Get Running gear Guide for Audi RS E Tron Gt 4 Door First Generation (2021-2026)

Running gear

Overview

The main system components of the running gear on the Audi e‑tron GT and the Audi RS e‑tron GT are largely identical. Any differ-

ences will be mentioned specifically in the following chapters. If information about the Audi e‑tron GT is given and no differences

are mentioned, the information also applies to the Audi RS e‑tron GT.

In the standard version, the Audi e‑tron GT is equipped with a steel spring running gear with electronic damping control. Air sus-

pension is available as an option in conjunction with electronic damping control (adaptive air suspension). The Audi RS e‑tron GT is

equipped with adaptive air suspension as standard. Both of the running gears are new developments or evolutions of those in cur-

rent Audi models.

The four-wheel steering system is available as optional equipment for the Audi e-tron GT. One of the highest priority development

goals was to achieve a low vehicle weight. The main axle components are therefore made of aluminum. Running gear control

unit J775 is also the coordination platform for the running gear systems in the Audi e‑tron GT.

If the required conditions have been met, recuperation takes place via the generator mode of the electric motor(s).The total brak-

ing power is then obtained from the hydraulic braking power and the braking power provided by the electric motor(s). The complex

regulation of these processes is performed by an electromechanical brake servo in conjunction with a 9th generation ESC system.

As on the Audi e-tron, the driver can set the level of recuperation by pulling the paddle levers on the steering wheel.

The standard version of the Audi e-tron GT is equipped with a generously proportioned steel brake system. Carbide-coated brake

discs or a ceramic brake system are available as optional equipment. The RS model has the carbide-coated brake discs as standard

equipment and can be equipped with the ceramic brake system as an option.

The range of available wheels spans from 19” (for the e-tron GT) and 20” (for the RS e-tron GT) in the standard equipment version,

to optional 21” wheels. Specially developed optimised rolling resistance tires reduce rolling resistance and help to increase the

range.

The third-generation Tire Pressure Monitoring System with direct measurement completes the comprehensive standard equip-

ment.

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Axles

Overview

The axles of the Audi e‑tron GT are evolutions on the basis of the axle technology of the Porsche Panamera and Porsche Taycan.

Double wishbone axles are used at the front and the rear. The rear axle is a double wishbone axle with separate upper wishbones.

This means that one wishbone is used for the lower section while the upper section is "split” into two individual wishbones.

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This type of axle construction mainly provides packaging benefits. In the development of this vehicle, a particular emphasis was

placed on lightweight construction. The subframe, wheel bearing housings and wishbones on the front axle are made of

aluminum On the rear axle, this applies to the subframe, hub carriers, wishbones and track rods.

Front axle

System components

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Subframe

The subframe is a welded construction made of four aluminum node castings connected by aluminum extrusions. This type of con-

struction allows for high rigidity and low weight. The lower wishbones, the steering rack, the anti-roll bar and the assembly mount-

ings are fitted on the subframe. Two reinforcement panels which are bolted to the subframe from below are used in addition to

increase rigidity.

The subframe is fixed in place on the vehicle body with bolts at six mounting points.

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Wheel bearing housings

The wheel bearing housings are hollow aluminum castings. The upper and lower wishbones and the steering rack’s track rods are

connected to them by ball joints. The brake calipers and wheel hubs/wheel bearings are bolted directly onto them. In the upper

section, they also provide the connections for the anti-roll bar coupling rods.

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Wishbones

The upper and lower wishbones are forged aluminum components. This manufacturing technology provides high mechanical rigidi-

ty under compression, tensile and bending loads while keeping the mass of the components low. The upper wishbones are connec-

ted to the vehicle body with large bonded rubber bushes. The lower wishbones are fitted in the subframe on the vehicle body side.

A bonded rubber bush is also used for the front mounting position; the mounting at the rear has a hydraulically damped bush. The

suspension struts are also connected to the lower wishbones.

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Hydro-bush of lower wishbone

Lower wishbone

Upper wishbone

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Anti-roll bar

Tubular anti-roll bars with coupling rods are used. These are coupled at the wheel bearing housings. The anti-roll bars are mounted

on the subframe in bonded rubber bushes.

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Wheel hub/wheel bearing

The wheel hub and wheel bearing are flanged to the wheel bearing housings as one unit. The wheel hub can be pressed out of the

wheel bearing in service. A magnetised impulse ring, which works as an impulse sender for the wheel speed sensor, is integrated in

the wheel bearing seal.

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Suspension/damper strut

Single-tube dampers (gas struts) are standard equipment and can be regulated in non-compression and compression stages. The

regulating valve inside (which has continuous adjustment) is activated by running gear control unit J775 via a wire going through

the piston rod. In the neutral condition (not electrically activated), the damping force is low (“soft” characteristic).

Steel springs are used in the standard equipment version.

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Service operations – new special tools

Several tools which were previously only used for assembly work on Porsche vehicles are used to remove/install axle components.

One example is the spring compressor VAS 6908, which is used to remove/install the suspension strut on the front axle (refer to

Workshop Manual).

Rear axle

System components

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Subframe

The subframe serves as the mounting for the wishbones, the anti-roll bar and the steering rack for the rear wheel steering (option-

al). It is decoupled from the vehicle body by four hydraulically damped bushes and made of aluminum gravity die casting.

If the vehicle is equipped with four-wheel steering, the rear wheel steering module is fitted instead of the cross member.

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Hub carriers

The hub carries are aluminum castings. The wishbones and track rods are connected with bonded rubber bushes. The wheel hubs/

wheel bearings are secured with flange connections. The brake calipers and the actuators of the electromechanical parking brake

are also connected to the hub carrier.

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Upper wishbones

The two upper wishbones are forged aluminum components. They are connected to the subframe and hub carrier with bonded rub-

ber bushes.

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Lower wishbones

The lower wishbones are made of aluminum and manufactured using the gravity die casting process. They are also connected to

the subframe and hub carrier with bonded rubber bushes. Cup-shaped indentations serve as mountings and supports for the

springs. The dampers are fitted in the outer section between the spring mountings and the connections for the hub carriers. The

coupling rods for the anti-roll bars are fitted in bonded rubber bushes at the side.

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Track rod

The track rods are forged aluminum components. They are connected to the subframe and the hub carrier via bonded rubber bush-

es. If the vehicle is equipped with four-wheel steering, the connection on the axle side is made in the forks of the rear axle steering

rack’s spindles.

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Wheel hub/wheel bearing

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A third-generation wheel bearing unit is used. The wheel hub and the wheel bearing form one unit which is flanged to the hub carri-

er. The wheel hub can be pressed out of the wheel bearing if necessary. A magnetised impulse ring, which works as an impulse

sender for the wheel speed sensor, is integrated in the wheel bearing seal.

Anti-roll bar

Tubular anti-roll bars with coupling rods are used. These are coupled at the lower wishbones. The anti-roll bars are mounted on the

subframe in bonded rubber bushes.

