2008 AUDI S8 tire size

Driver inf ormation displ ay
In addit ion, a ll the values in the single-trip or the total -trip memory
can be de leted s imu ltaneously.
[ i ] Tips
All stored values will be lost if the vehicle battery is disconnected. •
MMI settings
Basic settings for the trip computer can be made in the
MM/.
Fig . 2 4 M MI di splay :
Trip com put er
S ett ing v alu es to ze ro
- Pressthe!CAR)function button.
- Select
S ystems in the CAR menu .
- Selec t
Instrum ent cluster.
- Selec t Trip compute r 1 or Trip comput er 2.
- Select Reset to delete all the values in the memory
=> fig. 24 .
Displaying and hiding dri ver inform ation
- Press the
I CAR) f unct ion butto n. - Selec
t
Syste m s in the CA R me nu.
- Select
Instrument clu ster .
- Select Trip computer 1 or Trip computer 2 .
-Select, for example, Fu el range On to tu rn on t he display
or
Off t o turn the display o ff.
All values in the s ingle -tr ip or the total -trip memory can be reset to
zero simultaneously in MMI. In addition you can de termine what
driving information from the trip computer shou ld be shown in the
ins trument cluster display. If one of the pieces of dr iver information
is turned
off, that driver information will not be shown in the display .
The informat ion wi ll continue to be calcu lated by the trip computer
and can be turned back
on at any time. •
Tire pressure monitoring system
General notes (l)
Each tire, including the spare {if provided), should be checked
monthly when co ld and in flated to the inflation pressure recom ­
mended by the vehicle manufacturer on the vehicle p lacard or tire
inf lation pressure labe l. (If your vehicle has tires of a different size
than the size indicated on the vehicle placard or tire inflation pres­
sure labe l, you should determine the proper tire inf lation pressure
for those
tires.!
As an added safety feature , your vehicle has been equipped with a
t ire pressure monitoring system {TPMS) that illuminates a low t ire
pressure telltale when one or more of your tires is significantly
under -inf lated. Accordingly, when the low t ire pressure te lltale i llu­
minates , you should stop and check your tires as soon as possible,
and inf late them to the proper pressure . Driving on a significantly
under-inf lated tire causes the tire to overheat and can lead to tire
~

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Tire chains
Where tire chains are mandatory on certain roads, this normally
also applies to vehicles with All Wheel
Drive:::::, page 342, "Snow
chains".
Replacing wheels/tires
Vehicles with All Wheel Drive must always have tires of the same
size . Also avoid tires with different tread depths. For details see
page :::::, page 336, "New tires and replacing tires and wheels".
Off-Road driving?
Your Audi does not have enough ground clearance to be used as an
off-road vehicle. It is therefore best to avoid rough tracks and
uneven terrain as much as possible. Also refer
to:::::, page 279.
& WARNING
Always adjust your driving to road and traffic conditions. Do not
let the extra safety afforded by All Wheel Drive tempt you into
taking extra risks.
• Although the All Wheel Drive is very effective, always
remember that braking capacity is limited by tire traction. You
should therefore not drive at excessive speeds on icy or slippery
road surfaces.
• On wet road surfaces, be careful not to drive too fast because
the front wheels could begin to slide on top of the water (aqua­ planing).
If this should occur, you will have no warning from a
sudden increase in engine speed as with a front-wheel drive
vehicle. Always drive at speeds which are suited to the road condi­
tions -risk of crash. •
Energy management
Starting ability is optimized
Energy management controls the distribution of electrical
energy and thus optimizes the availability of electrical
energy for starting the engine.
If a vehicle with a conventional energy system is not driven for a
long period of time, the battery is discharged by idling current
consumers (e.g . immobilizer) . In certain circumstances it can result
in there being insufficient energy available to start the engine.
Intelligent energy management in your vehicle handles the distribu­
tion of electrical energy. Starting ability is markedly improved and
the life of the battery is extended.
