The Phaeton Chassis Design and Function

The Phaeton ChassisDesign and Function

Self-Study ProgramCourse Number 893303

Volkswagen of America, Inc.Service TrainingPrinted in U.S.A.Printed 08/2003Course Number 893303

©2003 Volkswagen of America, Inc.

All rights reserved. All information containedin this manual is based on the latestinformation available at the time of printingand is subject to the copyright and otherintellectual property rights of Volkswagen ofAmerica, Inc., its affiliated companies and itslicensors. All rights are reserved to makechanges at any time without notice. No partof this document may be reproduced,stored in a retrieval system, or transmittedin any form or by any means, electronic,mechanical, photocopying, recording orotherwise, nor may these materials bemodified or reposted to other sites withoutthe prior expressed written permission ofthe publisher.

All requests for permission to copy andredistribute information should be referredto Volkswagen of America, Inc.

Always check Technical Bulletins and theVolkswagen Worldwide Repair InformationSystem for information that may supersedeany information included in this booklet.

Trademarks: All brand names and productnames used in this manual are trade names,service marks, trademarks, or registeredtrademarks; and are the property of theirrespective owners.

i

Table of Contents

The Self-Study Program provides you with informationregarding designs and functions.

The Self-Study Program is not a Repair Manual.

For maintenance and repair work, always refer to thecurrent technical literature.

Important/Note!

New!

Introduction ............................................................................... 1

The Chassis

Front Axle ..................................................................................4

Front Axle

Rear Axle ..................................................................................10

Rear Axle for Front-Wheel Drive, Rear Axle for 4Motion

Alignment ................................................................................14

Measurement Guidelines

Steering....................................................................................16

Steering System Overview, Steering Column,Servotronic II Variable Effort Power Steering

Brakes.......................................................................................30

Brake System Overview, Wheel Brakes,Foot Parking Brake, Brake Lines and Cables,Pedal Cluster, Bosch 5.7 Antilock Brake System

Wheels and Tires ..................................................................... 46

Tire Pressure Monitoring

Knowledge Assessment .........................................................57

Introduction

1

In top form, the Phaeton chassis fulfillseven the most challenging demands oncomfort and driving dynamics.

The Phaeton makes important contributionsto active vehicle safety through several ofits chassis components, including:

• Speed-dependent power-assistedsteering.

• Four-link front suspension.

• Trapezoidal wishbone rear suspension.

• Electronic Stabilization Program (ESP)with Brake Assist.

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Introduction

2

The Chassis

Major chassis components and features onthe new Phaeton include:

• Four-link front suspension with64.09-inch (1628 mm) track width

• Trapezoidal wishbone rear suspensionwith 63.46-inch (1612 mm) track width

• Front and rear anti-roll bars

• Independent wheel suspension frontand rear

• Air suspension with continuouslycontrolled damping

• Foot-actuated parking brake

• Brake Assist

• Speed-dependent power-assisted steering

• Ventilated disc brakes

• Tire pressure monitor

• Electronic StabilizationProgram (ESP)

Introduction

3

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4

Front Axle

Front Axle

The Phaeton front axle is equippedwith four-link suspension. The multitudeof guide elements produces thefollowing advantages:

• Isolation from unwanted drive forcesfrom the steering.

• High steering precision throughoptimized positioning of the pivot axis.

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• Good driving comfort.

• Exceptional anti-squat and anti-diveperformance.

5

Front Axle

Component Overview

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Front and Rear UpperSuspension Links(Forged Aluminum)

Subframe(Hydroformed Steel)

Anti-Roll Bar(Steel)

Bearing Link(Forged Steel)

Guide Link(Forged Aluminum)

Wheel BearingHousing(Cast Steel)

Bearing Block(Cast Aluminum)

6

Bolted Wheel Bearings

The wheel bearings are not pressed intothe wheel bearing housings. They arebolted to the wheel bearing housing.

This enables the wheel bearing to beinstalled without removing the pivot bearingor jointed shaft.

Front Axle

Wheel Hub

Rubber Bushing withAluminum Pipe Clamps

Anti-Roll Bar

Depending on the engine, the Phaeton haseither a solid anti-roll bar 1.38 inches(35 mm) in diameter or a tubular anti-roll bar1.38 inches (35 mm) in diameter with a wallthickness of 0.24 inch (6 mm).

The rubber bushings and aluminum pipeclamps are vulcanized onto the anti-roll barin this design and cannot be replaced.

This support arrangement was designedto have radially rigid and rotationallyflexible characteristics.

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SSP277/044

WheelBearing

BoltedConnection

BoltedConnection

Wheel BearingHousing

7

Subframe

The subframe is made of high-pressurehydroformed tubular steel. It is bolted tothe body using rubber-metal bushings.This flexible connection keeps the bodyfree of forces and impacts that thechassis introduces.

The additional bolted brace ensures ampletransverse rigidity.

Front Axle

Brace

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Air Spring Strut to

Suspension Link Connection

The air spring strut is attached to thebearing link with a rubber-metal bushing. Air Spring Strut

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Bearing Link

8

Front Axle

Virtual Steering Axis

With the Phaeton four-link frontsuspension, the steering axis does not runthrough the upper and lower joints on thewheel bearing housing as with conventionalfront axle designs.

On the Phaeton front axle, the steering axisruns through two intersection points thatare derived by extending the lines formedby the two axes of the connectionsbetween the two upper suspension linkjoints, and similarly derived from theconnections between the two lowersuspension link joints.

