountof the piston rod volume inserted.During rebound, oil is forced out of the upperchamber through the suction valve integratedinto the piston which exerts a definedresistance against the oil. The gas cushionthereby expands by the amount of theemerging piston rod lveGas cushionGas cushionDamper valves242 08328

Damping matchingWe can basically distinguish betweencompression and rebound in the dampingprocess.Advantage of this matching:Good response of the vehicle suspensionensures greater driving comfort.The damping force during compression isgenerally smaller than during rebound.Consequently, irregularities in the road aretransmitted to the vehicle bodywork withdiminished force. The spring absorbs theenergy which is quickly dissipated duringrebound by the more efficient action of theshock absorber.The disadvantage of this matching occurs inthe case of a quick succession of irregularitiesin the road. If the time between the individualimpacts is no longer sufficient for rebound,the suspension can “harden” significantly inextreme cases, impairing driver comfort anddriver safety.16001400Rebound12001000Damping force in N800600Compression400200242 084000,130,260,390,52 0,65 0,780,911,04Piston speed in m/s29

Principles of air suspensionThe degree of damping. (the factor which determines how quicklythe vibrations are eliminated)of the vehicle body is dependant on thedamping force of the shock absorber and thesprung masses.The degree of damping describes howmuch kinetic energy a vibration systembeen dissipated between two vibrationcycles as a result of damping.The damping coefficient is just anotherterm for degree of damping.If the damping force is unchanged, thefollowing applies:An increase of the sprung masses reduces thedegree of damping. This means that thevibrations are eliminated more slowly.Increased sprung massSpring travelA reduction of the sprung masses increasesthe degree of damping. This means that thevibrations are eliminated more rapidly.Low degree of dampingSpring trav

The 4-level air suspension of the Audi allroad quattro is described in self-study program 243. You will find further information on the Audi allroad quattro in self-study programme 241. Principles of spring suspension, damping and air suspension Self-levelling suspension, A6 The rear axle air suspension system for the Audi A6 Avant is .

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