Page 337 of 521

336 OperationTires and wheelsThe TPMS only functions on wheels that
are equipped with the proper electronic
sensors. It monitors the tire inflation pres-
sure, as selected by the driver, in all four
tires. A warning is issued to alert you to a
decrease in pressure in one or more of the
tires.Warning!
G
The TPMS does not indicate a warning for
wrongly selected inflation pressures. Always
adjust tire inflation pressure according to
the placard on the driver’s door B-pillar or, if
available, the supplemental tire pressure in-
formation on the inside of the fuel filler flap.
The TPMS is not able to issue a warning due
to a sudden dramatic loss of pressure (e.g.
tire blowout caused by a foreign object). In
this case bring the vehicle to a halt by care-
fully applying the brakes and avoiding
abrupt steering maneuvers.
Warning!
G
Each tire, including the spare (if provided),
should be checked monthly when cold and
inflated to the inflation pressure recom-
mended by the vehicle manufacturer on the
vehicle placard or the tire inflation pressure
label. (If your vehicle has tires of a different
size than the size indicated on the vehicle
placard or the tire inflation pressure label,
you should determine the proper tire infla-
tion pressure for those tires).
As an added safety feature, your vehicle has
been equipped with a tire pressure monitor-
ing system (TPMS) that illuminates a low tire
pressure telltale when one or more of your
tires is significantly under-inflated. Accord-
ingly, when the low tire pressure telltale illu-
minates, you should stop and check your
tires as soon as possible, and inflate them to
the proper pressure. Driving on a significant-
ly under-inflated tire causes the tire to over-
heat and can lead to tire failure.
Under-inflation also reduces fuel efficiency
and tire tread life, and may affect the vehi-
cle’s handling and stopping ability. Please
note that the TPMS is not a substitute for
proper tire maintenance, and it is the driv-
er’s responsibility to maintain correct tire
pressure, even if under-inflation has not
reached the level to trigger illumination of
the TPMS low tire pressure telltale.
Your vehicle has also been equipped with a
TPMS malfunction indicator to indicate
when the system is not operating properly.
The TPMS malfunction indicator is com-
bined with the low tire pressure telltale.
When the system detects a malfunction, the
telltale will flash for approximately
one minute and then remain continuously
illuminated. This sequence will continue
upon subsequent vehicle start-ups as long
as the malfunction exists. When the mal-
function indicator is illuminated, the system
may not be able to detect or signal low tire
pressure as intended.
Page 338 of 521

337 Operation
Tires and wheels
Reactivating the TPMS*
The TPMS must be reactivated when you
have adjusted the tire inflation pressure to
a new level (e.g. because of different load
or driving conditions). The TPMS is then
recalibrated to the current tire inflation
pressures.
Using the tire placard on the driver’s
door B-pillar (
page 328) or, if avail-
able, the supplemental tire pressure
information on the inside of the fuel fill-
er flap (
page 312), make sure the tire
inflation pressure of all four tires is cor-
rect.
TPMS malfunctions may occur for a variety
of reasons, including the installation of in-
compatible replacement or alternate tires or
wheels on the vehicle that prevent the TPMS
from functioning properly. Always check the
TPMS malfunction telltale after replacing
one or more tires or wheels on your vehicle
to ensure that the replacement or alternate
tires and wheels allow the TPMS to continue
to function properly.
iIf a condition causing the TPMS to mal-
function develops, it may take up
to 10 minutes for the system to signal
a malfunction using the TPMS telltale
flashing and illumination sequence.
The telltale extinguishes after a few
minutes driving if the malfunction has
been corrected.iOperating radio transmission equip-
ment (e.g. wireless headsets, two-way
radios) in or near the vehicle could
cause the TPMS to malfunction.
Warning!
G
It is the driver’s responsibility to calibrate
the TPMS on the recommended cold infla-
tion pressure. Underinflated tires affect the
ability to steer or brake the vehicle. You
might loose control over the vehicle.
Page 339 of 521