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Shock absorber

Single-tube dampers (gas struts) are fitted and can be regulated in non-compression and compression stages. The regulating valve

inside (which has continuous adjustment) is activated by running gear control unit via a wire going through the piston rod. In the

neutral condition (not electrically activated), the damping force is low (“soft” characteristic).

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Wheel alignment

The wheel alignment procedure corresponds to that of other Audi models. There are some differences when preparing the vehicle

for wheel alignment. The process is specified in the new Guided Function of the running gear control unit J775: “0074- Establish /

reset preconditions for vehicle alignment”.

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After successful changes to the wheel position values, sensors/systems affected must be re-adapted/calibrated. Please follow the

instructions in the Workshop Manual and the wheel alignment computer.

Special preparations must be made before starting wheel alignment on vehicles with adaptive air suspension and/or four-wheel

steering. The precise vehicle level required for wheel alignment must be set and height regulation must be deactivated at this level.

The wheels on the rear axle must also be tightly locked in zero position. On the Audi e-tron GT, these functions no longer need to be

activated separately via the corresponding control units. This task is undertaken by the previously mentioned function “0074- Es-

tablish / reset preconditions for vehicle alignment”. The specified function is also used for vehicles with electronic damping control,

although in this case without the functions specific to air suspension.

Front axle

On the front axle, the toe settings for each wheel can be adjusted at the track rods.

The camber values can be aligned by moving the subframe to the side.

Rear axle

The toe setting at each wheel can be adjusted at the bolted connections for the track rods with the subframe or with the spindle of

the rear axle steering rack.

The camber values on the left and right sides can be set independently of each other. The eccentric bolts used to connect the front

lower wishbones to the subframe can be used to do this.

A new special tool (T90009) is used to set the toe.

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Adaptive air suspension

Overview

Adaptive air suspension with electronic damping control is standard equipment on the Audi RS e-tron GT and optional equipment

on the Audi e-tron GT. The system’s construction fundamentally corresponds to the adaptive air suspension systems used on other

Audi models, in particular the Audi Q7 (type 4M). However, the system components partially vary and are presented in detail below.

Air springs with three separate air chambers are being used in an Audi model for the first time.

This allows different air spring volumes to be achieved using integrated electrically switchable valves. Another new feature is that

the acceleration of unsprung masses can be detected by four separate sensors. The running gear control unit J775 remains the con-

trol centre for the air suspension and damping on the Audi e‑tron GT.

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System components

Running gear control unit J775

Overview

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As with other Audi models on the MLB platform, the running gear control unit is also the central regulating unit for various running

gear systems on the Audi e‑tron GT. The tasks of the control unit include damping control and regulation of the vehicle level (adap-

tive air suspension). The basis of this is an analysis of the current dynamic driving state (evaluation of longitudinal, lateral and ver-

tical acceleration along with the yaw, roll and pitch rate) in real time. These data (from external sensors (refer to image

“684_342”)) are the basis for determining the driving state. The control unit communicates via FlexRay channel A, which is fitted in

the luggage compartment (left-side).

Data transfer

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Service operations

The following new features regarding the air suspension are present in the service functions of control unit J775 in the Audi e-

tron GT:

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A new function “0074 - Replacement work on air suspension system” has been introduced to replace air springs. In the sub-menu,

the user can select whether just one air spring is to be replaced or whether the entire system is to be bled/filled up. As previously,

the vehicle must be on a lifting platform with its wheels off the ground before work is started. This prevents damage to the air

springs which are bled. Regulation by the program is deactivated at the beginning of the bleeding process. The system is bled on

the basis of an accompanying pressure measurement up to a maximum remaining air spring pressure of approx. 4 bar. Only then

can the air system be opened safely to remove the air spring affected.

The system is filled using the accumulator. A minimum air pressure of 12 bar is required to do this. If the measured accumulator

pressure is lower, the accumulator is initially filled to a pressure of >12 bar. The system is then filled a maximum of 10 times. If

the minimum pressure cannot be reached, the mechanic is informed that there is a system fault (e.g. a leak). The air spring(s) are

also filled on the basis of an accompanying pressure measurement. An air pressure of between approx. 4 bar and a maximum of

7.2 bar will be set. The height regulation will be reactivated after the system has been filled successfully.

Note

It is very important that you observe the information in the Workshop Manual related to handling the air springs. In-

correct handling may cause damage or premature failure.

If the “Venting / filling entire suspension system” function is performed, the air dryer is regenerated after the system has been

filled. This involves fully bleeding the accumulator and then filling it back up to a pressure of approx. 18.5 bar. In the bleeding

process, dry air flows through the dryer and transports the moisture bound in the drying granulate out of the system into the at-

mosphere.

Additional diagnosis functions correspond to those in other Audi models. After removal/installation of certain components (e.g.

control unit J775, vehicle level senders), the vehicle height level must be re-adapted on vehicles with adaptive air suspension or

electronic damping control.

System faults are indicated to the driver via the activation of the familiar air spring symbol in conjunction with an explanatory text.

The relevant messages are described in the Owner's Manual. Depending on the fault category, the symbol is either red or yellow, as

on previous vehicles.

Air spring strut, front axle

The air springs on the front axle consist of three differently-sized chambers which are connected together. Two electrically switcha-

ble valves can be used to separate chambers. One valve separates volume 1 from volume 2, the other separates volume 1 from

volume 3. There is no direct link between volume 2 and volume 3. As a result, it is possible to achieve three different air volumes.

The larger the air volume achieved is, the smaller the spring rate will be. This makes spring extensions and compressions corre-

spondingly more comfortable. Smaller air volumes with larger spring rates are more suitable at high speeds or for dynamic driving.

Because the air volume can be changed quickly depending on the situation, it is particularly easy to regulate the suspension to react

to different driving conditions.

Air spring volumes:

Volume

Feature

Volume 1 + volume 2 + volume 3

Volume 1 + volume 2

Volume 1 + volume 3

Volume 1

Highest volume, lowest spring rate, most comfortable setting

Medium volume

Small volume, high spring rate, dynamic setting

Smallest volume, highest spring rate, most dynamic setting

At vehicle speeds of < approx. 220 km/h and little or no longitudinal or lateral influences, all three air volumes are usually activa-

ted. At high speeds or in the event of increasing dynamic influences (lots of corners, braking and acceleration), volumes 2 or 3 may

be switched off as necessary.

The switching valves are directly activated by running gear control unit J775 via two discrete wires. In their neutral, non-activated

status, both valves are open (low spring rate - “soft” suspension). This status is present after the vehicle has been parked and as

part of certain faults which lead to regulation being deactivated.

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Air spring on rear axle

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Springs and dampers are fitted in a separate layout on the rear axle as individual components. The air springs on the rear axle also

consist of three chambers which are connected together. Two electrically operated valves can be used to separate chambers. The

system works in the same way as the air spring system on the front axle.

Air supply unit

The compressor generates the relative system pressure of approx. 18 bar (maximum pressure approx. 25 bar). It compresses the

air drawn in via the intake silencer and the filter in a two-stage compression process. The electric compressor works with two pis-

tons. Its design and functions correspond to the component in the Audi Q7 (type 4M).

