2008 MERCEDES-BENZ G55AMG Owner's Manual

288 Operation
Tires and wheels
Tire inflation pressure changes by approxi-
mately 1.5 psi (0.1 bar) per 18°F (10°C) of
air temperature change. Keep this in mind
when checking tire inflation pressure
where the temperature is different from
the outside temperature.
Checking tire inflation pressure
Regularly check your tire inflation pressure
at least once a month.
Check and adjust the tire inflation
pressure when the tires are cold. The tires
can be considered cold if the vehicle has
been parked for at least 3 hours or driven
less than 1 mile (1.6 km).
If you check the tire inflation pressure
when the tires are warm (the vehicle has
been driven for several miles or sitting less
than 3 hours), the reading will be
approximately 4 psi (0.3 bar) higher than
the cold reading. This is normal. Do not let
air out to match the specified cold tire
inflation pressure. Otherwise, the tire will
be underinflated.
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 over-
heated.
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.
Do not overload the tires by exceeding the
specified load limit as indicated on the Tire
and Loading Information placard 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.
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289
Operation
Tires and wheels
Checking tire inflation pressure
manually
Follow the steps below to achieve correct
tire inflation pressure:
Remove the cap from the valve on one
tire.
Firmly press a tire gauge onto the
valve.
Read tire inflation pressure on tire
gauge and check against the recom-
mended tire inflation pressure on the
Tire and Loading Information placard
on the driver’s
door B-pillar
(
page 280). If necessary, add air to
achieve the recommended tire inflation
pressure.
Install the valve cap.
Repeat this procedure for each tire. Checking tire pressure electronically
with the Advanced Tire Pressure
Monitoring System (Advanced TPMS)
Depending on production date, your vehi-
cle is equipped with a combination low tire
pressure/TPMS malfunction telltale
(USA only) or a low tire pressure telltale
(Canada only).
iIf you have overfilled the tire, release tire
inflation pressure by pushing the metal stem of
the valve with e.g. a tip of a pen. Then recheck
the tire inflation pressure with the tire gauge.
iUSA only:
The T
ire Pressure Monitoring System (TPMS) is
equipped with a combination low tire pres-
sure/TPMS malfunction telltale in the instru-
ment cluster (
page 26). Depending on how the
telltale illuminates, it indicates a low tire pres-
sure condition or a malf unction in the TPMS sys-
tem itself:

If the telltale illuminates continuously, one
or more of your tires is significantly under-in-
flated. There is no malfunction in the TPMS.

If the telltale flashes for 60 seconds and
then stays illuminated, the TPMS system it-
self is not operating properly.
iUSA only:
This device complies with Part 15 of the
FCC Rules. Operation is subject to the following
two conditions:
(1) This device may not cause harmful interfer- ence, and
(2) this device must accept any interference received, including interference that may
cause undesired operation.
Any unauthorized modification to this device
could void the user’s authority to operate the
equipment.
iCanada only:
This device complies with RSS-210 of Industry
Canada. Operation is subject to the following
two conditions:
(1) This device may not cause interference, and
(2) this device must accept any interference received, including interference that may
cause undesired operation of the device.
Any unauthorized modification to this device
could void the user’s authority to operate the
equipment.
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290 Operation
Tires and wheels
The 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.
Tire pressure inquiries are made using the
multifunction display.The present inflation
pressures are displayed only after a few
minutes travel time.Switch on the ignition (page 39).
Press buttonj ork until the
current inflation pressures for each tire
appear in the multifunction display.
Example illustration
iPossible differences between the readings
of a tire pressure gauge of an air hose, e.g. gas
station equipment, and the vehicle’s control
system can occur. Usually the readings issued by
the control system are more precise.
iWhen the vehicle has been parked for longer
than 20 minutes, the message
Tire pressure
displayed only after driving for a few
minutes
appears in the multifunction display.
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 lose control over the vehicle.
iWith a spare wheel mounted, the system
may still indicate the tire inflation pressure of the
removed road wheel for some minutes. If this
happens, keep in mind that the indicated value
where the spare wheel is mounted does not
reflect the actual spare tire inflation pressure.
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291
Operation
Tires and wheels
Warning!G
The Advanced TPMS does not indicate a
warning for wrongly selected inflation pres-
sures. Always adjust ti
re inflation pressure
according to the Tire and Loading Informa-
tion placard on the driver’s door B-pillar or,
if available, the supplemental tire inflation
pressure information on the inside of the
fuel filler flap.
The Advanced TPMS is not able to issue a
warning due to a sudden dramatic loss of
pressure (e.g. tire blowout caused by a for-
eign object). In this case bring the vehicle to
a halt by carefully 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
Tire and Loading Information placard or the
tire inflation pressure label (if available). If
your vehicle has tires of a different size than
the size indicated on the Tire and Loading
Information placard or the tire inflation
pressure label (if av ailable), you should
determine the proper tire inflation pressure
for those tires.
As an added safety feature, your vehicle has
been equipped with an Advanced Tire Pres-
sure Monitoring System (Advanced TPMS)
that illuminates a low tire pressure telltale
when one or more of yo ur tires is significant-
ly underinflated. Acco rdingly, when the low
tire pressure telltale illuminates, you should
stop and check your tires as soon as possi-
ble, and inflate them to the proper pressure.
Driving on a significantly underinflated tire
causes the tire to over heat and can lead to
tire failure.
Underinflation also reduces fuel efficiency
and tire tread life, and may affect the vehi-
cle’s handling and stopping ability. Please
note that the Advanced TPMS is not a sub-
stitute for proper tire maintenance, and it is
the driver’s responsibility to maintain cor-
rect tire pressure, even if underinflation has
not reached the level to trigger illumination
of the Advanced TPMS low tire pressure tell-
tale.
USA only: Your vehicle has also been
equipped with a Advanced TPMS malfunc-
tion indicator to indica te when the system is
not operating properly. The Advanced TPMS
malfunction indicator is combined with the
low tire pressure telltale. When the system
detects a malfunction, the telltale will flash
for approximately 1 minute and then remain
continuously illuminate d. This sequence will
continue upon subsequent vehicle start-ups
as long as the malfunction exists.