338 OperationTires and wheels
Press buttonè orÿ on the mul-
tifunction steering wheel repeatedly
until the standard display menu ap-
pears in the multifunction display
(page 155).
Press thej or kbutton repeat-
edly until you see the flowing message:Tire pressure
monitor active
Reactivation possible:
R-button
Press the reset button.
The following message will appear in
the multifunction display:Check current
tire pressure?
Press the æbutton.
The following message will appear in
the multifunction display:Tire pres. monitor
reactivatedAfter driving a few minutes the system
verifies that the current tire inflation
pressures are within the system’s
specified range. Afterwards the current
tire inflation pressures are accepted as
reference pressures and then moni-
tored.
If you wish to cancel activation:
Press the çbutton.
iReactivate the TPMS after adjusting
the tire inflation pressure to the infla-
tion pressure recommended for the
vehicle operating condition. Tire pres-
sure should only be adjusted on cold
tires. Observe the recommended tire
inflation pressure on the placard on the
driver’s door B-pillar (
page 328).
Some vehicles may have supplemental
tire pressure information for driving at
high speeds (
page 334) or for vehicle
loads less than the maximum loaded
vehicle condition. If such information is
provided, it can be found on the inside
of the fuel filler flap.
Page 340 of 521

339 Operation
Tires and wheels
Potential problems associated with
underinflated and overinflated tires
Underinflated tire inflation pressure
Underinflated tires can:
cause excessive and uneven tire wear
adversely affect fuel economy
lead to tire failure from being
overheated
adversely affect handling
characteristicsOverinflated tire inflation pressure
Overinflated tires can:
adversely affect handling
characteristics
cause uneven tire wear
be more prone to damage from road
hazards
adversely affect ride comfort
increase stopping distance
Warning!
G
Follow recommended tire inflation
pressures.
Do not underinflate tires. Underinflated tires
wear excessively and/or unevenly,
adversely affect handling and fuel economy,
and are more likely to fail from being
overheated.
Warning!
G
Follow recommended tire inflation
pressures.
Do not overinflate tires. Overinflated tires
can adversely affect handling and ride
comfort, wear unevenly, increase stopping
distance, and result in sudden deflation
(blowout) because they are more likely to
become punctured or damaged by road
debris, potholes etc.
Page 341 of 521

340 OperationTires and wheelsMOExtended system*
The MOExtended system allows you to
continue driving your vehicle even if there
is a total loss of pressure in one or more
tires.
You may only use the MOExtended system
with the Tire Pressure Monitoring System*
(TPMS*) (
page 335).
For information on driving in case of pres-
sure loss in one or more tires (emergency
mode), see the “Practical hints” section
(
page 451).
Tire labeling
Besides tire name (sales designation) and
manufacturer name, a number of markings
can be found on a tire.
Following are some explanations for the
markings on your vehicle’s tires:1Uniform Quality Grading Standards
(
page 348)
2DOT, Tire Identification Number (TIN)
(page 345)
3Maximum tire load (
page 346)
4Maximum tire inflation pressure
(
page 347)
5Manufacturer
6Tire ply material (
page 350)
7Tire size designation, load and speed
rating (
page 341)
8Load identification (
page 344)
9Tire name
iFor illustration purposes only. Actual
data on tires are specific to each vehi-
cle and may vary from data shown in
above illustration.
For more information, see “Rims and
tires” (
page 472).
Page 342 of 521

