BMW E87 Vehicle Chassis Suspension and Dynamic Dri

BMWServiceAftersalesTrainingParticipant'sManualVehicleChassis,SuspensionandDynamicDrivingSystemsE87TheinformationcontainedinthisParticipant'sManualisintendedsolelyfortheparticipantsofthisseminarrunbyBMWAftersalesTraining.RefertothelatestrelevantBMWServiceinformationforanychanges/supplementstotheTechnicalData.Informationstatus:[e-mail]©2004BMWGroupAftersalesTraining,München,Germany.ReprintsofthismanualoritspartsrequirethewrittenapprovalofBMWGroup,München.Participant'sManualVehicleChassis,SuspensionandDynamicDrivingSystemsE87FrontaxleRearaxleElectricsteeringlockSuspensionanddampingAdaptationofdynamicdrivingsystemsContentsVehicleChassis,SuspensionandDynamicDrivingSystemsE87Objectives1Models3Introduction5Systemcomponents7Serviceinformation3115ObjectivesVehicleChassis,SuspensionandDynamicDrivingSystemsE87TheUltimateDrivingMachineThisParticipant'sManualisintendedtoprovidefundamentalinformationonthesubjectsofthevehiclesuspensionandthe,inpart,known,dynamicdrivingsystems.Withitsbalancesrear-wheeldrive,theE87isalsocharacterizedbyBMW'sbrand-namestandards.ByworkingthroughthisParticipant'sManual,youwillgainfundamentalknowledgeofthefollowingareas:–E87Frontaxle–E87Rearaxle–Electricsteeringlock(ELV)–E87Suspensionanddamping–E87Adaptationofchassisandsuspensioncontrolsystems36ModelsBMWRearaxlesDevelopmentofBMWrearaxlesBMWchassisandsuspensionsystemsandthereforethesportiveanddynamiccharacteroftheindividualmodelshavelongbeenbasedonthespecialaxledesignsand,ofcourse,ontheintegraloptimumchassisandsuspensiontuning.ThefollowingtableshowsthedevelopmenthistoryofBMWrearaxles:DesignationDistinguishingfeaturesModelHA1Semi-trailingarmaxleE3,E9,E12,E21,E28,E30,E36/5,E36/7,E114HA2Screw-linkaxleE23,E24,E32,E34HA3Central-linkrearaxleZ1,E36/2,E36/3,E36/4,E36/C,E46,E83,E85DoublelateralcontrolarmaxleE26HA4ExperimentalstudyHA5DisperseddoublecontrolarmaxleE87IntegralIExperimentalstudyIntegralIIExperimentalstudyIntegralIIIE31IntegralIVSteel,spring,dampertowerE38IntegralIVAluminium,spring,dampertowerE39IntegralIVAluminium,springonbodyanddamperonaxlecarrierE39/2IntegralIVSteelaxlecarrier,aluminiumlinkandsteelwheelcarrier,springanddamperseparatedbutbothsupportedonbodyE53IntegralIVAluminiumaxlecarrierwithcastnodetechnologyandcastswingarm,springstrutshockabsorbertowerE65IntegralIVAluminiumaxlecarrierwithcastnodetechnologyandcastswingarm,springstrutshockabsorbertowerE6x57IntroductionVehicleChassis,SuspensionandDynamicDrivingSystemsE87E87ChassisandsuspensionAscanalreadybeseenfromtheillustration,thechassisandsuspensionoftheE87representanewstepforwardinthecompactclassbothatthefrontaxleaswellasattherearaxle.Thefrontaxleisdesignedasadoublepivotspringstrutaxle(MacPhersonstrut)inaluminium.ThedesignprincipleofthedoublepivotspringstrutfrontaxleoftheE87wasinstalledintheE23asearlyas1977.Atthattime,however,itwasinstalledwithrecirculatingball-and-nutsteeringbehindtheaxle.TheE87ontheotherhandfeaturesafront-positionedrackandpinionsteeringsystemaswasusedontheE39basicaxle.Thedesignofthefrontaxleinthe1SeriesisgenerallyverysimilartothatoftheE39notleastbecauseallitscomponentsaremadeofaluminium.1-E8767Therearaxlewascompletelyredesignedasafive-linkaxlefortheE87.ThepropertiesoftheE87frontandrearaxlearedescribedinthefollowing.2-E8778SystemcomponentsVehicleChassis,SuspensionandDynamicDrivingSystemsE87E87FrontaxleDoublepivotspringstrutaxleAlthoughatensionstrutversionofthedoublepivotspringstrutaxlehasbeenusedinBMWvehiclesforover25years,someoftheadvantages,specificallycomparedtothesingle-jointorpivotaxle,arelistedinthefollowing.Bothapositive(+)aswellasanegative(-)kingpinoffsetcanbeachievedbyrealizingthevirtualpivotaxle(alsoknownasspreadingaxle,steeringpivotorsteeringaxle).1-E87Frontaxle88Initially,itwasthoughtthatanegativekingpinoffsetshouldalwaysbeselected.However,whentakingintoconsiderationtheself-stabilizingeffectofanegativekingpinoffsetinconnectionwithasymmetricalbreakingforces,thispresumptionisjustifiedonlyunderuniformdecelerationconditions(inthestationaryorsteadyrange).Intheunsteadycase,i.e.atthestartofthebreakingprocedure,animplausiblesteeringwheelmovementoccursthatcouldconveytothedriverafalseimpressionofthedrivingsituation.Inaddition,drivingtestshaveshownthatastabilizingeffectisalsoachievedatasmallpositivekingpinoffset.Inviewofthemanyotherinfluencingfactorssuchasthecastorangle,momentofinertiaofthevehicle,widthofthetyrecontactsurface,etc.afundamentalexplanationofthischaracteristicisprovided.Theoverallvehiclehandlingisalsoconsiderablymoreharmoniouswiththedoublepivotspringstrutaxledesignedwithslightlypositivekingpinoffset.Likewise,realizationofthevirtualpivotaxlehasafavourableeffectonthepackagespaceforthebrakediscsandbrakecallipers.Inthecaseofthesingle-jointorpivotaxle,thewheelcontroljointislargelydeterminedbythesizeofthekingpinoffset.Sincethekingpinoffsetshouldbeassmallaspossible,thewheelcontroljointmustbelocatedasfartowardstheoutsideaspossible.Thishoweverresultsinproblemsconcerningthepackagespaceforthebrakediscandbrakecalliper.Onthedoublepivotspringstrutaxl