Basically, energy management consists of
battery diagnosis, idling
current management
and dynamic energy management.
Battery diagnosis
Battery diagnosis continuously determines the state of the battery.
Sensors determine battery voltage, battery current and battery
temperature. This determines the current state of charge and the
power of the battery .
Idling current management
Idling current management reduces energy consumption while the
vehicle is standing. With the ignition switched off, it controls the
energy supply to the various electrical components . Data from
battery diagnosis is considered.
Depending on the battery's state of charge, individual consumers
are gradually turned off to prevent excessive discharge of the
battery and thus maintain starting capability.
Dynamic energy management
While the vehicle is being driven , dynamic energy management
distributes the energy generated according to the needs of the indi -_,,,

Tires and wheels -
----------------
•
& WARNING (continued)
crashes and serious personal injuries . Have worn or damaged tires
replaced immediately.
• Tires age even if they are not being used and can fail suddenly,
especially at high speeds. Tires that are more than 6 years old can
only be used in an emergency and then with special care and at
low speed.
Glossary of tire and loading terminology
Accessory weight
means the combined weight (in excess of those standard items
which may be replaced) of automatic transmission, power steering,
power brakes, power windows, power seats, radio, and heater, to
the extent that these items are available as factory-installed equip­
ment (whether installed or not).
Aspect ratio means the ratio of the height to the width of the tire in percent.
Numb ers of 55 or lower indicate a low sidewall for improved
steering response and better overall handling on dry pavement.
Bead
means the part of the tire that is made of steel wires, wrapped or
reinforced by ply cords and that is shaped to fit the rim.
Bead separation
means a breakdown of the bond between components in the bead.
Cord
means the strands forming the plies in the tire.
& WARNING (continued)
• Never mount used tires on your vehicle if you are not sure of
their
"previous history." Old used tires may have been damaged
even though the damage cannot be seen that can lead to sudden
tire failure and loss of vehicle control.
• If you notice unusual vibration or if the vehicle pulls to one side
when driving, always stop as soon as it is safe to do so and check
the wheels and tires for damage.
•
Cold tire inflation pressure
means the tire pressure recommended by the vehicle manufacturer
for a tire of a designated size that has not been driven for more than
a couple of miles (kilometers) at low speeds in the three hour period
before the tire pressure is measured or adjusted.
Curb weight
means the weight of a motor vehicle with standard equipment
including the maximum capacity of fuel, oil, and coolant, air condi­
tioning and additional weight of optional equipment.
Extra load tire
means a tire design to operate at higher loads and at higher infla ­
tion pressures than the corresponding standard tire. Extra load tires
may be identified as
"XL", "xi", "EXTRA LOAD", or "RF" on the side ­
wall.
Gross Axle Weight Rating
("GAWR")
means the load-carrying capacity of a single axle system, measured
at the tire -ground interfaces.
Gross Vehicle Weight Rating
( " GVWR")
means the maximum total loaded weight of the vehicle.
Vehicle care

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Groove
means the space between two adjacent tread ribs.
L oa d r atin g (code)
means t he m aximum load that a t ire is rated to carry for a given
inf lation pressure . You may not find this information on a ll tires
because it is not required by law.
M ax imum l oad r ating
means t he load rating for a tire a t the maximum permissib le infla­
tion pressure for that tire.
Maximum l oaded v ehi cle wei ght
means the sum of:
(a) Curb weight
(b) Accessory weight
(c) Vehicle capaci ty weight, and
(d) Product ion options weight
M ax imum (p er mis sibl e) infl ati on pr essure
means the maximum cold i nflation pressure to wh ic h a t ire may be
inflated. Also cal led "maximum inflation pressure."
Normal occ upant we ight
means 150 lbs. (68 ki lograms) times the number of occupants
seated in the veh ic le up to the total seating capacity of your vehicle.
Oc cupant distributi on
means distribution of occupants in a vehicle .
Outer di ameter
means the overal l diameter of an inf lated new tire.
