2004 PORSCHE 911 GT3 tire type

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

Temperature A,8,C

The temperature gradesareA(the highest), Band
C, representing thetire's resistance tothe gener-
ation ofheat anditsability todissipate heatwhen
tested undercontrolled conditions onaspecified
indoor laboratory testwheel.
Sustained hightemperatures cancause themate-
rial ofthe tire todegenerate andreduce tirelife,
and excessive temperature canlead tosudden
tire failure.
The grade Ccorresponds toalevel ofperfor-
mance whichallpassenger cartires must meet
under theFederal MotorVehicle SafetyStandard

No. 109.

Grades Band Arepresent higherlevelsofperfor-
mance onthe laboratory testwheel thanthemini-
mum required bylaw.

A
Warning!

The temperature gradeforthis tireisestablished
for atire that isproperly inflatedandnotoverload-

ed.

Excessive speed,underinflation, orexcessive
loading, eitherseparately orincombination, can
cause heatbuildup andpossible tirefailure.
Tire
pressures

A
Warning!
Incorrect tirepressure causesincreased tire
wear andadversely affectsroadhandling.

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Always useanaccurate tirepressure gauge
when checking inflationpressures.

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Donot exceed themaximum tirepressure list-
ed onthe tire sidewall.
Please observe thechapter "VEHICLE IDENTI-
FICATION, TECHNICAL DATA"onPage 179.

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Cold tireinflation pressure means:alltires
must becold, ambient temperature maximum
68°F (20°C), whenadjusting theinflation pres-
sure.
Avoid sunlight strikingthetires before measur-
ing cold pressures, sincethepressures would
rise from temperature influence.

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Valve capsprotect thevalve fromdustand
dirt, andthus from leakage.
Always screwcapstightly down.
Replace missingcapsimmediately.

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Donot use commercially availablesealantor
tire inflating bottles.
Tire
traction

A
Warning!
When driving onwet orslushy roads,a
wedge ofwater maybuild upbetween the
tires andtheroad. Thisphenomenon is
known as"hydroplane" andmay cause par-
tial orcomplete lossoftraction, vehicle
control orstopping ability.
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Reduce speedonwet surface toprevent this.

Tire life

Tire lifedepends onvarious factors, i.e., road
surfaces, trafficandweather conditions, driving
habits, typeoftires andtirecare.

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Inspect yourtires forwear anddamage before
driving off.Ifyou notice uneven orsubstantial
wear, wheels mightneedalignment ortires
should bebalanced orreplaced.
Practical Tips,Emergency Service

Tiredamage, puncture

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Check tiresforimbedded material,cuts,punc-
tures, cracks andbulges (sidewall)before
driving off.
In case oftire damage, whereitis uncertain
whether thereisabreak inthe plywith allits con-
sequences ortire damage causedbythermal or
mechanical overloading duetoloss ofpressure or
any other priordamage, werecommend thatthe
tire bereplaced forsafety reasons.
If one faulty tireisreplaced itshould benoted that
the difference intread depth onone axle must not
exceed 30
%.

Handling inconsistencies mayresult.

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Perform avisual inspection ifnecessary.
Tire replacements
If in doubt, contact yourPorsche dealeror
Porsche Importer ofyour country.
Use only tiremakes andtypes tested byPorsche.

If you donot use aPorsche recommended
replacement tire,make surethatyou
purchase yournewtires from areputable
tire dealer andthat thedealer complies with
all manufacturers warningsforthose tires.
Only tires withthesame make andwith the
same specification code(e.g."NO", "Nl"... )
can bemounted. Before
mounting newtires, check withyour
Porsche dealeraboutthecurrent release
status.
Use tires with"ZR" quality standards.
There
are currently nostandards concerning tire
strength atspeeds above150mph (240 kmjh).
Tires should bereplaced noless than onone axle
at the time.
Only tires ofthe same makeandtype must be
used. Mixed tiresarenotpermissible.
Initially, newtires donot have theirfulltraction.
You should therefore driveatmoderate speeds
during thefirst 60-120 miles (100-200 km).
If new tires areinstalled onlyonone axle, anotice-
able change inhandling occursduetothe different
tread depth ofthe other tires.
This happens especially ifonly reartires arere-
placed. However, thiscondition disappears asthe
new tires arebroken in.

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Please adjustyourdriving styleaccordingly.
Installation ofnew tires should onlybedone bya
qualified tiretechnician.
Valves

Rubber valvestems mustbereplaced everytime
a tire isreplaced.
For metal valves, theinstallation andreplacement
instructions mustbeobserved.
Use only genuine Porsche metalvalves.
Parking atthe curb

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Warning!
Hard impacts againstcurbs(ortraffic
islands) aredangerous andmay cause hid-
den tiredamage whichisnot noticeable until
later. Suchdamage canresult inaccidents
at high speeds causing severepersonal inju-

ry.

Depending onthe force ofimpact, theedge
of the rim can also bedamaged.

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Ifyou areindoubt, havethewheel checked by
an expert, particularly ifyou suspect damage
on the inside.

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Ifyou must driveoveracurb orother obstacle,
drive slowly andatan obtuse angle.Exercise
care when parking alongcurbs.
Practical Tips,Emergency Service

Transmission
1 st gear
2nd gear
3rd gear
4th gear
5th gear
6th gear
Reverse
Final drive ratio

lire Pressures forcold tires
3.82:
1

2.15:1 1.56 :1
1.21 :1

1.00 :1

0.85: 1

2.86: 1

3.44:1

Summer tiresandsnow tires
Front 32psi(2.2 bar)overpressure
Rear 39psi (2.7 bar)overpressure
These tirepressures applyonlytothe tire makes andtypes approved byPorsche.
Please observe thechapter "TIRESIWHEELS" onPage 141.
TechnicalData

Tires,Rims,Tracks

Tire RimRimoffset
Track
Summer tires
front
235/40ZR18(91 Y)
8.5Jx 18 H2 40mm
58.6in/1488 mm
rear 295/30ZR18(98Y)
11Jx 18 H2
63mm 58.6in/1488 mm

Snow tires
front
225/40R18 92V M+S XL 8Jx 18 H2
50mm 57.8in/1468 mm
rear 265/35R18 97V M+S XL
*

10Jx18H2 65mm 58.4in/1484 mm
The load capacity coefficient (e.g."92") andmaximum speedcodeletter (e.g."V")areminimum requirements.

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Warning!
Installation ofsizes notauthorized by
Porsche mayhave adangerous effecton
the driving stability andcould result in
severe personal injuryordeath.
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Before mounting newtires, check withyour
Porsche dealeraboutthecurrent release
status.

Tire andrimsizes
Extensive testsareperformed beforespecific tiresandwheels areapproved byPorsche. YourPorsche dealerhasinfor-
mation aboutapproved tiresandwheels andishappy toassist you.
If aftermarket tiresand/or wheels areinstalled whicharenotapproved byPorsche, thevehicle's roadability andhandling
characteristics mightbeimpaired. SincePorsche hasnodata onsuch combinations, Porschecannotstandbehind the
safety ordurability ofthese aftermarket combinations.

Snow chains
Canbemounted onlyonthe rear wheels;
maximum speed30mph/50 km/h.

Use only Porsche authorized fine-linkcross-type oredge chains.

Snow chain clearance canbeguaranteed onlyonthe tire
+
rim combination marked*.

Technical Data