Reference

For further information, please refer to (refer to chapter “Chassis with air suspension and electronic damper control

(adaptive air suspension)”) in SSP 633 “Audi Q7 (type 4M) Chassis.”

The air supply unit is also fitted at the rear of the vehicle in the Audi e-tron GT. Rubber bushes ensure effective acoustic decoupling

and reduce the amount of structure-borne sound in in the body structure. Additional components of the air supply unit are the air

dryer and a solenoid valve for the boost function. The module also includes a pneumatically operated exhaust valve and a solenoid

valve to actuate it. The design and construction again correspond to that of the of the compressor module in the Audi Q7 (type 4M)

and the description in SSP 633.

A pressure relief valve is fitted in the compressor module of the Audi e‑tron GT. When air is released or pressure is dissipated in the

system, this ensures that the system pressure does not drop below 2 bar. The residual pressure valves fitted directly on the air

connections of the air spring struts on some other Audi models are also fitted on the Audi e‑tron GT. This ensures that a small air

pressure of approx. 1.5 bar remains in the air springs even in the event of a loss of pressure due to leakages in the lines.

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The electric motor is activated by a separate control unit which is fitted on the same bracket. As on the Audi Q7 (type 4M), activa-

tion is via a PWM signal. This makes it possible to start the motor “gently” without significant current peaks. A compressor-temper-

ature model has also been implemented on this control unit. It monitors the compressor temperature on the basis of the outside

temperature, vehicle speed and compressor running time. If defined temperature values are exceeded as part of this, regulating

processes upwards (raising the vehicle by actively running the compressor) are restricted or disabled until the temperature falls

accordingly. At this time, no mode changes can be made in Audi drive select which would require the vehicle to be raised.

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Solenoid valve block

The solenoid valve block has the same design and functional principle as in the Audi Q7 (type 4M).

Reference

For further information, please refer to (refer to chapter “Chassis with air suspension and electronic damper control

(adaptive air suspension)”) in SSP 633 “Audi Q7 (type 4M) Chassis.”

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Accumulator

The cylinder-shaped accumulator is made of aluminum and has a capacity of 8 litres. It is fitted in the rear of the vehicle. Regulat-

ing processes are performed using the pressure in the accumulator as a priority. This is done to limit the running time of the com-

pressor and to improve the interior acoustics. This requires sufficient pressure in the accumulator. The accumulator is filled up

while the vehicle is moving. The vehicle can be raised from the low level to the normal level approx. four times with the accumula-

tor filled up (to a system pressure of approx. 18 bar). The control unit determines the pressures in the air springs and the accumu-

lator by activating the correspondingly allocated solenoid valves and taking measurements via the pressure sensor integrated in

the solenoid valve block. These measured values form the basis for calculating the pressure differences between the accumulator

and the corresponding air spring. There must be a pressure difference of approx. 2 bar between the accumulator pressure and the

air spring pressure to increase the air volume in an air spring with the help of the accumulator. The accumulator also “provides” the

energy for the boost function, thereby ensuring that pressure can be built up quickly.

Reference

For further information on the pressure measurement and boost function, please refer to SSP 633 "Audi Q7 (type 4M)

Chassis".

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Vehicle level senders

The four vehicle level senders are Hall senders and provide the processed measured values to the running gear control unit in the

form of PWM signals. The four senders on the front and rear axles are identical. The brackets and linkages have been geometrically

adapted to the different connection points on the front and rear axle.

The service operations for removal and installation or replacement correspond to those for the vehicle level senders already in use

in other Audi models. Calibration is required after a sender is replaced: 0074 – Basic setting – Calibration of height sensors.

Any sensors/systems affected must subsequently be re-adapted/calibrated.

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Note

Please note the instructions in the Workshop Manual.

Vehicle level senders on front axle

Position of vehicle level sender on front axle – lever/linkage

connected to upper wishbone

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Vehicle level senders on rear axle

Position of vehicle level sender on rear axle – lever/linkage

connected to lower wishbone

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Wheel acceleration senders

The four wheel acceleration senders are being used on an Audi model for the first time. They detect the accelerations of the

wheels/the unsprung masses in the vehicle’s vertical (z) and lateral (y) directions. The measurement is made using the seismic

mass principle.

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Reference

Further information on how this measurement works can be found in SSP 458 "Audi A8 10 Running gear and suspen-

sion" in the section “Control unit for sensor electronics J849”.

The senders are fitted on the hub carriers of the front and rear axles.

The technical basis is the PSI5 sensor bus system (Peripheral Sensor Interface 5). This standardised system is very effective and has

low data transfer rates of <200 kbit/s. The sender is directly connected to the running gear control unit via a two-wire bus. The

sensor uses this bus both for data transfer and for its power supply from the running gear control unit. The running gear control

unit controls the communication via synchronisation impulses which are answered by the sender with corresponding data pack-

ages. The running gear control unit converts the signals received at a frequency of 120 Hz into digital square-wave signals and de-

codes the data received.

No further activities (calibration etc.) are required after a wheel acceleration sender is replaced in service.

It is possible to check whether the sender is fundamentally working properly by tipping it 180° out of its normal installation posi-

tion. If the sender is working correctly and the wiring is intact, negative actual values will be displayed as measured values.

Position of wheel acceleration sender on front axle

Position of wheel acceleration sender on rear axle

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Body acceleration senders

The four senders measure the acceleration of the vehicle body. This means the sprung masses in z direction and the longitudinal

accelerations in x direction. In the area of the front axle, the senders are fitted on the suspension turrets and at the rear they are

fitted on the side of the body behind the rear axle. Their design and functional principle largely corresponds to that of the wheel

acceleration senders. They are also connected to the running gear control unit via a PSI5 two-wire bus. In this case, the signal is

transmitted at 60 Hz; the measurement range is approx. +/- 1.6 g.

No further activities (calibration etc.) are required after a body acceleration sender is replaced in service.

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As with the wheel acceleration senders, it is possible to check whether the sender is fundamentally working properly by tipping it

180° out of its normal installation position. If the sender is working correctly and the wiring is intact, negative actual values will be

displayed as measured values.

Position of body acceleration sender in area of front axle

Position of body acceleration sender in area of rear axle

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Air lines, line connections, line connectors

The air lines which connect the air supply unit (solenoid valve block) to the air springs are fitted in the electrical wiring harness. The

air line to the accumulator is a moulding. Repairs to the air line system are also defined for the Audi e-tron GT. They largely corre-

spond to those undertaken for other Audi models.

Note

Please note the information in the Workshop Manual.

How the system works

The general function of the entire system (generating and dissipating pressure, boost function, integration of accumulator in regu-

lating processes, actuation of solenoid valves, pressure measurements) corresponds to that of the adaptive air suspension in the

Audi Q7 (type 4M).

Reference

For further information, please refer to (refer to chapter “Chassis with air suspension and electronic damper control

(adaptive air suspension)”) in SSP 633 “Audi Q7 (type 4M) Chassis.”