The steering axis thus formed by the linethrough these two points of intersection isin free space. This is why it is referred to asa virtual steering axis.

It does not change position at fullsteering lock.

This arrangement enables the steering axisto be placed close to the wheel centerplane. This has a positive effect on thescrub radius which improves handling.

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2

4

1

3

R

a

p

ASA

n

nv

1-4 Directions of theSuspension Links

R Wheel Center PointA Wheel Contact Pointn Trailnv Castor Offsetp Scrub Radiusa Road Feedback Lever

ArmPoint AS = Piercing Point of

the Steering Axis onthe Road Surface

9

Front Axle

Full Steering Lock Positions

This axle design allows the virtual steeringaxes to be shifted much further outboardthan would otherwise be possible.

The position of the steering axisdetermines the castor angle and thesteering swivel inclination.

By optimizing the axle geometry, it ispossible to reduce the effects of torquesteer.

Since the wheels are located using four ballsockets on the ends of the transverse links,the pivot axis can run approximatelythrough the vertical center of each wheel,regardless of physical space requirements.

The wheel moves around the virtualsteering axis.

The virtual steering axis changes positionas the steering mechanism moves thewheels from lock to lock.

The defined movement of the virtualsteering axis during steering reduces thespace requirements in comparison toconventional axle systems with fixed-spacesteering axes.

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Link Position for Left Turn

Link Position for Right Turn

Link Position for Straight Driving

10

Rear Axle

Rear Axle for Front-Wheel Drive(Not Available in the

North American Market)

In the Phaeton, the rear axle is designedwith unequal length trapezoidal wishbonesuspension. All wheel location elementsare mounted to a rigid subframe that resiststorsion and warping.

Rear Wheel Hub

Instead of the bolted constant velocity jointpivot, the wheel bearing is pre-stressedwith a stub axle.

The rear axle for front wheel drive vehiclesis similar to the axle for all-wheel drivevehicles, but the rear axle drive and jointedshafts are not used.

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BoltedConnection

Stub Axle

BoltedConnection

WheelBearingHousing

Wheel Hub

The subframe is connected to the bodyusing large dimension rubber bushings.This configuration achieves exact wheellocation and good ride quality.

11

Rear Axle

Rear Axle for 4Motion

All Phaetons sold in the North Americanmarket have 4Motion all-wheel-drivesystems. The subframe holds the reardifferential at three points.

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Between the isolation provided at thesethree mounting points, and the isolationprovided by the subframe mounts, the reardifferential is doubly isolated from the body.

12

Integrating a coupler into the hub carrierconnection and using a track rod hasoptimized the toe-in behavior of therear axle.

Rear Axle

The passive steering properties andnoise insulation provided by the Phaetonrear axle design have improved upondesigns used in previous vehicles.

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WheelBearingHousing Coupler Track Rod

Bolted Joint forTrack Correction

Bolted Joint forCamber Correction

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Rubber-MetalBushing

Cast AluminumAxle Link

Forged AluminumTransverse Link

Steel Subframe

13

Anti-Roll Bar

An solid anti-roll bar 0.79 inch (20 mm) indiameter is installed on the rear axle.

The rubber bushings are vulcanized ontothe rear axle anti-roll bar as they are on thefront axle anti-roll bar.

Rear Axle

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Rubber Bushings

Wheel Bearing Housing

As with the front axle wheel bearings, therear axle wheel bearings are bolted to thewheel bearing housings.

The wheel bearings on the front and rearaxles are identical in construction.

Bolted Connection

Bolted Connection

Wheel BearingHousing

Wheel Hub

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14

Alignment

Measurement Guidelines

Before every alignment measurement, thelevel position of each suspension strutmust be checked.

The familiar parameters of camber andtoe-in must be measured and adjusted asnecessary on the rear or front axle duringalignment procedures.

In addition, toe-in must be checked andset as necessary at the front axle when thesuspension is extended. This adjustmentmust be made with the wheels raised2.36 inches (60 mm) when the vehicleis empty.

Adjusting the toe-in curve with the wheelsin an extended state sets the toe-in curvefor driving stability.

60 40 20 -20 -40 -60

-4.72 (-120)

-0.79 (-20)

-1.57 (-40)

-2.36 (-60)

-3.15 (-80)

-3.94 (-100)

0.79 (20)

3.94 (100)

3.15 (80)

2.36 (60)

1.57 (40)

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Compression

in Inches (mm)

Toe-In in Degrees

Extension

in Inches (mm)

Toe-In Curve Diagram

15

Alignment

Front-End Alignment

The following steps are important whenperforming the front-end alignment:

• Setting the basic toe-in with an emptyvehicle by changing the length of thetrack rod.

• Setting the inclination of the toe-in curveby changing the height of the outer trackrod joint.

AdjustmentRange for theToe-In Curve

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Adjustment Option for Independent Toe-In

For complete front-endalignment instructions,refer to the Repair Manual.

16

Steering

Steering System Overview

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Steering Column

The Phaeton is equipped with an adjustablesteering column.

The adjustment range is 1.97 inches(50 mm) in the axial direction and1.57 inches (40 mm) in the vertical direction.

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Steering

Electric Steering Column Adjustment

The electric steering column is steplesslyadjustable in the axial and vertical directions.

The adjustments are driven by twoelectric motors:

• Motor for Steering Column Adjustment,Vertical V123

• Motor for Steering Column Adjustment,Axial V124

17

SSP277/081

Motor forSteering ColumnAdjustment,Axial V124

CrashCarriage

Motor forSteering ColumnAdjustment,Vertical V123

Pull Tab

Console

18

Steering

Electric Steering Column

Adjustment Functional Diagram

The convenience CAN data bus carries thecommand signal to adjust the steeringcolumn, and the Driver’s Seat/MirrorPosition Control Module J543 processes it.