O verall width
means the linear distance between the exteriors of the sidewa lls of
an infla ted t ire, includ ing elevat ions due to labe ling, decorat ions, or
protective bands or ribs .
Ply
means a layer of rubber -coated para llel cords.
P rodu cti on opt ion s we ig ht
means the co mbined weight of those insta lled regular product ion
options weighing over 5 lbs. (2.3 kg) in excess of those standard
items which t hey replace, not previously considered in curb weight
or accessory weight, inc luding heavy duty brakes, ride levelers, roof
rack, heavy du ty bat tery, and special trim .
Rad ia l pl y tir e
means a pneumat ic t ire in wh ich t he ply cords that extend to the
beads are laid at substantially 90 degrees to the centerline of the
t read .
Recomm ended infl ation pres su re
see :::::> page 325, "Cold tire inflat ion pressure".
R einforc ed tir e
means a tire des ign to operate at higher loads and at higher infla­
tion pressures than the corresponding standard tire. Reinforced
t ires may be iden tified as
"XL", "xi", "EXTRA LOAD", or "RF" on the
sidewa ll.
Rim
means a metal support for a tire or a tire and tube assembly upon
whic h the t ire beads are seated.
Rim di ame ter
means nominal diameter of the bead seat. If you change your whee l
size, you wi ll have to purchase new tires to match the new rim diam ­
eter.
Rim siz e design ation
means rim diameter and width.
Rim w idth
means nominal distance between rim flanges .

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Occupant loading and distribution for vehicle normal load for various designated seating capacities Designated seating capacity , num­
ber of occupants
4
5
Cold tire inflation pressure
Vehicle no rmal load, number of
oc cupants
2
3
Occupant distribution in a normally
loaded vehicle
2 in front
2 in front, 1 in back seat
Tire pressure affects the overall handling, performance and safety of a vehicle.
Fig . 272 Tire pressure
label: located either on
driver's side B-pillar or
inside the fuel filler flap
llRE AND LOADING INFORMATION
T IRE SIZE COLO TIRE PRESS URE
FRONT -KPa, -PSI
REAR -KP a, -PSI
SPARE -KPa , -PSI \.~__., ::::::::;=~ ===..:;,;_. Fig. 273 Tire pressure
label
Maintaining proper tire pressure is one of the most important
things you can do to help avoid sudden tire failure. Underinflated
tires are a major cause of sudden tire failure. Keeping tires at the
right pressure is also important for safe and responsive vehicle
handling, traction, braking and load carrying.
Tire pressures are
particularly important when the vehicle is being driven at higher
speeds, and then especially when heavily loaded even within the
permissible load-carrying capacities approved for your vehicle.
The recommended tire pressures for your Audi depend on the kind
of tires on your vehicle and the number of passengers and/or
amount of luggage you will be transporting.
•
Tire pressure generally refers to the amount of air in a tire that it
needs it to do its job and safely carry the combined load of the entire
vehicle and its contents . Tire pressure is measured in kilopascals
(kPa), the international measuring unit and in pounds per square
inch (PSIJ. Tire pressure is based in part on the vehicle's design and
load limit
-the greatest amount of weight that the vehicle can carry
safely and the tire size. The proper tire pressure is frequently
referred to as the "recommended cold tire inflation pressure." Air in
the tires expands when the tire heats up because of internal friction
when it flexes in use. The tire pressure is higher when the tire has
warmed up than when it is "cold." It is the inflation pressure in a
"cold" tire that counts. Therefore, you should never let air out of a
warm tire to match "cold tire inflation pressure " recommendations .