The main new feature is the introduction of the three-chamber air springs. Their functions and the resulting benefits are described

in the “System components” chapter. Integrating the wheel acceleration sensors in the entire system for the first time increases

precision when detecting the vehicle dynamics. The development aim was to retain the familiar operating and display concept from

other Audi models with adaptive air suspension. The desired mode can also be selected in Audi drive select on the Audi e‑tron GT.

The modes have been specially defined and applied to the Audi e‑tron GT.

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Regulating characteristics

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Various adaptive air suspension regulating characteristic maps are activated depending on the setting selected in Audi drive select.

Every mode has a defined vehicle level when the vehicle is stationary and a corresponding damper characteristic map. Automatic

changes to the levels are initiated by the regulation depending on the vehicle speed.

The different drive select settings correspond to three different vehicle levels. Every new driving cycle starts in “comfort” mode

automatically. If “Raise” mode is selected, the highest vehicle level is set (+20 mm compared to normal level).

The high level is ended automatically at 30 km/h and above. The vehicle is then lowered to the level of the previously selected

mode. In “comfort” and “dynamic” modes, the level is lowered by 10 mm if the vehicle speed exceeds 90 km/h for a period of

20 seconds. If the speed subsequently drops below 70 km/h for a period of 10 seconds, the vehicle is raised to the initial level of

“comfort/dynamic” mode. If the speed drops below 50 km/h, the vehicle is raised to this level immediately without a time delay. If

the vehicle speed exceeds 180 km/h for a period of 10 seconds, the level is lowered by 22 mm. If the speed is subsequently re-

duced to under 150 km/h for 10 seconds, the original level is restored. If the speed exceeds 120 km/h, the vehicle is raised to

lower level 1 immediately without a time delay. The aim of these automatic level reductions is, alongside increased driving stabili-

ty, to reduce air turbulence under the vehicle and in the wheel housings. Improving the aerodynamics positively affects the drive

power required and therefore also increases the range. This is the reason why low level 2 (-22 mm compared to “normal” level) is

activated when “efficiency” mode is selected.

It is only possible to lower the level when the vehicle is stationary if all four doors are closed. When the vehicle is parked (after bus

sleep mode), a one-off check of the vehicle level is made after eight hours by evaluating the measured values from the vehicle level

senders. If the accumulator pressure is sufficient, the vehicle is raised (if necessary) using the accumulator only (the compressor

does not run).

Electronic damping control

Electronic damping control with steel springs is standard equipment on the Audi e‑tron GT. The system’s design and functions fun-

damentally correspond to those of the systems used in other Audi models. A new feature is that the acceleration of unsprung mass-

es can be detected by four separate sensors. Single-tube dampers with inner regulating valves are used. The running gear control

unit J775 remains the control centre on the Audi e‑tron GT.

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The driver can specify the damping characteristics via the drive select setting selected.

System faults are shown via the familiar yellow warning symbol and a driver message.

The service operations are the same as for the systems which are already used on other Audi models for damping control. The same

sensors (vehicle level senders, body acceleration senders, wheel acceleration senders) as on the adaptive air suspension are used.

The information on these sensors in the adaptive air suspension chapter also applies to the electronic damping control.

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Steering system

Overview

Electromechanical power steering is used for the steering system of the Audi e-tron GT. Steering assistance is provided by a syn-

chronous electric motor fitted parallel to the axle. Manual adjustment for the steering column is included in the standard equip-

ment. An electrically adjustable steering column is available as an optional extra. Four-wheel steering is available as optional

equipment for the Audi e-tron GT. Three-spoke leather sport steering wheels are standard equipment.

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Electromechanical power steering system (EPS)

Design and function

In terms of design, operation and servicing operations, the EPS on the Audi e-tron GT corresponds to that used on other Audi mod-

els equipped with this steering system.

Reference

Information on the construction and function can also be found in SSP 644 “Audi A4 (type 8W)” (refer to article “Steer-

ing system”).

Steering assistance is provided by a synchronous electric motor fitted parallel to the axle. The motor’s torque is transmitted to a

ball screw drive via a toothed belt and sent to the steering rack as axial force.

The power steering control unit J500 communicates via FlexRay channel A.

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The main basic information for calculating the steering assistance consists of the steering torque which the driver introduces via

the steering wheel, the vehicle speed and the steering angle. The steering torque is transmitted to the control unit via a discrete

wire by the steering moment sender G269 contained in the module. The vehicle speed and steering angle are sent using FlexRay via

the ABS control unit J104. Two temperature sensors monitor the temperature of the control unit and that of the output stages. The

output stages provide the current to activate the motor while also taking the rotor position of the synchronous electric motor into

account. The control unit receives the information on the rotor position from within the module. It comes from a rotor position

sender in the electric motor.

The steering assistance is activated after the vehicle is started (terminal 15 on) and the drive system is activated.

The additional functions familiar from other Audi models, such as assist-based steering impulses (driver steering recommenda-

tion - DSR), “software” end stops and active steering resets have also been implemented on the Audi e-tron GT.

The EPS unit is fitted on the subframe behind the front axle. The module consists of the steering rack, the electric motor with

toothed belt and ball screw drive, the power steering control unit J500, the steering moment sender and the track rods and boots.

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Schematic diagram

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Response in the event of a fault

As on other Audi models, detected faults are indicated via the activation of the steering wheel symbol and explanatory messages.

Depending on the relevance, the symbol is shown in either yellow or red. The relevant messages are described in the Owner's Man-

ual.

Service operations

The track rods and boots can be replaced separately in service.

After replacing the module and coding the control unit online, the maximum steering wheel angles must be adapted and the steer-

ing angle sender G85 must be calibrated.

Steering column

Manual adjustment for the steering column is included in the standard equipment. An electrically adjustable steering column is

available as an optional extra.

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Steering wheel

Three-spoke leather sport steering wheels with flattened rims are used. The standard Audi e-tron GT steering wheel is perforated in

the grip area. All steering wheels are equipped with one of two versions of recuperation paddle levers. The standard steering wheel

of the RS model is equipped, as with all other optional steering wheels (except the Alcantara equipment option), with a fully perfo-

rated rim. The RS logo is also affixed to the RS model’s steering wheels. It is located under the opening of the centre spoke. Steer-

ing wheel heating is optional equipment for the Audi e‑tron GT; it is standard equipment for the RS model.

Standard equipment for Audi e-tron GT with full leather steering

wheel rim (perforated in grip area) and small paddle levers

Standard equipment for RS e-tron GT with full perforated leather

steering wheel rim, large paddle levers, steering wheel heating

and RS logo

All steering wheels have paddle levers for the driver to select the level of recuperation in overrun mode. The optional steering

wheels for the Audi e-tron GT and both steering wheels (standard and optional) for the RS model are equipped with large paddle

levers made of aluminum.

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The operating logic from vehicles with conventional drive systems has been used (as on the Audi e-tron):

When the (-) paddle lever is operated, the vehicle is decelerated by shifting down in overrun mode. The Audi e-tron GT decelerates

when the electric motor recuperates energy while it is in generator mode. The driver can increase/reduce the level of recuperation

in stages using the (+) or (-) paddle lever respectively. The menu option for manual recuperation must be set in the MMI to do this.