The Steering Column Electronic SystemsControl Module J527 interprets and readsthe driver’s input from the Steering ColumnAdjustment Switch E167 and places thesignal on the convenience CAN data bus.

The Driver’s Seat/Mirror Position ControlModule J543 then sets the Motor forSteering Column Adjustment, Vertical V123and the Motor for Steering ColumnAdjustment, Axial V124 to thecorresponding positions.

Hall-effect sensors in the Motor forSteering Column Adjustment, Vertical V123and the Motor for Steering ColumnAdjustment, Axial V124 send the returnsignals to the Driver’s Seat/Mirror PositionControl Module J543.

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Motor forSteering ColumnAdjustment,Vertical V123

Motor forSteering ColumnAdjustment,Axial V124

Control Unit forDriver Seat/MirrorPosition J543

Control Unit forSteering ColumnElectronics J527

Steering ColumnAdjustment Switch E167 ± Axial, ± Vertical

Steering ColumnVertical Position Sensor

Steering ColumnAxial Position Sensor

M

19

Steering

Electric Steering Column Lock

The Phaeton uses an electric steeringcolumn lock instead of a mechanicalsteering lock.

The electric steering column lock is anintegrated system with an electricalinterface to the Access/Start ControlModule J518 and a mechanical interface tothe steering column.

When the electric motor of the SteeringColumn Lock Actuator N360 is activated,the worm gear moves the push rod in thelongitudinal direction. To lock the steeringcolumn (terminal 15, off), the locking collarwith internal teeth is pushed over theconical locking star with external teeth untilit stops. To unlock the steering column(terminal S, on), the locking collar is pulledaway from the locking star.

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Access/StartControl ModuleJ518

Control Modulewith Two HallSensors

Steering ColumnLock Actuator N360

Push Rod

Lock

Worm Gear

Unlock

Locking StarLocking Collar

20

Steering

Servotronic II Variable EffortPower Steering

The Phaeton is equipped with Servotronic IIvariable effort power steering. This hydraulicsteering system, which is electronicallycontrolled and speed dependent, is

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distinguished by light, comfortable steeringduring parking and other low-speedmaneuvers, and a precise driving feel asspeed increases.

ServotronicSolenoidValve N119

Power SteeringPump V119

21

Steering

Servotronic Characteristic

Curve Diagram

The diagram shows how the pressurechanges with respect to steering wheelmovement in relation to driving speed.The characteristic curve has beenspecifically adjusted to the vehicle character.

Steering Wheel Movement – lbs-ft (Nm)

Pressure

0

290 (2,000)

580 (4,000)

870 (6,000)

1,160 (8,000)

1,450 (10,000)

1,740 (12,000)

psi (kPa)

0 mph(0 km/h)

31 mph(50 km/h)

75 mph(120 km/h)

7.38(10)

5.90(8)

4.43(6)

2.95(4)

1.48(2)

0 1.48(2)

2.95(4)

4.43(6)

5.90(8)

7.38(10)

The Servotronic variable effort powersteering system is based on hydraulicsteering. The hydraulic steering modifiedrotary valve uses the principle of directhydraulic reaction (feedback).

Using an electro-hydraulic converter andsteering valve enables the Servotronicsystem to change the amount of steeringassist according to driving speed.

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22

Steering

Electric Control

The Servotronic Control Module J236evaluates the road speed signal from theInstrument Cluster Combination ProcessorJ218 and converts the signal intomodulated current. This actuates theServotronic Solenoid Valve N119.

The Servotronic Solenoid Valve N119determines the hydraulic reaction at therotary valve and thus the applicationmoment at the steering wheel.

The speed-dependent influence on thesteering translates into minimum forcesrequired for steering effort at standstill andlow speeds.

Since the hydraulic reaction changes inrelation to driving speed, the applicationforce at the steering wheel increases withincreasing speed. This gives the driverespecially good road feel and precisesteering control.

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Instrument ClusterCombination Processor J218

ServotronicControl ModuleJ236

3115

Road Speed Signal

23

Safety with the Servotronic System

The steering system remains functional ifthe vehicle electrical system fails or otherelectrical faults occur. The Servotronicsystem then works using the mechanicalforced opening of the Servotronic SolenoidValve N119 at maximum hydraulic reaction.

Steering

If the road speed signal fails while driving,the Servotronic system remains at thelast given control range until the ignitionis turned off. The next time the engineis started, the maximum hydraulicreaction develops.

24

Steering

The Servotronic System in Operation

The rotary valve in neutral position –

vehicle stationary

Power Steering Pump V119 generatesthe hydraulic pressure that the Servotronicsystem requires, about 1,885 psi(13,000 kPa), which is transferred tothe rotary valve.

In the valve unit, a torsion bar is pinned tothe rotary valve on one side and to thedriving pinion and control bushing on theother side. The torsion bar is responsiblefor centering (neutral position).

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ControlBushing

RightWorkingCylinder

LeftWorkingCylinder

Pressureand FlowReliefValve

From Pump

PowerSteeringPumpV119

Reservoir

ServotronicSolenoidValve N119 Rotary Valve

ReactionPiston

Pin Connection

TorsionBar

Road Speed SignalServotronicControl Module J236

To LeftWorkingCylinder

To RightWorkingCylinder

ControlBushing

Return

Torsion Bar

RotaryValve

25

The oil that the Power Steering Pump V119supplies flows through the connection holein the valve region and into the inflow radialchannel. It then flows into the cross holesin the control bushing to the inflow controlchannels in the rotary valve.