The tires would then be underinflated and could fail suddenly. On
USA vehicles, the tire pressure label is located on the driver's
side 8-pillar . On Canada vehicles , the tire pressure label is located
either on the driver's side 8 -pillar or inside the fuel filler flap . The tire
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Engine Tire designation Tire pressure front Tire pressure rear
( displace-
normal load full load normal load
full load
ment in
liter)
condition al condition conditiona l condition
kPA PSI kPA PSI kPA PSI
12-cylinder
255/45 R18 99H All Season 36 250 38 260 32 220 32 220
6.0 Individual
255 /40 R19 100V XL All Season 41 280 4 1 280 36 250 36 250
rear seats
255/40 R19 100V
XL High Performance
36 2
50
38 260 3
2 220 32 2 20
275 /35 R20 102Y
XL High Performance 38 41 280 35 2 40 44 300
12 -cylinder 255 /45 R18 99H All Season 36 250 36 250 32 220 32 220
6 .0
255 /40 R19 100V XL All Season 4 1
280 4
1
280 36 250 36 250
255 /40 R19 100V
XL High Performance
36 250 36 250 32 2 20 32 220
275 /35 R20 102Y XL High Performance 38 260 4 1 280 35 240 44 300
XL = reinforced or extra load tire . It may also appear as xi , EXTRA LOAD , or RF on the tire sidewall .
al norma l load cond ition => page 328.
The co rrect tire pressure for the spare wheel is located on a label
either on the driver 's s ide 8-pillar or inside t he fue l fil ler flap.
Because technica l changes may be made to vehicle equipment
du ring t he mode l year, always co mpare the tire si ze desig nati on on
the tire pressure label on your vehicle with the tires on your vehicle .
M ake s ure t hat the tire si ze info rmat ion o n the ve hicle labe l is the
same as the size of the tires on the vehicle . T his is especial ly impor ­
t an t if t he vehicle bel ongs t o so me one e lse o r yo u boug ht the
vehic le with different rims/tires or you bought the vehicle as a previ ­
ously owned ve hicle.
Reme mber, you r safety and that of y our passengers a ls o depe nds
on making su re that load limits are not exceeded. Vehicle load
i nc ludes every body and everyt hin g in and o n th e veh icle . T hese load
limits are technically referred to as the vehicle's Gross Veh ic le
Weig ht Ratin g ("GVWR"). T he Gro ss Axle Weigh t Ra tin g ("GAWR") is
the maximum load that can be applied at each of the vehicle's two axles
. The Gross Vehic le We ight Rating and the Gross Axle Weight
Rating are l isted on the safety compl iance sticker labe l located
either on the driver's side 8 -pillar or on the inside of the fuel filler
fl ap . T he t ire p ressure label on you r A ud i lists t he m axi mum
combined weight of a ll of the occupants and luggage or other cargo
th at the v ehicle can carry . Fo r the locati on of the t ire press ure la be l
=> page 328, fig . 27 2.
& WARNING
Overloading a vehicle can cause loss of vehicle control , a crash or
other accident, serious per sonal injury , and even death .
• Carrying more weight than your vehicle was designed to carry
will prevent the vehicle from handling properly and increase the risk of a loss of vehicle control. ...,

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Incorrect wheel alignment
Incorrect wheel alignment can cause excess ive tire wea r, impairi ng
the safety of the vehic le. If tires show excessive wear, have the
whee l alignment c hecked by an au th o rize d Audi deale r or qualifie d
wo rkshop.
All Wheel Drive
Vehicles with quattro® must always have tires of the same size, construc tion and tread type. F or details see
~ p age 273 .
& WARNING
Sudden tire failure can lead to los s of control, a crash and serious
personal injury !
• Never drive a vehicle when the tread on any tire is worn down
to the wear indi cators .
• Worn tires are a safety hazard, they do not grip well on wet
roads and increase your risk of "hydroplaning " and loss of control.
• Always keep chemicals that can cause tire damage , such as
grease, oil , gasoline and brake fluid aw ay from tires .
• Tires age even if they are not being used and can fail suddenly ,
especially at high speeds. Tires that are more than 6 years old can
only be used in an emergency and then with special care and at
lower speed s.
