OperationoftheABSsystem
Awheelspeedsensorismountedtoeachofthe
fourwheels.Ifwheellock-upofeitherofthe
frontwheelsortherearwheelsissensedduring
braking,thebrakepressureisadjustedautomat-
icallyuntilthewheelnolongerslips.Thebrake
pressureisregulatedforeachfrontwheelindi-
viduallyandforbothoftherearwheels
together.
Onaroadsurfacewhichisslipperyononlyone
side,therearwheelwhichisbrakingontheslip-
perysurfacedeterminesthebrakepressure
whichwillbeappliedequallytobothrearwheels.
Thisensuresthatdirectionalstabilityismain-
tained.However,ifbrakingforcesapproachthe
wheellock-uppointforallwheels(panicbraking)
theABSsystemwillintervenetoprovidearapid
rythmicbraking.
TheproperoperationofABSisperceivedbythe
driverasapulsatingbrakepedalinconjunction
withaudiblenoiseandperhapssomevibration.
I>Ifyouexperiencethesesensationswhiledriv-
ingoraroadsurfacewithquestionabletrac-
tion,reducevehiclespeedappropriateforthe
prevailingroadconditions.
Thefunctionalreadinessofallthemainelectrical
componentsoftheABSischeckedbyanelec-
tronicmonitoringsystembothbeforeandwhile
youdrive.
8
WarninglightUSA
@
WarninglightCanada
WhentheignitionisswitchedontheABSwarn-
inglightwilllightupwhilethesystemiselec-
tronicallyinterrogatedandgoesoutwhenthe
engineisstartedifthecheckisnotyetcom-
plete.
IftheABSwarninglampfailstogoout,thisindi-
catesthatABShasbeendeactivatedduetoa
fault.Ifthewarninglightsintheinstrumentpanel
andon-boardcomputerlightupwhileyouare
driving,thisindicatesthatafaulthasoccurred.
Inbothcases,normalbraking,asinvehicles
withoutABS,isstillretained.
TheABSsystemshould,however,beexamined
atanauthorizedPorschedealerimmediatelyto
preventtheoccurrenceoffurtherfaults.
I>IftheABSsystembecomesinoperative,take
yourvehicletoyourauthorizedPorsche
dealerimmediately.
/!\Warning!
ThecontrolunitoftheABSbrakesystemis
setforstandardtiresize.Ifnon-standard
tiresareinstalled,thecontrolunitmaymis-
interpretthespeedofthevehicle,because
ofthevariantdataitreceivesfromthesen-
sorsontheaxles.
I>Useonlytiremakesandtypestestedby
Porsche.
Controls,Instruments
57
911Carrera
45
TireRim
Summertires
front
225/40ZR188Jx18H2
rear
295/30ZR1811Jx18H2
or
rear
295/30ZR1811Jx18H2
Snowtires
front
225/40R1888HM+S8Jx18H2
rear
*265/35R1893HM+S10Jx18H2
RimoffsetTrack
50mm57.9in./1472mm
45mm60.2in./1528mm
63mm(onlywith17mm
spacer
ring)
60.1in./1526mm
50mm
47mm
57.9in./1472mm
60.0in./1524mm
Theloadcapacitycoefficient(e.g."88")andmaximumspeedcodeletter(e.g."H")areminimumrequirements.
A
Warning!
Installationofsizesnotauthorizedby
Porschemayhaveadangerouseffecton
thedrivingstabilityandcouldresultin
severepersonalinjuryordeath.
[>
Beforemountingnewtires,checkwithyour
Porschedealeraboutthecurrentrelease
status.
[>[>[>
TechnicalData
247
Tire
andrimsizesExtensivetestsareperformedbeforespecifictiresandwheelsareapprovedbyPorsche.
YourPorschedealerhasinformationaboutapprovedtiresandwheelsandishappytoassistyou.
Ifaftermarkettiresand/orwheelsareinstalledwhicharenotapprovedbyPorsche,thevehicle'sroadabilityandhandling
characteristicsmightbeimpaired.SincePorschehasnodataonsuchcombinations,Porschecannotstandbehind
thesafetyordurabilityoftheseaftermarketcombinations.
SnowchainsCanbemountedonlyontherearwheels;maximumspeed30mph/50km/h,
UseonlyPorscheauthorizedfine-linkcross-typeoredgechains.
Snowchainclearancecanbeguaranteedonlyonthetire+rimcombinationmarked*,
Sparewheel911Carrera:T105/95R17high-pressuretireon3.5Jx17rim.
911Carrera4,Carrera4S:165/70R1692Pcollapsibletireon5.5Jx16rim.
Maximumspeed50mph/80km/h,Alwayscomplywiththeinstructionsinthechapter"Sparewheel",
248TechnicalData