In the valve neutral position, the oil flowsvia the open inflow control vanes into allaxial channels in the control bushing. Fromthere it also flows via the open returncontrol vanes into the return controlchannels in the rotary valve.

Steering

From these channels, the oil can flowthrough connections into the returnchamber, and from there back to theoil reservoir.

At the same time, the radial channels inthe valve body and the associated tubelines connect the right and left workingcylinder chambers.

Return

From Pump

Reaction Chamber

Reaction Piston

Control Bushing

Left Working Cylinder

Right Working Cylinder

Return Chamber

Radial Channel

Inflow Radial Channel

Radial Channel

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Axial Channel

Inflow Control Vane


Return Control Vane

Inflow Control Channel

Return Control Channel

Inflow Control Vane

Return Control Vane

26

Steering

Rotary valve in working position, left full

steering lock – driving at low speed

At left full steering lock, oil must flow to theright side of the working cylinder to assistthe steering effort.

The force at the steering wheel turns thetorsion bar in its elastic range, since it ispinned to the rotary valve at the top and tothe control bushing and driving pinion atthe bottom.

The torsion bar, which narrows in theappropriate region, turns the rotary valveagainst the control bushing.

The pressurized oil travels via the inflowcontrol vanes, which are further open,into the associated axial channels, throughthe hole in the radial channel and via a tubeline to the right cylinder chamber, thushydraulically assisting the steering rackto move.

The pressurized oil in the right cylinderchamber pushes the oil out of the leftcylinder chamber into the return line.

If the driver releases the steering wheel,the torsion bar ensures that the rotary valveand the control bushing spring back into theneutral position.

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ControlBushing


LeftWorkingCylinder


From Pump


Reservoir

ServotronicSolenoidValve N119 Rotary Valve

ReactionPiston Pin Connection

TorsionBar

Road Speed SignalServotronicControl Module J236

From LeftWorkingCylinder


ControlBushing

Return

TorsionBar

RotaryValve

27

Steering

The Servotronic Control Module J236evaluates the road speed signal and passesit on to the Servotronic Solenoid ValveN119 as modulated control current.

Due to the maximum current produced inthis driving situation, the ServotronicSolenoid Valve N119 closes and preventsoil from flowing from the inflow radialchannel to the reaction chamber.

A baffle ensures that the return pressurelevel also acts in the reaction chamber.Thus, the Servotronic rotary valve behavesas a normal rotary valve in this situation.

The steering is light and can be operatedwith little effort since the reaction hasbeen eliminated.

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Return

From Pump

Reaction Chamber

Reaction Piston

ControlBushing

From LeftWorkingCylinder


Return Chamber

Radial Channel



Radial Channel

Baffle

28

Steering

Rotary valve in working position, right

full steering lock – driving at high speed

At right full steering lock, oil must flow tothe left side of the working cylinder toassist the steering effort.

The force at the steering wheel turns thetorsion bar in its elastic range, since it ispinned to the rotary valve at the top and tothe control bushing and driving pinion atthe bottom.

The torsion bar, which narrows in theappropriate region, turns the rotary valveagainst the control bushing.

The pressurized oil travels via the inflowcontrol vanes, which are further open, intothe associated axial channels, through thehole in the radial channel and via a tube lineto the left cylinder chamber, thushydraulically assisting the steering rackto move.

The pressurized oil in the left cylinderchamber pushes the oil out of the rightcylinder chamber into the return line. If thedriver releases the steering wheel, thetorsion bar ensures that the rotary valveand the control bushing spring back into theneutral position.

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ControlBushing


LeftWorkingCylinder


From Pump


Reservoir


Rotary Valve

ReactionPiston Pin Connection

Torsion Bar

RoadSpeedSignal

ServotronicControl Module J236

To LeftWorkingCylinder

From RightWorkingCylinder

ControlBushing

Return

TorsionBar

RotaryValve

29

Steering

As the speed increases, the ServotronicControl Module J236 reduces the controlcurrent to the Servotronic Solenoid ValveN119. With this, the Servotronic SolenoidValve N119 takes on a certain openingposition and enables a limited oil inflowfrom the inflow radial channel into thereaction chamber. A baffle prevents largeamounts of oil from flowing out into thereturn chamber, so that higher pressuredevelops in the reaction chamber. Theincreased pressure acting on the reactionpiston then generates a greater pressingforce on the balls guided by V-ways. Theseballs are located between the reactionpiston and the centering piece, which isfirmly joined to the control bushing.

During straight driving, this has a positiveeffect on the centering of the rotary valve,making it particularly exact. When therotary valve pivots, the balls, which are nowmore highly loaded, exert additionalresistance against turning of the rotaryvalve. Therefore, with the hydraulic reaction

in this sequence of operations, thespecifically determined application momentrequired to move the steering wheel ishigher.

At high driving speeds, the ServotronicSolenoid Valve N119 is completely opendue to the very low or zero control current.Thus, the inflow radial channel suppliesmaximum pressure to the reaction system.When the driver turns the steering wheel tothe right, the reaction pressure alsoincreases corresponding to the prevailingoperating pressure and pushes the reactionpiston out of the reaction chamber.