Two recuperation levels can be selected.

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Four-wheel steering

Four-wheel steering was first used in the Audi Q7 (type 4M). Four-wheel steering is available as optional equipment for the Audi e-

tron GT.

In terms of design (components), functions and servicing requirements, the four-wheel steering system corresponds to that used

on the Audi Q7 (type 4M).

Reference

For further information, please refer to (refer to chapter “Chassis with air suspension and electronic damper control

(adaptive air suspension)”) in SSP 633 “Audi Q7 (type 4M) Chassis.”

The rear axle steering rack also works in the same way as the one on the Audi Q7. The electric motor drives the spindle nut via the

drive belt. The rotational movement of the spindle nut is converted to linear movement of the spindle. The connected track rods

transmit the linear motion to the hub carriers and the wheels are steered in the same direction to the right or left (depending on

the direction of rotation of the electric motor). The system is self-locking due to the transmission ratio and the trapezoidal thread

of the spindle and the spindle nut.

The maximum wheel steering angle on the rear axle is 2.8° (approx. 5° on Audi A8 (type 4N) and Audi Q7 (type 4M)).

Brake system

Overview

Newly developed brake systems are used on the Audi e-tron GT and the RS model. The Audi e-tron GT has conventional brake discs

as standard equipment in conjunction with 6-piston fixed caliper brakes on the front axle and 4-piston fixed caliper brakes on the

rear axle. Brake discs with a tungsten carbide coating (PSCB) are being used on an Audi model for the first time. This brake system

is standard equipment for the Audi RS e-tron GT and is available as optional equipment for the Audi e-tron GT.

Ceramic brakes are available as optional equipment for both e-tron GT models. The brake calipers for the PSCB and ceramic brake

system are available in different colours. The front and rear brakes have separate brake circuits. About 65 % of the braking force is

transmitted at the front axle and about 35 % at the rear axle.

For the first time on an Audi model, the electromechanical parking brake on the rear axle is a drum brake. The brake drum is

formed by the hub of the brake disc. As on other Audi models, the regulating software for the parking brake is in the ESC control

unit.

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To ensure that the requirements that the electric drive system makes of the brake system (brake blending, recuperation etc.) are

met, an electromechanical brake servo is fitted on the Audi e-tron GT in conjunction with a powerful ESC system of generation 9.2.

These systems make autonomous braking maneuvers independent of the driver possible.

The components and dimensions of the brake system may vary from those shown in the overview in some markets in order to con-

form to country-specific regulations.

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109

Brake system

Type of brakes

Front axle

Rear axle

Conventional brake system

6-piston fixed caliper brakes

4-piston fixed caliper brakes

Standard equipment for Audi e-tron GT

Cast iron brake discs

360 x 30 mm

358 x 28 mm

Steel brake with tungsten carbide coating

6-piston fixed caliper brakes

4-piston fixed caliper brakes

Standard equipment for Audi RS e-tron GT,

optional equipment for Audi e-tron GT

Brake discs with tungsten carbide coating Brake discs with tungsten carbide coating

410 x 38 mm

365 x 28 mm

Special brake pads

Ceramic brake system

10-piston fixed caliper brakes

4-piston fixed caliper brakes

Optional equipment for both models

Ceramic brake discs

420 x 40 mm

Ceramic brake discs

410 x 32 mm

Special brake pads

All four wheels are equipped with brake pad wear detection.

Steel brake with tungsten carbide coating

This brake system is being used on an Audi model for the first time. It was developed by Porsche AG and has already been success-

fully used on some Porsche models. The main difference compared to conventional brake systems is the coating on the friction sur-

faces of the brake discs, which are cast iron composite brake discs. The friction surfaces have two coatings. First, an galvanic nickel

coating of approx. 10 micrometres is applied to the cast iron base plate. This coating is designed to inhibit cracks and provide cor-

rosion resistance. The actual tungsten carbide friction coating of approx. 40 - 200 micrometres is applied to the nickel layer. Tung-

sten carbide is a ceramic material which is added to many different hard metals. It is mainly used in toolmaking for components

and tools which need to be particularly wear-resistant.

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The following characteristics of the brake discs single them out in particular:

›

High corrosion resistance

Because of the high level of recuperation under braking, the hydraulic service brakes are used significantly less than on vehicles

with conventional drive systems. As a result, corrosion resistance is very important, both functionally and from the perspective

of the visual impression given by the vehicle.

›

Large wear resistance

Compared to a conventional brake disc, the service life is approx. 30 % longer.

Better performance

Thanks to the friction torque being built up quickly, the response is better than that of a conventional brake disc. The friction

remains more stable during a braking procedure. As a result, the feared brake fade (a decrease in the braking efficiency at very

high brake temperatures) is reduced significantly.

Specially developed brake pads have been used to be able to make the best use of the positive characteristics of the brake discs.

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Steel brake with tungsten carbide coating – 6-piston fixed

caliper on front axle

Ceramic brake with 10-piston fixed caliper on front axle

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Electromechanical brake servo

Overview

With its electric drive, the normal requirements for achieving the braking function both without recuperation and at different levels

of recuperation also apply to the Audi e-tron GT. Based on previous experience, the driver expects a braking effect which corre-

sponds to the pressure placed on the brake pedal. Depending on the recuperation taking place and the braking power being provi-

ded by the electric drive motor(s), the “remaining” braking effect must be provided by the hydraulic brake system. This is not possi-

ble with a conventional pneumatic brake servo with a fixed ratio of pedal force to piston rod force of the brake master cylinder.

These complex requirements can only be met by an electromechanical brake servo.

The electromechanical brake servo is able to induce brake pressure independently of the driver. When recuperation is taking place,

the hydraulic brake pressure can be restricted to the level required. Alternatively, brake pressure can be generated actively without

being initiated by the driver if other systems request it (e.g. adaptive cruise assist/ACC).

Design and function

This complex module consists of brake servo control unit J539, a two-stage gear drive, an electric motor to drive the gearing, a

distance sensor and the coupling rod which connects to the brake pedal.

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111

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Excepting the gearing technology used, the design and functions of the second generation electromechanical brake servo corre-

spond to those of the systems already in use on other Audi models.

Reference

Further information on how an electromechanical brake servo works can be found in Service TV programme 0413 TV

"A3 Sportback e-tron - Electromechanical Brake Servo".

The brake servo on the Audi e-tron GT works on the basis of a two-stage gear drive driven by an electric motor. The output of the

gear drive is a spindle shaft. When the brake servo is active, the rotational movement of the spindle shaft is converted into a longi-

tudinal movement of the spindle nut on the shaft. The spindle nut is in contact with a thrust piece which moves longitudinally and

passes the force on to a reaction plate. The force initiated by the driver via the brake pedal is also applied to this reaction plate by

the piston rod. The reaction plate operates the piston rod of the brake master cylinder, thereby generating brake pressure. The two

forces work independently of each other. The activation of the electric motor allows brake pressure to be generated even if the

driver does not press the brake pedal. A sensor designed on the principle of redundancy (brake pedal position sender G100, brake

pedal position sender 2 G836) detects the pedal travel initiated by the driver. In doing this, the control unit calculates the braking

torque desired by the driver and the amount of braking assistance required.