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292 Operation
Tires and wheels
Tire inflation pressure warnings
If the system detects a significant loss of
tire inflation pressure in one or more than
one tire, a message appears in the multi-
function display.
Example illustration
The respective tire is indicated by a red
rectangle. In addition, a warning signal
sounds.Restarting Advanced TPMS
The TPMS usually recognizes new refer-
ence values automatically, for example
when you have

adjusted the tire inflation pressure

changed wheels or tires

mounted new wheels or tires
USA only: When the malf
unction indicator is
illuminated, the system may not be able to
detect or signal low tire pressure as
intended.
USA only: Advanced TPMS malfunctions
may occur for a variety of reasons, including
the installation of replacement or alternate
tires or wheels on the vehicle that prevent
the Advanced TPMS from functioning prop-
erly. Always check the Advanced TPMS mal-
function telltale after replacing one or more
tires or wheels on your vehicle to ensure
that the replacement or alternate tires and
wheels allow the Advanc ed TPMS to contin-
ue to function properly.
iOperating radio transmission equipment
(e.g. wireless headsets, two-way radios) in or
near the vehicle could cause the Advanced
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 lose control over the vehicle.

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293
Operation
Tires and wheels
If you want to set new reference values
manually:
Using the Tire and Loading Information
placard on the driver’s door B-pillar
(
page 280) or, if available, the
supplemental tire inflation pressure
information on the inside of the fuel
filler flap (
page 264), make sure the
tire inflation pressure of all four tires is
correct.
Press button è orÿ on the mul-
tifunction steering wheel repeatedly
until the standard display menu
appears in the multifunction display.
Press button j ork repeatedly
until you see the current inflation
pressures for each tire appear in the
multifunction display or the following
message appears in the multifunction
display:
Tire pressure
displayed
only after
driving for
a few minutes
Press the reset button (page 130).
The following message will appear in
the multifunction display:
Restart
tire pressure
monitor?
Press the æ button.
The following message will appear in
the multifunction display:
Tire pressure
monitor
restarted
After driving a few minutes the system
verifies that the cu rrent tire inflation
pressures are within the system’s
specified range. Afte rwards the current
tire inflation pressures are accepted as
reference pressures and then moni-
tored.
If you wish to cancel activation:
Press the ç button.
iRestart the TPMS after adjusting the tire in-
flation pressure to the inflation pressure recom-
mended for the vehicle operating condition. Tire
pressure should only be adjusted on cold tires.
Observe the recommended tire inflation pres-
sure on the Tire and Loading Information placard
on the driver’s door B-pillar (
page 280). Some
vehicles may have supplemental tire inflation
pressure information for driving at high speeds
(
page 287) or for vehicle loads less than the
maximum loaded vehicle condition
(
page 287). If such information is provided, it
can be found on the inside of the fuel filler flap
(
page 264).
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294 Operation
Tires and wheels
Potential problems associated with
underinflated and overinflated tires
Underinflated tires
Underinflated tires can:

cause excessive and uneven tire wear

adversely affect fuel economy

lead to tire failure from being
overheated

adversely affect handling
characteristicsOverinflated tires
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
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:
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.
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295
Operation
Tires and wheels
1
Uniform Quality Grading Standards
(
page 302)
2 DOT, Tire Identification Number (TIN)
(
page 299)
3 Maximum tire load (
page 300)
4 Maximum tire inflation pressure
(
page 301)
5 Manufacturer
6 Tire ply material (
page 304)
7 Tire size designation, load and speed
rating (
page 295)
8 Load identification (
page 298)
9 Tire name Tire size designation, load and speed
rating
1 Tire width
2 Aspect ratio in %
3 Radial tire code
4 Rim diameter
5 Tire load rating
6 Tire speed rating General:
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.
iFor illustration purposes only. Actual data
on tires are specific to each vehicle and may vary
from data shown in above illustration.
For more information, see “Rims and tires”
(
page 414).
iFor illustration purposes only. Actual data
on tires are specific to each vehicle and may vary
from data shown in above illustration.
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