BMW E87 Vehicle Chassis Suspension and Dynamic Driving Systems

Participant's Manual

Vehicle Chassis, Suspension and

Dynamic Driving Systems E87

BMW E87 Vehicle Chassis Suspension and Dynamic Driving Systems

The information contained in this Participant's Manual is intended solely for the participants ofthis seminar run by BMWAftersales Training.

Refer to the latest relevant "BMW Service" information for any changes/supplements to theTechnical Data.

Information status: April 2004

conceptinfo@bmw.de

© 2004 BMW Group

Aftersales Training, München, Germany.

Reprints of this manual or its parts require the written approval of BMW Group,München.

BMW E87 Vehicle Chassis Suspension and Dynamic Driving Systems

Participant's Manual

Vehicle Chassis, Suspension andDynamic Driving Systems E87

Front axleRear axle

Electric steering lockSuspension and damping

Adaptation of dynamic driving systems

BMW E87 Vehicle Chassis Suspension and Dynamic Driving Systems

Contents

Vehicle Chassis,Suspension andDynamic DrivingSystems E87

ObjectivesModelsIntroductionSystem componentsService information

1

3

5

7

31

BMW E87 Vehicle Chassis Suspension and Dynamic Driving Systems

Objectives

Vehicle Chassis, Suspension and Dynamic DrivingSystems E87

The Ultimate Driving Machine

This Participant's Manual is intended toprovide fundamental information on the

subjectsofthevehiclesuspensionandthe,inpart, known, dynamic driving systems.With its balances rear-wheel drive, the E87 isalso characterized by BMW's brand-namestandards.

By working through this Participant's Manual,you will gain fundamental knowledge of thefollowing areas:–E87 Front axle–E87 Rear axle

–Electric steering lock (ELV)–E87 Suspension and damping

–E87 Adaptation of chassis and suspensioncontrol systems

BMW E87 Vehicle Chassis Suspension and Dynamic Driving Systems

Models

BMW Rear axles

Development of BMW rear axles

BMW chassis and suspension systems andthe integral optimum chassis and suspensiontherefore the sportive and dynamic charactertuning.

oftheindividualmodelshavelongbeenbasedonthespecialaxledesignsand,ofcourse,on

The following table shows the developmenthistory of BMW rear axles:

HA 2Screw-link axle

E23, E24, E32, E34HA 3Central-link rear axle

Z1, E36/2, E36/3,E36/4, E36/C, E46,E83, E85Double lateral control arm axleE26HA 4Experimental study

HA 5Dispersed double control arm axleE87

Integral IExperimental studyIntegral IIExperimental study

Integral IIIE31Integral IVSteel, spring, damper tower

E38Integral IVAluminium, spring, damper tower

E39Integral IVAluminium, spring on body and damper on axleE39/2

carrier

Integral IV

Steel axle carrier, aluminium link and steel wheelE53carrier, spring and damper separated but bothsupported on body

Integral IV

Aluminium axle carrier with cast node technologyE65and cast swing arm, spring strut shock absorber

BMW E87 Vehicle Chassis Suspension and Dynamic Driving Systems

Introduction

Vehicle Chassis, Suspension and Dynamic DrivingSystems E87

E87 Chassis and suspension

1 -

E87

As can already be seen from the illustration,the chassis and suspension of the E87

represent a new step forward in the compactclassbothatthefrontaxleaswellasattherearaxle. The front axle is designed as a doublepivot spring strut axle (MacPherson strut) inaluminium.

Thedesignprincipleofthedoublepivotspringstrut front axle of the E87 was installed in theE23asearlyas1977.Atthattime,however,itwas installed with recirculating ball-and-nutsteeringbehindtheaxle.TheE87ontheotherhand features a front-positioned rack andpinion steering system as was used on theE39basicaxle.Thedesignofthefrontaxleinthe 1 Series is generally very similar to that ofthe E39 not least because all its componentsare made of aluminium.

BMW E87 Vehicle Chassis Suspension and Dynamic Driving Systems

2 -

E87

Therearaxlewascompletelyredesignedasafive-linkaxlefortheE87.ThepropertiesoftheE87 front and rear axle are described in thefollowing.

BMW E87 Vehicle Chassis Suspension and Dynamic Driving Systems

System components

Vehicle Chassis, Suspension and Dynamic DrivingSystems E87

E87 Front axle

Althoughatensionstrutversionofthedoubleadvantages, specifically compared to thepivotspringstrutaxlehasbeenusedinBMWsingle-joint or pivot axle, are listed in thevehicles for over 25 years, some of the

following.

1 -

E87 Front axle

Both a positive (+) as well as a negative (-)kingpinoffsetcanbeachievedbyrealizingthevirtual "pivot axle" (also known as "spreadingaxle", "steering pivot" or "steering axle").