• Never mount used tires on your vehicle if you are not sure of
their "previous history." Old used tires may have been damaged
even though the damage cannot be seen that can lead to sudden
tire failure and los s of veh icle control. •
New tires and replacing tires and wheels
N ew t ires and wheels h ave t o be broke n in.
Fig . 2 76 T ir e specification code s on the sidewall of a tire
No .
G)
0
©
©
©
©
Description
Passenger car tire (where applicable)
Nominal width of tire in millimeters
Ratio of height to width (aspect ratio)
Radial
Rim diameter code
L o ad in dex and s peed rat ing

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•
• T he batt ery inside of the tire pressure sensor has a l imited
s er vice l ife.
• Al ways drive with the va lve stem ca ps sec ure ly m ounted. We
r ec om mend u sin g fa ctor y in sta lle d v alv e stem caps. Ask your autho­
rized Audi d ealer to replac e lost valve stem caps .
T he in stalla tio n of replacement ti res with steel cord body plies i n
th e tire s id ewal l may cause malfunct ion of the tire pressure moni ­
toring sy ste m, and is not recommended (c ord mate ria l infor mation
i n mo lded on the tire s idewa ll).
Al ways check your tir e pressure monitor ing system indicator after
r eplac ing on e o r m ore tire s on y our vehi cle. If the tire pressu re
monitorin g system indicator flashes, or is on, your system is not
w orki ng pr ope rly. You r rep lace ment tir e mi ght be in co m pati ble w ith
your t ire pr essure monitoring system, or some component of the
t ir e pr ess ure m oni to ring sys te m m ay be damaged .
& WARNING
• Using incorrect or unmatched tires and / or wheels or improper
tire and wheel combinations can lead to loss of control , collision
and serious personal injury .
• Always use tires , rims and wheel bolts that meet the specifica­
tions of original factory -installed tires or other combinations that
have been specifically approved by the vehi cle manufacturer .
• Tires age even if they are not being used and can fail suddenly,
espe cially at high speeds . Tires that are more than 6 years old can
only be used in an emergency and then with special care and at
lower speeds .
• Never mount used tires on your vehicle if you are not sure of
their "previous history ." Old used tires may have been damaged
even though the damage cannot be seen that can lead to sudden
tire failure and loss of vehicle control.
• All four wheels must be fitted with radial tires of the same type ,
size (rolling cir cumference ) and the same tread pattern . Driving
&, WARNING (continued )
with different tires reduces vehicle handling and can lead to a loss
of control.
• If the spare tire is not the same as the tires that are mounted
on the vehicle
-for example with winter tires -only use the spare
tire for a short period of time and drive with extra care . Refit the
normal road wheel as soon as safely possible.
• Never drive faster than the maximum speed for which the tires
on your vehicle are rated because tires that are driven faster than
their rated speed can fail suddenly.
• Overloading tires cause heat build -up , sudden tire failure,
including a blowout and sudden deflation and loss of control.
• Temperature grades apply to tires that are properly inflated and
not over or underinflated.
• For techni cal reasons it is not always possible to use wheels
from other vehicles -in some cases not even wheels from the
same vehicle model.
• If you install wheel trim discs on the vehicle wheels , make sure
that the air flow to the brakes is not blocked . Reduced airflow to
the brakes can them to overheat , increasing stopping distances
and causing a collision.
• Run flat tires may only be used on vehicles that were equipped
with them at the factory . The vehicle must have a chassis designed
for run flat tires and a factory-installed tire pressure monitoring
system that indicates a loss of tire pressure. Incorrect use of run
flat tires can lead to vehicle damage or accidents . Check with an
authorized Audi dealer or tire specialist to see if your vehicle can
be equipped with run flat tires . If run flat tires are used , they must
be installed on all four wheels . Mixing tire types is not permitted.
0 Note
• Fo r tec hnica l reaso ns, i t is not gene rally p oss ibl e to use the
whee l rims from other vehicles . T his can hold true for wheels of t he
sa me v ehicl e typ e.
Vehicle care