If other systems (e.g. deceleration request by the adaptive cruise assist) require that brake pressure be generated autonomously,

control unit J539 receives the message requesting implementation from ABS control unit J104.

Active accumulator VX70 used on the Audi Q7 e-tron and A3 e-tron vehicles is not fitted on the e-tron GT. The accumulator’s func-

tion is assumed by the ESC.

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Run-on – behaviour when terminal 15 is off

112

As on a conventional brake servo, the boosting function of the brake servo remains available for a certain period after terminal 15

has been switched off. While the pressure is fully dissipated within a few braking procedures on vehicles with pneumatic brake ser-

vo and conventional drive system, it remains fully available on the Audi e-tron GT for a defined period.

The procedure depends on whether the driver is pressing the brake pedal at the moment terminal 15 is switched off or not.

If the driver is pressing the brake pedal, the brake servo remains fully available for 60 seconds. In the following 120 seconds, the

brake servo is then reduced until it is fully switched off.

If the driver is not pressing the brake pedal, the brake servo remains fully available for 60 seconds and is then switched off.

System behaviour in the event of a fault

If the electromechanical brake servo fails, the ESC steps in to generate the brake pressure required. The brake pressure generated

by the driver’s pedal application is boosted accordingly. This condition is shown by the yellow warning lamp.

If the ESC is also not available, other functions in addition to the brake servo will not be available. The loss of the electronic brake

pressure distribution is particularly critical here, as this can lead to the rear axle being “overbraked” with a corresponding loss of

stability. For this reason, this condition is indicated by the red brake warning lamp and a driver message.

Service operations

The electromechanical brake servo must be replaced as a complete module. There is no provision for separating the mechanical

unit and the control unit in after-sales service. The Guided Function “0023 – Replace control unit” must be started before the part

is replaced. After the control unit has been coded online, a functional check (0023 - Brake booster / function test) is performed as

part of this function. If necessary (if the pressure check performed as part of the functional check returns a negative result), the

brake system must be bled according to the specifications in the Workshop Manual

The functional check should then be repeated. If the pressure test returns a negative result again, the Guided Functions “023 –

eBKV bleed brakes” and”003 – Service bleeding” must be performed. The final check is carried out in a concluding functional check.

This functional check verifies that the brake pedal is in the correct position (zero position) when it is not pressed. Pressure is then

built up actively, the position of the input rod is checked by the pedal travel sensor and the brake pressure level reached is checked

by the pressure sensor for the pressure in the ESC hydraulic unit.

ESC 9.2

Overview

The ESC of generation 9.2 is used on the Audi e-tron GT. The control unit and the hydraulic unit are combined as one unit. As in

various other Audi models (A6, A7, A8, Q7, Q8), a 6-piston pump (3 pistons per brake circuit) generates the necessary brake pres-

sure. The benefits of this design are that pressure can be generated more quickly, the pressure curves remain consistent, and the

acoustics are improved (fewer noises).

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ABS control unit J104

The control unit is connected to both FlexRay channels (A and B). The control unit processes the following main input signals:

›

Wheel speeds – the wheel speed senders are connected directly via discrete wires

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›

Longitudinal acceleration, lateral acceleration and yaw rate – via FlexRay from airbag control unit

Brake pressure – internal wiring to three pressure sensors integrated in the hydraulic unit

Steering angle – via FlexRay from steering angle sender G85 (part of steering column electronics control unit J527)

Motor torques – via FlexRay from motor control unit J623

On the basis of the data received, the control unit determines the wheel slip values in relation to the relevant driving state. If it

detects that regulation is required, it activates the control elements (solenoid valves and electric motor for pump units). It also

triggers the driver information displays required.

The software for activating the electromechanical parking brake is also included in the control unit.

Reference

For further information, please refer to SSP 475 "Audi ESC systems".

A new feature is a refresh routine to maintain the friction contact between the brake pad and the brake disc and prevent corrosion,

even when the vehicle is parked for a long time. The reason for this is the relatively low amount of time that the service brakes are

used for. Thanks to the use of recuperation to decelerate the vehicle, a mere 20 % of braking procedures now use the service

brakes, on average. The refresh routine is activated automatically after the vehicle has been stationary for at least six hours. In this

situation, the recuperation is temporarily deactivated in the next driving cycle and the service brakes are activated instead. Active

brake pressure is generated by the ESC to do this for as long as it takes to generate a defined amount of braking energy.

Hydraulic unit

As on other Audi models with ACC/adaptive cruise assist, the hydraulic unit contains six pump units, the electric motor for the

pump drive, the solenoid valves/switching valves, reservoirs and three pressure sensors. The construction and functions/switching

positions of the valves for the functions to generate, maintain and dissipate pressure fundamentally correspond to those of the

systems already in use. Large reservoirs ensure that pressure is dissipated very quickly in the first start-up phase of the return flow

pump.

Reference

For further information, please refer to SSP 475 "Audi ESC systems".

A pressure sensor permanently measures the pressure in the system (at the brake master cylinder output/the input of the hydraulic

unit). The pressure in the brake circuits (one on each axle) is measured by two additional sensors. As a result, it is possible to regu-

late the pressures at the wheel brakes very precisely so that brake blending can be achieved without the driver noticing the transi-

tions.

Operation and driver information

The ESC can be switched off by holding the corresponding button in the centre console for more than three seconds. This deacti-

vates traction control inputs and braking interventions on individual wheels. The system remains switched off during the current

terminal 15 cycle or until it is reactivated when the button is pressed again. The driver is informed of the deactivation via a message

on the display and the activation of the ESC OFF symbol.

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If system faults or malfunctions of certain other systems (e.g. adaptive air suspension, four-wheel drive, axle differential lock) are

diagnosed while the ESC is deactivated, the ESC is reactivated. This cannot be overridden. The ESC is switched on automatically ev-

ery time the drive system is switched on (terminal 15 on).

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The warning lamps for ABS/EDL, ESC, brakes, brake pad wear and parking brake (sometimes in conjunction with driver messages)

are activated by ABS control unit J104.

Wheel speed senders

Active Hall senders are used which can also detect the direction of travel. The senders are directly connected to control unit J104 via

two wires each. One wire is for power supply, the other is the signal wire. The earth connection is achieved by the bolted connection

between the sender and the wheel bearing housing/hub carrier. The sender module contains an electronic switch which converts

the analogue sensor signals into digital signals. Current signals are transmitted to the control unit. In addition to the frequency

(speed), they also include the direction of rotation, whether the vehicle is stationary, and the size of the air gap between the sensor

and the impulse ring. The size of the air gap is an important criterion for system diagnosis. If the vehicle’s drive system is activated

(terminal 15 on), the sensors are briefly supplied with current (self-test performed). The senders are supplied with power when the

drive system is activated; the power supply remains in place until the vehicle comes to a stop or the drive system is deactivated.

Magnetised impulse rings are integrated in the wheel bearing seals as impulse senders (48 north/south poles).

