2004 PORSCHE 911 GT3 four wheel drive

Operation ofthe ABS system
A wheel speed sensor ismounted toeach ofthe
four wheels. Ifwheel lock-up ofeither ofthe front
wheels orthe rear wheels issensed duringbrak-
ing, thebrake pressure isadjusted automatically
until thewheel nolonger slips.Thebrake pressure
is regulated foreach frontwheel individually and
for both ofthe rear wheels together.
On aroad surface whichisslippery ononly one
side, therear wheel whichisbraking onthe slip-
pery surface determines thebrake pressure which
will beapplied equallytoboth rearwheels. Thisen-
sures thatdirectional stabilityismaintained. How-
ever, ifbraking forcesapproach thewheel lock-up
point forallwheels (panicbraking) theABS system
will intervene toprovide arapid rythmic braking.
The proper operation ofABS isperceived bythe
driver asapulsating brakepedalinconjunction
with audible noiseandperhaps somevibration.

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Ifyou experience thesesensations whiledriv-
ing oraroad surface withquestionable trac-
tion, reduce vehicle speedappropriate forthe
prevailing roadconditions.
The functional readinessofall the main electrical
components ofthe ABS ischecked byan
electronic monitoring systembothbefore and
while youdrive. •
Warning lightUSA
• Warning lightCanada
When theignition isswitched onthe ABS warning
light willlight upwhile thesystem iselectronically
interrogated andgoes outwhen theengine is
started ifthe check isnot yetcomplete.
If the ABS warning lampfailstogo out, thisindi-
cates thatABS hasbeen deactivated duetoa
fault. Ifthe warning lightsinthe instrument panel
and on-board computer lightupwhile youaredriv-
ing, this indicates thatafault hasoccurred. Inboth
cases, normal braking, asinvehicles withoutABS,
is still retained.
The ABS system should,however, beexamined at
an authorized Porschedealerimmediately topre-
vent theoccurrence offurther faults.

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Ifthe ABS system becomes inoperative, take
your vehicle toyour authorized Porschedealer
immediately.
A

Warning!
The control unitofthe ABS brake system is
set forstandard tiresize. Ifnon-standard
tires areinstalled, thecontrol unitmay mis-
interpret thespeed ofthe vehicle, because of
the variant dataitreceives fromthesensors
on the axles.

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Use only tiremakes andtypes tested by
Porsche.
Controls,Instruments

Wheelalignment, wheelbalancing

As aprecaution, havewheels withsummer tires
balanced
in
the spring, andthose withmud and
snow tiresbefore winter.
Unbalanced wheelsmayaffect carhandling and
tire life.
Only thespecified weightsmaybeused forwheel
balancing. Self-adhesive weightsmustnotcome intocontact
with cleaning agents,sincetheycould dropoff.
A wheel should always bebalanced afteratire re-
pair.
Uneven treadwearindicates wheelimbalance. In
this event, thevehicle shouldbechecked atan au-
thorized Porschedealer.

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Warning!
If, during ajourney, unevenrunning orvibra-
tions occur thatcould becaused bydamage
to tires orthe car, thespeed mustbere-
duced immediately, butwithout braking
sharply.
If you continue yourtripwithout havingthe
cause ofthe fault remedied, youmight lose
control ofyour vehicle whichcouldcause se-
vere personal injury.

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Stop thevehicle andcheck thetires.

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Ifno cause forthe fault canbefound, drive
carefully tothe nearest authorized Porsche
dealer.
Practical Tips,Emergency Service
Removing
andstoring tires

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After changing, adjusttirepressure andtorque
wheel boltsdiagonally to94 ftlb (130 Nm).
Please observe thechapter "CHANGING A
WHEEL" onPage 150.

Tires mustalways remain onthe same side
of the vehicle.

When wheels areremoved, thedirection ofrota-
tion andposition ofeach wheel should bemarked.

Example

FR (front right), FL,RRand RL.
Wheels mustalways befitted inaccordance with
their marking.
The preception thattiredurability andperfor-
mance areimmune tothe effects ofstorage and
age isunfounded.
Chemical additives, whichmaketherubber elas-
tic, lose their effectiveness inthe course oftime
and therubber becomes brittleandcracks.