As soon as the reaction pressure, which isdetermined specifically for the vehicle, isreached, the cut-off valve opens and the oilflows out into the return chamber so thatthe pressure does not increase further. Theapplication moment at the steering wheelnow does not increase further, and conveysa secure driving feel through optimumcontact with the roadway.

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Return Chamber

Centering Piece

Reaction Piston

Ball

Control Bushing

Reaction Chamber

Cut-Off Valve



Baffle

30

Brakes

Brake System Overview

The Bosch 5.7 Antilock Brake System(ABS) with integrated ElectronicStabilization Program (ESP) and hydraulicBrake Assist is standard equipment on allPhaeton models.

It is a diagonally separatedtwo-circuit system.

This high-performance brake systemincludes newly developed front andrear wheel brakes with largeventilated brake discs.

Front Wheel Brake

Pedal Cluster

Dual Brake Booster

ABS Hydraulic Unit N55

31

Brakes

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Brake Cables

Brake Lines

Rear Wheel Brake

Foot Parking Brake

32

Wheel Brakes

To satisfy demanding safety requirementsand guarantee a high level of comfort, thewheel brakes have been specially designedfor the Phaeton.

Brake Disc Sizes

The Phaeton is equipped with different sizebrake discs depending upon which engineis used on the vehicle.

Front Wheel Brakes

A new aluminum brake caliper wasdeveloped for the Phaeton frontwheel brakes.

This lightweight brake caliper consists ofa monoblock housing design that doesnot separate. It has eight pistons and fourbrake pads.

This arrangement ensures optimumconditions for pressing the brake padsonto the brake disc.

The brake caliper design has a wide reacharound the friction ring. It achieves low masscombined with optimal caliper stiffness.

Brakes

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33

Brakes

Front Brake Discs

The front brake discs are constructed fromtwo parts. A friction ring is attached to abrake disc cup with sliders.

This design allows the brake discs to freelyexpand in the radial direction. Thissignificantly improves the thermal shockresistance, increasing the service life of thebrake disc.

At the same time, this type of connectionhas a favorable effect on the deformation ofthe friction ring under temperature loading.This reduces noise during brake application.

A positive result of this design is the weightsaved by manufacturing the brake disc cupfrom aluminum. The specially formedcooling ribs provide a robust constructionwith optimal flow-through.

Specially shaped rims and an air guidemove the air stream directly to thebrake disc.

Rear Wheel Brakes

The Phaeton rear wheel brakes arehigh-performance, ventilated disc brakes.

They use newly developed aluminumbrake calipers.

The parking brake feature is integrated intothe rear brake calipers.

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Friction Ring

Slider

AluminumBrakeDisc Cup

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34

Brakes

Foot Parking Brake

The Phaeton uses a foot-actuated parkingbrake. It is distinguished by its low weight,minimum release force, and responsivedesign. The main components of theparking brake pedal assembly aremanufactured from aluminum alloy.

The parking brake is located in theleft side of the footwell above the footrest.The parking brake is applied by pressingthe pedal.

When the driver presses the foot parkingbrake pedal, a control cable transfers theapplied force to a lever mechanism underthe floor of the vehicle. Here, the force isdivided over two brake cables, whichoperate the actuating mechanisms on therear wheel brakes.

The parking brake is released by pulling therelease lever by hand.

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Release Cable

Pedal

Control Cable

Release Lever

35

Brakes

Foot Parking Brake Coil Spring

The coil spring, which acts on a drum, takeson the brake locking function. The springslides on the drum and expands due to thedirection of movement.

If the counter force of the brake moves thespring in the other direction, it pullstogether and increases the friction betweenthe coil spring and drum. Thus, the pedallocking action is almost completely steplessand noiseless.

An additional plastic spring producesthe typical click sound when the pedalis pressed.

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Release

The diameter of thecoil spring becomeslarger when the springexpands. The coil springcan move on the drum.

Lock

The coil spring tightensaround the drum whenthe pedal moves inthe opposing direction.

When the driver pulls the release lever,the retainer of the release cable is drawnupward. This expands the coil spring, or inother words, the spring becomes moveableand the pedal can return to the initialposition. This principle requires lowrelease forces.

SSP277/156a

Retainerfor ReleaseCable

Coil Spring

ReleaseCable

Drum

Pedal

Control Cable

Plastic Spring

Cable Retainer

Coil Spring

Drum

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36

Brakes

Actuation of the Rear Wheel

Parking Brakes

When the driver applies the foot parkingbrake, the brake cables actuate theparking brake lever on the brake caliper.The actuating shaft turns and performsa stroke.

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The mounting of the actuating shaft onthree balls, which are positioned on asloped disc, produces the stroke. Thestroke movement actuates the pistonwhich clamps the brake caliper and pressesthe brake pads against the brake disc.

Parking Brake Cable

Parking Brake Lever

37

Brakes

Automatic resetting

The increase in clearance that results frombrake pad wear must be compensated forby the caliper.

A turning action of the resetting nut onthe threads of the push bar resets theclearance to compensate for the increase inclearance that results from brake pad wear.

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Brake Pad

Brake Disc

Caliper Piston

Spring Washer

Resetting Nut

Compression Spring

Housing

Actuating Shaft

ParkingBrakeLever

Sloped Disc

Push Bar

38

Brakes

When the driver applies the service brakesand hydraulic pressure develops in the brakesystem and brake calipers, the piston movesin the housing toward the brake disc.

The resetting nut is carried in the piston bya spring washer.

If the clearance increases due to brake padwear, it is compensated in the threadsbetween the push bar and resetting nut.

Push Bar

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The force of the compression spring onthe resetting nut acts against the pressingdirection of the piston. This opens thecone clutch between the resetting nut andthe piston.