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Electromechanical parking brake (EPB)

Overview

A drum brake is used for the electromechanical parking brake on an Audi model for the first time on the Audi e-tron GT. The brake

system is a duo-servo brake system. The main benefit of this design is the identical braking effect when the vehicle is travelling

forwards or backwards. The inner end faces of the brake disc hubs provide the friction surfaces for the brake pads. The parking

brake and the service brakes are two separate systems. As is usual on Audi models, the electromechanical parking brake is operated

via a button in the centre console. The activation and regulation software is integrated in ABS control unit J104.

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Design and function

The brake shoes support themselves on one side against one of the actuator’s two thrust pieces On the other side, they make con-

tact with the adjustment mechanism on both sides. Two extension springs hold them in this position. The adjustment mechanism

is in a floating bearing arrangement and moves longitudinally. When forces are applied from the side by the brake shoes, the posi-

tion of the adjustment mechanism changes (longitudinal adjustment) depending on the amount of force applied. This technical

design achieves a duo-servo function. The servo function (self-boosting) results when, after being operated by the actuator’s thrust

piece, the brake shoe in this area first makes contact with the drum and, when it does so, applies a force (pressure) to the adjust-

ment mechanism at its other bearing position. The adjustment mechanism is moved towards the other brake shoe, which causes

this brake shoe to make contact with the brake drum. Both brake shoes are therefore the leading brake shoes for the brake drum. If

the brake shoes are mounted in a bearing arrangement on an adjustment mechanism which is fixed in position, there is no self-

boosting; one brake shoe leads and the other trails. The duo-servo function is achieved in that the actuator’s thrust pieces operate

both brake shoes. This means that the servo function is effective in both directions of travel (forwards and backwards).

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116

When the parking brake is engaged, both thrust pieces are moved outwards against the brake shoes. When it is released, the thrust

pieces move inwards towards each other. When the parking brake is released, the brake shoes centralise themselves automatically

thanks to their floating bearing arrangement in the area of the adjustment mechanism. To determine the exact position of the

thrust pieces, the rotational movement of the electric motor is determined by an internal sensor. Two separate wires transmit the

sensor signal to ABS control unit J104 and two additional wires are used to activate the electric motor.

Operation and driver information

Engaging the parking brake

On the Audi e-tron GT, the parking brake is again activated by the electromechanical parking brake button E538 in the centre con-

sole. As on all Audi models, the activated electromechanical parking brake is indicated by a parking brake symbol on the display.

Transmission position P (parking lock) is activated automatically when the parking brake is engaged with the vehicle stationary.

The parking brake can be activated at speeds < approx. 2 km/h. In this case, the vehicle is brought to a standstill by the parking

brake, and the parking lock is then only activated when the vehicle is stationary.

Releasing the parking brake

The parking brake is automatically released when the drive system is activated (transmission position D or R selected) and the ac-

celerator pedal is pressed. For this to happen, the driver's door must be closed and the driver's seat belt must be buckled. If the

vehicle is on a gradient of more than five degrees, it only moves off when the drive torque is sufficient to prevent the vehicle from

rolling back in the other direction.

Engaging and disengaging independently of the parking lock

The parking brake can also be manually engaged and disengaged independently of the parking lock when the vehicle is stationary

via a setting in the MMI.

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Emergency braking function

As on other Audi models, the electromechanical parking brake on the Audi e-tron GT can also be used for emergency braking in

dangerous situations. The vehicle must be travelling at a speed of > approx. 3.5 km/h to do this. The button must remain pressed

for the intended duration of the braking procedure and the accelerator pedal must not be pressed. An additional acoustic warning

signal is activated for the duration of the braking procedure.

Engaging manually

The condition for the functions described is that there is at least one valid wheel speed signal per axle. If this condition is not met,

the parking brake can still be engaged to park the vehicle. To do this, the switch must be operated for longer than 10 seconds with

terminal 15 switched off.

Additional functions

Automatic re-tensioning

To ensure that a defined retaining force is provided, the system is re-tensioned on parked vehicles after they have been stationary

for a specified period.

Automatic detection of brake test dynamometer

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If the wheels on one axle are stationary and those on the other axle are turning, the system detects that a test is taking place and

switches to the corresponding mode. If the wheels on the front axle are being driven by the roller, the parking brake is engaged. If

the wheels on the rear axle are being driven, the parking brake remains disengaged. This allows the service brakes to be tested as

usual. The electromechanical parking brake test corresponds to the emergency braking procedure.

Integration of hydraulic brake system in vehicle’s recuperation system

A braking procedure initiated by the driver can be achieved 100 % hydraulically, 100 % electrically or using a mix of the vehicle’s

hydraulic and electric braking power. The main conditions for recuperation are the ability of the battery to take in electric energy, a

dynamic driving state suitable for recuperation and a suitable vehicle speed. As a result, the system predominantly generates hy-

draulic brake pressure in corners as it is more likely that stabilising brake inputs (ESC regulation) will be needed. Regulation on

specific wheels can only be performed by the hydraulic brake system. Even if each wheel were driven by a separate electric motor,

the regulation of the electric motors would not be fast enough. Hydraulic brake pressure is also generated under braking at low

vehicle speeds in addition to recuperation. This ensures that the vehicle can be brought to a standstill safely. Autonomous braking

procedures (e.g. by the adaptive cruise assist, stop and go) are also supported by the ESC in conjunction with the electromechanical

brake servo. If braking procedures are required by/for assist systems where there is a certain level of danger potential (e.g. in

emergency braking procedures), any recuperation currently in progress is switched to a fully hydraulic braking procedure.

To ensure that the battery has a good level of charge and by extension a large range, the system recuperates energy as often as

possible. This also means that braking procedures with low to medium vehicle decelerations (up to approx. 3 m/s²) are usually per-

formed electrically. The driver will not be able to tell whether the braking procedure which he/she has initiated is being implemen-

ted electrically, hydraulically or as a mix of the two.

The decision as to which system contributes to what extent to providing the necessary braking torque is complex. Running gear

control unit J775, ABS control unit J104 and motor control unit J623 are primarily involved. The motor control unit permanently

transmits information on the current maximum recuperation capacity/braking power to the ABS control unit. If the driver presses

the brake pedal or an assist system (e.g. adaptive cruise assist) requests braking deceleration, the ABS control unit determines

whether the braking procedure required can be performed fully electrically via recuperation or whether additional hydraulic braking

power needs to be provided. It transmits the specified generator torque to the motor control unit. This is the amount of braking

power required from recuperation. At the same time, it sends a message to the running gear control unit with the calculated “ide-

al” distribution of the braking torque on the front and rear axle. As the running gear control unit is continuously determining the

current dynamic driving state, it coordinates the transition between acceleration and overrun recuperation phases and recuperation

distribution. It sends a specification for the torque distribution to the motor control unit, which then activates the power electron-

ics of the electric drive motors accordingly. The electromechanical brake servo works together with the ABS control unit and the

ESC hydraulic unit if hydraulic brake pressure also needs to be generated. If brake regulation procedures are required during an

active recuperation phase, the ABS control unit can, in the same way, initiate a reduction in recuperation or end it completely. At

the same time, the system generates hydraulic brake pressure which can be used (if hydraulic brake pressure has not already been

generated) to initiate regulation procedures for individual wheels.