Therefore, thetires should beinspected
from timetotime. Note

Under nocircumstances shouldtiresolder than6
years beused onyour Porsche.
The ageofthe tire can beobtained fromthe"DOT"
code number. If,for example, thelast four num-
bers read 1203, thenthetire was produced inthe
12th week of2003.

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Store tiresinacool anddryplace.

Snow tires

For abetter griponsnow andice,useradial M+S
tires withstuds.
Check withyour local Motor Vehicle Bureaufor
possible restrictions.

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Warning!
Risk ofloss ofcontrol anddamage tothe
vehicle aswell assevere personal injury.
The standard tiresprofile andrubber mix-
ture areoptimized forwet and drydriving
conditions, andmay notprove favorable for
snow conditions.

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Therefore installM+Stiresbefore driving in
such conditions.

Beforemounting snowtires, consult with
your Porsche dealer.Hehas thetechnical
information necessarytoadvise youon
wheel andtirecompatibility.

Snow tiresshould havethesame loadcapacity as
original equipment tiresandshould bemounted
on allfour wheels.
Snow tireswithstuds should berun atmoderate
speeds whennewinorder togive thestuds time
to settle.

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Warning!
Tires withbadly worntreads andstuds are
very dangerous andcould cause accidents
resulting insevere personal injuries.

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Make surethey arereplaced immediately.
Do not drive avehicle equipped withsnow tiresat
prolonged highspeed.
Snow tiresdonot have thesame degree oftrac-
tion ondry, wet orsnowfree roadsasanormal
tire. Furthermore, snowtireswear rapidly underthese
conditions.
Snow tiresdonot fulfill their purpose ifthe tread
depth isless than 5/32 in.(4mm).

Comply withallstate andlocal laws
governing snowtireand tread depth
requirements.
Snow
chains

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Caution!
Risk ofdamage tobody, axleorbrake com-
ponents.

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Fitsnow chains onlytothe rear wheels, and
only withthetire/rim combination listedinthe
Technical Data.
To ensure adequate clearance betweenchain
and body, Porsche recommends onlytheuse
of fine-link chainssuchasthose approved by
Porsche.

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Follow instructions issuedbythe supplier of
the chains.
Different statesandcountries havevarying statu-
tory requirements regardingmaximum speed.
Check withlocal authorities forpossible restric-
tions.

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Remove chainsassoon asthe roads arefree
of ice and snow.
Tire
designations

Due tonew speed andload ratings forradial tires,
new designations havecome intoforce forsnow
tires foryour Porsche.
The designation tobe used forZRtires ise.g.,
255/40 ZR17(Z
=
code letterforradial tiresfor
speeds above150mph (240 kmjhl.
Practical Tips,Emergency Service

Towing
Certain statestatutes andlocal ordinances prohib-

it
towing withachain, ropeoreven atow bar.
In addition, damagetoyour vehicle mayresult
from improper procedures.
Consult yourauthorized Porschedealerforde-
tails.

Vehicle towing

Flat bed towing isthe preferred typeoftowing to
be used onPorsche vehicles.
Under certain circumstances, wheelliftsmay be
used when thevehicle willnotroll.

The vehicle mustbetowed withallfour
wheels offthe ground, otherwise damageto
the vehicle mayresult.

Towing eye

The towing eyeiscontained inthe tool kit.

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Caution!
Risk ofdamage tothe vehicle.

'" Use thetowing eyeonly foranemergency to
remove thevehicle offthe road. Thetowing
eye isto be used onlytopull thevehicle onto
the flat bed, tractor ortowing aparatus ifthe
vehicle willrollfreely. Undernocircumstances
is the vehicle tobe secured usingthetowing
eye. '"
Never usethetowing eyetotow thisorany
other vehicle.

Front mounting

1. Carefully removetheplastic capbeside the
license platewithascrew driver.
2. Screw thetowing eyeintothehole.
Rear
mounting

1. Remove licenseplate.
2. Carefully removetheplastic capbetween the
bumpers withascrew driver.
3. Screw thetowing eyeintothehole.

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Practical Tips,Emergency Service
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