341 Operation
Tires and wheels
Tire size designation, load and speed
rating
1Tire width
2Aspect ratio in %
3Radial tire code
4Rim diameter
5Tire load rating
6Tire speed ratingGeneral:
Depending on the design standards used,
the tire size molded into the sidewall may
have no letter or a letter preceding the tire
size designation.
No letter preceding the size designation
(as illustrated above): Passenger car tire
based on European design standards.
Letter “P” preceding the size designation:
Passenger car tire based on U.S. design
standards.
Letter “LT” preceding the size designation:
Light Truck tire based on U.S. design
standards.
Letter “T” preceding the size designation:
Temporary spare tires which are high
pressure compact spares designed for
temporary emergency use only. Tire width
The tire width1 (
page 341) indicates
the nominal tire width in mm.
Aspect ratio
The aspect ratio2 (page 341) is the
dimensional relationship between tire
section height and section width and is
expressed in percentage. The aspect ratio
is arrived at by dividing section height by
section width.
Tire code
The tire code3 (
page 341) indicates
the tire construction type. The “R” stands
for radial tire type. Letter “D” means
diagonal or bias ply construction; letter “B”
means belted-bias ply construction.
At the tire manufacturer’s option, any tire
with a speed capability above 149 mph
(240 km/h) can include a “ZR” in the size
designation (for example: 245/40 ZR 18).
For additional information, see “Tire speed
rating” (
page 343).
iFor illustration purposes only. Actual
data on tires are specific to each vehi-
cle and may vary from data shown in
above illustration.
Page 343 of 521

342 OperationTires and wheelsRim diameter
The rim diameter4 (
page 341) is the
diameter of the bead seat, not the
diameter of the rim edge. Rim diameter is
indicated in inches (in).
Tire load rating
The tire load rating5 (page 341) is a
numerical code associated with the
maximum load a tire can support.
For example, a load rating of 91 corre-
sponds to a maximum load of 1 356 lbs
(615 kg) the tire is designed to support.
See also “Maximum tire load”
(
page 346) where the maximum load as-
sociated with the load index is indicated in
kilograms and lbs.For additional information on tire load
rating, see “Load identification”
(
page 344).
Warning!
G
The tire load rating must always be at least
half of the GAWR (
page 351) of your vehi-
cle. Otherwise, tire failure may be the result
which may cause an accident and/or seri-
ous personal injury to you or others.
Always replace rims and tires with the same
designation, manufacturer and type as
shown on the original part.
Warning!
G
Do not overload the tires by exceeding the
specified load limit or vehicle capacity
weight as indicated on the placard located
on the driver’s door B-pillar. Overloading the
tires can overheat them, possibly causing a
blowout. Overloading the tires can also
result in handling or steering problems, or
brake failure.
iTire load rating5 (
page 341) and
Tire speed rating6 (page 341) are
also referred to as “service descrip-
tion”.
Page 344 of 521

343 Operation
Tires and wheels
Tire speed rating
The tire speed rating6 (
page 341)
indicates the approved maximum speed
for the tire.Summer tires
At the tire manufacturer’s option, any
tire with a speed capability above
149 mph (240 km/h) can include a
“ZR” in the size designation (for exam-
ple: 245/40 ZR18). To determine the
maximum speed capability of the tire,
the service description for the tire must
be referred to. The service description is comprised of the tire load rating5
(
page 341) and the tire speed
rating6 (
page 341).
If your tire includes “ZR” in the size
designation and no service
description5 and6 (
page 341) is
given, the tire manufacturer must be
consulted for the maximum speed ca-
pability.
If a service description5 and6
(
page 341) is given, the speed capa-
bility is limited by the speed symbol in
the service description.
Example: 245/40 ZR18 97Y.
In this example, “97Y” is the service
description. The letter “Y” designates
the speed rating and the speed capabil-
ity of the tire is limited to 186 mph
(300 km/h).
Warning!
G
Even when permitted by law, never operate
a vehicle at speeds greater than the
maximum speed rating of the tires.
Exceeding the maximum speed for which
tires are rated can lead to sudden tire
failure, causing loss of vehicle control and
possibly resulting in an accident and/or
personal injury and possible death, for you
and for others. iTire load rating5 (
page 341) and
Tire speed rating6 (page 341) are
also referred to as “service descrip-
tion”.
Index
Speed rating
Q
up to 100 mph (160 km/h)
R
up to 106 mph (170 km/h)
S
up to 112 mph (180 km/h)
T
up to 118 mph (190 km/h)
H
up to 130 mph (210 km/h)
V
up to 149 mph (240 km/h)
W
up to 168 mph (270 km/h)
Y
up to 186 mph (300 km/h)
(Y)
above 186 mph (300 km/h)
ZR
above 149 mph (240 km/h)