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Increased Clearance

Resetting Nut

Cone Clutch

Push Bar

Resetting Nut

39

Brakes

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The push bar is held by the compressionspring. The turns of the threads betweenthe push bar and resetting nut are engagedin this resetting sequence.

The coarse-pitch threads between the pushbar and resetting nut produces a turningmoment on the resetting nut. The coneclutch between the resetting nut and thepiston opens far enough so that theresetting nut can turn on the threads of thepush bar by the amount of the increasedclearance in the brake application direction.

This resetting process takes places alsowhen the brake caliper is relieved, that is,after the braking process.

Thus the brake wear that occurs whilebraking is directly and non-incrementallyreset.

The nominal clearance is the play betweenthe resetting nut and push bar threadsdetermined by tolerances.

When the pressure on the brake caliper isrelieved, a clearance between the brakepads and brake disc appears.

Nominal Clearance

Clearance

Push Bar

Resetting Nut

Push Bar

Resetting Nut

40

Brakes

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Structure of the Parking Brake Cable

Brake Lines and Cables

Hydraulic Brake Lines

The brake lines are galvanized steel pipesthat have a corrosion-resistant surfaceprotection provided by the zinc plating andan additional polyamide coating.

These lines are attached to the body withplastic holders. A robust, hard outer shell isused for attachment. Soft injectedelements are used for noise insulation.

The flexible connections in the lines to thefront and rear axles are brake tubes. Theinner tube consists of a material thatprevents water absorption into the brakefluid. For stability, this tube has severalbraided fiber sleeves, which are protectedagainst external influences by rubber.

Steel Cable

Lining Tube(Polyamide)

Protective Shell(Polyurethane)

Polyamide Coating

Profile Wire Spiral

The lines the engine compartment aswell as the connection lines betweenthe ABS Hydraulic Unit N55 and the brakebooster are connected to plastic tubeswith braided steel sheathing.

The structure of these lines also reducesnoise transfer from the ABS Hydraulic UnitN55 during operation.

Foot Parking Brake Cables

The foot parking brake cables are sheathedin polyamide and greased to preventcorrosion and reduce friction forces.

41

Pedal Cluster

The bearing block of the pedal cluster ismade of aluminum alloy. It is designed tobreak at a specific location in the event of acrash. This reduces the likelihood of injuryto the driver’s lower legs and feet.

Brakes

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Custom covers are installed on the pedalsfor appearance purposes.

Bosch 5.7 Antilock Brake System

The Phaeton uses the Bosch 5.7 AntilockBrake System (ABS) with ElectronicStabilization Program (ESP) and hydraulicBrake Assist.

42

Brakes

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Bosch 5.7 ABS Features

• The hydraulic unit and control unit areintegrated into a single ABS HydraulicUnit N55.

• The brake pressure sensing Sender 1for Brake Booster G201 screws directlyinto the ABS Hydraulic Unit N55.

43

Brakes

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• An ESP feature without preloadingis provided.

• The ESP has EDL, TCS, and ABS featuresas well as Brake Assist.

Sender 1 forBrake BoosterG201

ABS Hydraulic Unit N55

44

Brakes

Active Wheel Speed Sensors

The Bosch 5.7 ABS uses four active ABSwheel speed sensors:

• Right Rear ABS Wheel SpeedSensor G44

• Right Front ABS Wheel SpeedSensor G45

• Left Rear ABS Wheel SpeedSensor G46

• Left Front ABS Wheel SpeedSensor G47

Each ABS wheel speed sensor is made of amaterial that changes its electricalconductivity depending on a magnetic field.

An electronic switch converts thecurrent fluctuations induced in the sensormaterial into voltage fluctuations at thesensor output.

If the signal wheel moves relative tothe sensor, the sensor generates asquare-wave voltage signal at thecorresponding frequency depending onthe speed of rotation.

The advantage compared to previouslyused systems is that it is possible toexactly detect the speed of wheel rotationright down to zero rotation.

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ABS WheelSpeed Sensor

Signal Wheel

Sensor Electronics

Sensor Housing

45

Brakes

Tandem Master Cylinder

with Brake Booster

The tandem master cylinder has a strokeof 1.42 inches (36 mm). The diameter ofthe main brake cylinder is 1.063 inches(26.99 mm). The tandem master cylinderwith brake booster has light-weightconstruction and the followingadditional features:

• The central valves of the tandem mastercylinder guarantee the shortest applicationdistance at the pedal combined withreliable, self-priming ESP functionality.

• The active (electrically activated) brakebooster variant use in brake systems onvehicles that have Adaptive CruiseControl (ACC) represents the corecomponent for activation with automaticdelay of the vehicle in ACC operation andhelps ensure regulated, automatic delay.

Vehicles with ACC have activebrake boosters. For more detailedinformation, please refer toThe Phaeton Adaptive CruiseControl, Self-Study ProgramCourse Number 898303.

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Brake Booster MembranePosition Sensor G420(Only in Vehicles with ACC)

Connection for Release Switch(Only in Vehicles with ACC)

Magnetic Coil for Brake Pressurein Brake Booster N247(Only in Vehicles with ACC)

46

Wheels and Tires


System Overview

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Antenna forTire Pressure Check,Rear Right R62

Antenna for TirePressure Check,Rear Left R61

Antenna forTire Pressure Check,Front Right R60

Antenna for TirePressure Check,Front Left R59

Tire PressureMonitoringControl ModuleJ502

Instrument ClusterCombinationProcessor J218

Sensor forTire PressureSpare TireG226

Sensor forTire PressureRear RightG225

Sensor forTire PressureRear Left G224

Sensor forTire PressureFront Right G223

Sensor forTire PressureFront Left G222

Function SelectorSwitch II E272

47

Wheels and Tires


System Function

The tire pressure monitoring systemcontinuously monitors the tire pressurewhile driving and when the vehicleis stationary.