As the proportion of hydraulic braking procedures performed by the service brakes is significantly lower in normal usage than on

vehicles with conventional drive systems, the hydraulic brake system is activated in certain situations even though an electric brak-

ing procedure using recuperation would also have been possible. If the vehicle has been stationary for a longer period (> 6 hours),

the first braking procedures are made hydraulically by the service brakes.

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Service operations

The diagnostic address is “0003 - Brake Electronics - J104”.

The entire module must be replaced if necessary. Replacing control unit J104 separately is not possible.

After the control unit has been coded online, the initial activation of the parking brake must be performed. This includes the follow-

ing three basic settings:

›

Adjust parking brake:

Adjusting the parking brake is necessary after removing/installing or replacing the brake shoes. At the start, the mechanic is

informed by the program that this basic setting is not necessary if this has not been done. After activating the basic setting, the

parking brake is automatically opened fully. The mechanic is then asked to set the correct clearance between the brake pads and

the brake drum according to the specifications in the Workshop Manual. This is performed at the adjustment mechanism. The

parking brake is subsequently closed.

Break in parking brake:

This basic setting is not required on the optional ceramic brake system. Breaking in the parking brake must only be performed

after the brake shoes have been removed/installed or replaced. At the start, the mechanic is informed by the program that this

basic setting is not necessary if this has not been done. A distance defined by the control unit (approx. 180 m) must be driven at

a low speed (approx. 15 - 20 km/h). Refer to information on vehicle diagnostic tester. During this, the brake shoes make contact

with the drum to adjust the friction surfaces. The vehicle diagnostic tester shows the distance remaining until the full distance

has been covered. We recommend that you do not perform this function on public roads.

Calibrate parking brake:

›

During calibration, the parking brake is opened fully and then closed as far as the clearance. The maximum opening position is

then stored in the control unit. A table with the currently set actual clearance value and the tolerance range of the specified

value is shown at the end of the calibration routine. If the actual value is not in the tolerance range specified, activation must be

performed again.

After the ABS/ESC module has been installed successfully, it must be ensured that the brake lines have been connected at the cor-

rect positions on the ESC hydraulic unit. Final control diagnosis “0003 – Hydraulic valve interchange check” in the vehicle diagnostic

tester can be used to do this. The procedure corresponds to that of other Audi models.

After the conventional bleeding procedure, the ESC hydraulic unit must be specially bled using the new function “0003 – Service

bleeding”. In this program, valves are activated in a defined manner to vent any air out of the hydraulic unit. A second mechanic,

who should press the brake pedal as requested by the diagnostic tester, is required to do this.

The Guided Function “0003 - Remove brake pads” is used to remove/install or replace the electromechanical parking brake’s brake

pads and the rear brake discs. The parking brake is fully opened in this process. Removal and installation can then be performed

according to the instructions in the Workshop Manual. After the mechanic has confirmed that the installation work has been per-

formed, the program closes the brake. After removing/installing or replacing the electromechanical parking brake’s brake pads,

the system must be activated as described above.

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The brake system is bled with regular brake bleeding equipment from the workshop equipment program. Four brake calipers with

two bleeder connections each are used for the first time on an Audi model.

After the brake discs and/or brake pads of the service brakes are replaced, the function “Break in service brakes” must be activated

on the vehicle diagnostic tester. After successful activation, the function will be performed in the background (without the vehicle

diagnostic tester connected) during the next driving cycles. The function will be continued when a new driving cycle is started if

defined conditions are met. During the routine, recuperation procedures are temporarily deactivated and the vehicle is decelerated

using the service brakes. In the following driving cycles, a defined amount of braking energy is generated and used to bed in the

brake pads and brake disc friction rings. Once the necessary braking power has been generated, the function is deactivated auto-

matically and the vehicle once again prioritises deceleration via recuperation.

Final control diagnosis can be used to check the function of the hydraulic pump, the warning lamps, the brake lights and the sound

boxes (acoustic signal).

Wheels and tires, tire pressure monitoring

The Audi e-tron GT comes with 19" forged aluminum wheels as standard equipment. 19" to 21" wheels are available as optional

extras. The RS e‑tron GT has 20” cast aluminum wheels as standard equipment. 20” or 21” wheels are available as optional extras.

Both models have reduced rolling resistance summer tires as standard equipment (distance tires). These tires are also available for

the optional 19” and 20” wheels. Summer tires designed for sporty handling (performance tires) are also available as optional

equipment for the 21” wheels. All the wheels offered can be fitted with all-season tires if desired. Winter tires and snow chains can

be used on all 19” and 20” wheels.

Depending on the market, the vehicle has the TMS breakdown set or a temporary spare wheel. A jack is included if the vehicle is

equipped with a temporary spare wheel. The Tire Mobility System (TMS) and the temporary spare wheel may be offered as

optional equipment on a market-specific basis.

Note

The offer structure in certain markets may differ from the one shown here.

Standard wheels

Optional wheels

Forged aluminum wheel

8.0J x 19 (FA)

Forged aluminum wheel

9.5J x 21 (FA)

Standard wheel for Audi e-

tron GT

Forged aluminum wheel

8.0J x 19 (FA)

225/55 R19

265/35 R21

10.0J x 19 (RA)

11.5J x 21 (RA)

305/30 R21

225/55 R19

275/45 R19

10.0J x 19 (RA)

275/45 R19

For Audi e-tron GT only

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Standard wheels

Optional wheels

Standard wheel for RS e-tron GT Cast aluminum wheel

Forged aluminum wheel

9.5J x 21 (FA)

Optional for Audi e-tron GT Cast

aluminum wheel

9.0J x 20 (FA)

245/45 R20

11J x 20 (RA)

285/40 R20

265/35 R21

11.5J x 21 (RA)

305/30 R21

245/45 R20

11J x 20 (RA)

285/40 R20

Cast aluminum wheel

9.0J x 20 (FA)

245/45 R20

Forged aluminum wheel

9.5J x 21 (FA)

Cast aluminum wheel

9.5J x 21 (FA)

265/35 R21

11.5J x 21 (RA)

305/30 R21

11J x 20 (RA)

11.5J x 21 (RA)

305/30 R21

285/40 R20

(FA) = front axle

(RA) = rear axle

Wheels 5, 6, 7, 8 and 9 in the table are fitted with aero blades which reduce the air resistance of the rotating wheels. The blades

are made of high-quality plastic and are bolted to the wheel spokes. Repair kits to replace defective blades are available in service.

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The third generation of the Tire Pressure Monitoring System is standard equipment. The system has the same construction

and works in the same way as the system in the Audi Q7 (type 4M).

The antenna is integrated in the control unit, and the module is fitted on the rear axle subframe, as on the Q7 and Q8.

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Running gear for Your Audi RS E Tron Gt 4 Door First Generation (2021-2026)

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