BMW E87 Vehicle Chassis Suspension and Dynamic Driving Systems

2 -Pivot axle/steering axle

3 -

Double pivot spring axle/determining the lower pivot point

Initially, it was thought that a negative kingpinoffset should always be selected.

However, when taking into consideration theself-stabilizing effect of a negative kingpinoffset in connection with asymmetrical

breaking forces, this presumption is justifiedonlyunderuniformdecelerationconditions(inthe stationary or steady range). In the

unsteadycase,i.e.atthestartofthebreakingprocedure, an implausible steering wheelmovement occurs that could convey to thedriver a false impression of the drivingsituation.

In addition, driving tests have shown that astabilizing effect is also achieved at a smallpositive kingpin offset.

In view of the many other influencing factorssuchasthecastorangle,momentofinertiaofthe vehicle, width of the tyre contact surface,etc. a fundamental explanation of thischaracteristic is provided.

The overall vehicle handling is also

considerably more harmonious with thedouble pivot spring strut axle designed withslightly positive kingpin offset.

Likewise, realization of the virtual "pivot axle"has a favourable effect on the package spacefor the brake discs and brake callipers.Inthecaseofthesingle-jointorpivotaxle,thewheelcontroljointislargelydeterminedbythesize of the kingpin offset. Since the kingpinoffset should be as small as possible, thewheel control joint must be located as fartowardstheoutsideaspossible.Thishoweverresults in problems concerning the packagespaceforthebrakediscandbrakecalliper.Onthe double pivot spring strut axle the positionof the control arm and tension strut with

respecttoeachotherdeterminethesizeofthekingpin offset.

The pivot points of the control arm orwishbone and tension strut at the swivel

bearingcanthereforebeselectedsuchthatnospaceproblemsareencounteredforthebrakesystem.

BMW E87 Vehicle Chassis Suspension and Dynamic Driving Systems

4 -

3Stabilizer link8Swivel bearing4Control arm

9Hydraulic mountBoth tension struts are mounted withhave, as it were, merged to form one. Thehydraulic mounts in the front axle carrier.resultingadvantageofthedoublepivotorjointIn addition, the distance of the tension strutspring strut axle is improved directional

and control arm pivot points at the swivelstability in the high speed range and a lowerbearing largely determines the vertical forcetendency to steering instability in the lowerlever arm.

sped range (insignificant for LDS).

ThegreaterthejointsofthetensionstrutandCompared to that of the control arm, the ballcontrol arm are from each other at the swiveljoint (guide joint) of the tension strut is raisedbearing, the greater the weight reset force.at the swivel bearing, thus providing effectiveanti-dive control. A further advantage of thisOn the single-joint axle, the distance isarrangement is that this tension strut mountgenerally zero as the two joints of this axle

on the axle carrier can be arranged at

BMW E87 Vehicle Chassis Suspension and Dynamic Driving Systems

approximately the same level with respect toThedoublepivotspringstrutaxleontheotherthe mounting at the swivel bearing and doeshand features a frame which additionally

not have to be lowered. This is of particularprovidessignificantstiffeningofthefrontend.

benefittoalargeoverhangangle.Inaddition,itis possible to lower the control arm mount onthe axle carrier side, thus enabling a lower rollcentre.

Thesingle-jointaxlefeaturesonlyonetypeofTechnical data

cross brace as the axle carrier.

Camber

-12’Wheel lock, outer33°29’Kingpin inclination13°56’Press-in depth37 mm

Caster angle7°2’Tyre size185/60 R 16

Caster19.5 mm

BMW E87 Vehicle Chassis Suspension and Dynamic Driving Systems

E87 Rear axle

General

Itisdesignedasamulti-linkindependentrearsuspension axle with 5 different link arms.The newly developed rear axle with the

The designation "HA 5" does not refer to thedevelopment designation "HA 5" is used forfive links but rather represents the

the first time in the E87.

consecutivedevelopmentdesignationusedat

BMW (see models).

5 -

E87 Rear axle

Thenamesoftheindividuallinksaredefinedinthe following graphic.

BMW E87 Vehicle Chassis Suspension and Dynamic Driving Systems

Components of the rear axle

2Thrust rod7Track link

3Traction strut8Semi-trailing arm

BMW E87 Vehicle Chassis Suspension and Dynamic Driving Systems

6 -

Rear axle from rear left (top) and from front left (bottom)

BMW E87 Vehicle Chassis Suspension and Dynamic Driving Systems

7 -

Top view of rear axle, left

Various links of HA 5

Thetopviewofthetwoupperlinks(blueintheillustration)formatriangleasdothetwolowerlinks (purple in the illustration).The rear link (orange in the illustration)represents the track rod.