The tire pressure monitoring system usedin the Phaeton is a five-wheel system.The spare wheel is also monitored andincluded in the system messages.

A measuring and transmitting unit mountedin each tire valve sends radio signals atregular intervals to the antennas mountedin each wheel housing. The signals are thenpassed on to the Tire Pressure MonitoringControl Module J502.

The Tire Pressure Monitoring ControlModule J502 evaluates the tire pressuresor changes in tire pressure and sendscorresponding system messages tothe Instrument Cluster CombinationProcessor J218. The system messagesthen appear on the Display Unit inInstrument Cluster Y24.

If the driver has selected the “Vehicle”menu in the Front Information DisplayControl Head J523, the system messagesfor tire pressure monitor are displayed.

The system recognizes thefollowing situations:

• Gradual pressure loss:The system informs the driver in time tobe able to correct the tire pressure.

• Sudden pressure loss:The system warns the driver immediatelywhile driving.

• Excessive pressure loss when thevehicle is stationary:The system warns the driver immediatelyafter the ignition is turned on.

48

Wheels and Tires

Sensors for Tire Pressure

The tire pressure monitoring system on thePhaeton uses five sensors for tire pressure:

• Sensor for Tire Pressure Front Left G222

• Sensor for Tire Pressure Front Right G223

• Sensor for Tire Pressure Rear Left G224

• Sensor for Tire Pressure Rear Right G225

• Sensor for Tire Pressure Spare Tire G226

The sensors for tire pressure are screwedto the metal valves and can be reusedwhen the wheels or rims are changed.

The following components are integratedinto each sensor for tire pressure:

• Transmitter antenna

• Pressure sensor

• Temperature sensor

• Measuring and control electronics

• Battery

The pressure sensor detects the actual tireinflation pressure (absolute pressuremeasurement). The pressure is then sentto the Tire Pressure Monitoring ControlModule J502 for evaluation.

The temperature signal is used forcompensating temperature-dependentpressure changes in the tires as well as fordiagnostic purposes.

The Tire Pressure Monitoring ControlModule J502 performs the temperaturecompensation. The measured tire inflationpressures are normalized to a temperatureof 68°F (20°C).

The pressure sensor, temperature sensorand measuring and control electronics areintegrated into one intelligent sensor.

When the driver selects “Store pressures,”the tire inflation pressures are againnormalized to 68°F (20°C).

To avoid inaccurate settings,special care must be taken toensure that the tire pressures arechecked, corrected, and storedwhen the tires are cold.

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Battery

Measuring andControl Electronics

TemperatureSensor

PressureSensor

TransmitterAntenna

Metal Valve

Sensor forTire Pressure

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49

Wheels and Tires

Antennas for Tire Pressure Check

The tire pressure monitoring system on thePhaeton uses four antennas for tirepressure check:

• Antenna for Tire Pressure Check, FrontLeft R59

• Antenna for Tire Pressure Check, FrontRight R60

• Antenna for Tire Pressure Check, RearLeft R61

• Antenna for Tire Pressure Check, RearRight R62

The following information is sent to theantennas for tire pressure check from thetransmitter antennas of the sensors fortire pressure:

• Individual identification number (ID code).

• Current tire inflation pressure(absolute pressure).

• Current tire air temperature.

• Condition of the integrated battery.

• The status, synchronization, andcontrol information necessary forsecure data transfer.

SSP277/1210000598100

0000578100

0000755100

0000602300

0000597200ID codes

Each sensor for tire pressure has anindividual identification number(ID code), which is used for“own wheel recognition.”

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Sensor forTire Pressure

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Antenna forTire PressureCheck

50

Wheels and Tires

Function

The antennas for tire pressure checkreceive radio signals from the sensors fortire pressure and transfer these signals tothe Tire Pressure Monitoring ControlModule J502 for further processing.

The four antennas for tire pressurecheck used on the Phaeton tire pressuremonitoring system are mounted in thewheel housings behind the wheelarch shells.

They are connected to the Tire PressureMonitoring Control Module J502 using highfrequency antenna lines and are allocatedaccording to their location.

The antennas for tire pressure check receiveall radio signals transmitted in their receptionand frequency range. Each antenna for tirepressure check receives the radio signals ofall wheel sensors that are in range.

The Tire Pressure Monitoring ControlModule J502 filters and selects the radiosignals so that it can process the correctinformation.

The spare wheel does not havea separate antenna for tirepressure check assigned to it.

The antennas for tire pressure checkreceive the radio signals that the Sensor forTire Pressure Spare Tire G226 transmits(data messages) and transfer the signals tothe Tire Pressure Monitoring ControlModule J502.

The Tire Pressure Monitoring ControlModule J502 recognizes and stores the“fifth wheel” as the spare wheel using ownwheel and position recognition.

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51

Wheels and Tires


Functional Diagram

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Components

G222 Sensor for Tire Pressure Front LeftG223 Sensor for Tire Pressure Front RightG224 Sensor for Tire Pressure Rear LeftG225 Sensor for Tire Pressure Rear RightG226 Sensor for Tire Pressure Spare Tire

J218 Instrument Cluster Combination ProcessorJ502 Tire Pressure Monitoring Control ModuleJ523 Front Information Display Control Head

R59 Antenna for Tire Pressure Check,Front Left

R60 Antenna for Tire Pressure Check,Front Right

R61 Antenna for Tire Pressure Check, Rear LeftR62 Antenna for Tire Pressure Check, Rear Right

Color Codes

Input Signal

Output Signal

Positive

Ground

Convenience CAN Data Bus

Gold Contact

G222 G223 G224 G225 G226

R59 R60 R61 R62

15 +

J502

J523J218

S

52

Wheels and Tires

Warning Messages

High-priority warnings –

sudden pressure loss

Target tire pressure stored via themenu. The system calculates the targetpressures relative to 68°F (20°C) fromthe respective inflation pressures.

The pressure falls below the codedminimum pressure of, for example,1.9 bar (27.9 psi (190 kPa)) for Phaetonwith W12 engine.

High-priority warning due to suddenpressure loss greater than 0.4 bar(5.8 psi (40 kPa)) below the storedtarget tire pressure.

Dynamic high-priority warning onsudden pressure loss greater than0.2 bar (2.9 psi (20 kPa)) relative tothe last transmitted pressure value.

Flat Tire!

The wheel electronics send data messagesevery 54 seconds.

If the wheel electronics detect a suddenchange in pressure greater than 0.2 bar(2.9 psi (20 kPa)) per minute, it transmits in850 ms cycles.

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1 bar(14.5 psi)(100 kPa)

30 60

Time in Seconds

Pre

ssu

re

53

Wheels and Tires

Low-priority warnings –

slow pressure loss

If the driver has inflated thetires to pressures critical todriving dynamics, the systemalso issues warnings.

The difference in targetpressures on one axle may notexceed 0.4 bar (5.8 psi (40 kPa)).

The difference in targetpressures between the axlesmay not exceed 0.5 bar(7.3 psi (50 kPa)).

If the spare tire pressure fallsbelow its stored target pressureby more than 0.4 bar (5.8 psi(40 kPa)), a low-priority warninglikewise appears.

Low-priority warning due to pressure lossbetween 0.2 and 0.4 bar (2.9 and 5.8 psi(20 and 40 kPa)) below the stored targettire pressure.

High-priority warning due to pressureloss greater than 0.4 bar (5.8 psi (40 kPa))below the stored target tire pressure.

The wheel electronics send data messagesevery 54 seconds.

If the wheel electronics detect a suddenchange in pressure greater than 0.2 bar(2.9 psi (20 kPa)) per minute, it transmits in850 ms cycles.

Check Pressures!

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1 bar(14.5 psi)(100 kPa)

30 60

Time in Seconds

Pre

ssu

re

System Fault!

54

Wheels and Tires

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Faulty WheelOn Board!

Warnings in the Display Unit

in Instrument Cluster Y24

The small symbol is always displayed.

The large symbol only appears when the“Tire pressure monitor” menu is open.It disappears when another menu opens.

Display whenfaulty wheelon board.

Display duringsystem fault.

Display duringradio fault.

Display whenswitching off.

Display duringthe learn phase.

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SystemIs Learning!

SystemSwitched Off!

Warning CurrentlyNot Possible!

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Controls

The tire pressure monitoring system mainmenu appears on the Front InformationDisplay Control Head J523 when the“VEHICLE” function key is pressed.

The following functions are stored:

• Switch on/off tire pressuremonitoring system.

• Switch on/off spare wheel monitoring.• Inflation information.• Adopt current pressures.

The driver can specify and set the tirepressures to be monitored within the limitscoded according to the vehicle series.

After pressing the “Adopt current tirepressures” function button and thenconfirming the pressures, the systemstores the current tire inflation pressures atthe current tire inner temperatures for theirrespective ID codes.

1 2 3 4 5 6

CLIMATE

RESET

FM

AM

CD

SCAN

MAP

VEHICLE

NAV

NAV SET

AUDIO

TRIP DATA

SETTINGS

MANUAL

BAL/FAD

ON/DARK

HELP

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“VEHICLE”Function Key

Pressing the key also starts a new learnprocess for wheel assignment. To avoidreceiving from external wheel electronicswhile learning, the system learns onlywhen travelling faster than 3.1 mph(5 km/h). The learning process is completeafter about 15 minutes driving time.

Tire pressure monitoring main menu with

high-priority warning for rear right tire

The driver isresponsible forcorrectly settingthe tire pressuresto be monitored.

TPM

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Target pressuresin [Bar]at 20°C

Adopt currentpressures

Spare wheelmonitoring

Inflationinformation

Vehicle

Wheels and Tires

55

Notes

56

57

Knowledge Assessment

An on-line Knowledge Assessment (exam) is available for this Self-Study Program.

The Knowledge Assessment may or may not be required for Certification.

You can find this Knowledge Assessment at:

www.vwwebsource.com

From the vwwebsource.com Homepage, do the following:

– Click on the Certification tab

– Type the course number in the Search box

– Click “Go!” and wait until the screen refreshes

– Click “Start” to begin the Assessment

For Assistance, please call:

Certification Program Headquarters

1 – 877 – CU4 – CERT(1 – 877 – 284 – 2378)

(8:00 a.m. to 8:00 p.m. EST)

Or, E-Mail:

[email protected]

Volkswagen of America, Inc.3800 Hamlin RoadAuburn Hills, MI 48326Printed in U.S.A.August 2003

Documents

The Phaeton Chassis Design and Function