inflation pressure MERCEDES-BENZ R-Class 2012 W251 Owner's Manual

It is important for your safety and that of your
passenger to have deployed air bags replaced
and to have any malfunctioning air bags
repaired. This will help to make sure the air
bags continue to perform their protective
function for the vehicle occupants in the
event of a crash.
Front air bags
The front air bags increase protection for the
driver's and front-passenger's head and
chest.
Driver's air bag : deploys in front of the
steering wheel; front-passenger front air
bag ; deploys in front of and above the glove
box.
They are deployed:
R in the event of certain frontal impacts
R if the system determines that air bag
deployment can offer additional protection
to that provided by the seat belt
R if the seat belt is fastened
R independently of other air bags in the
vehicle
If the vehicle overturns, the front air bags are
generally not deployed unless the system
detects high vehicle deceleration in a
longitudinal direction.
Your vehicle has adaptive, two-stage front air
bags. In the event of a collision, the air bag
control unit evaluates the vehicle
deceleration. In the first deployment stage,
the front air bag is filled with enough
propellant gas to reduce the risk of injuries.
The front air bag is fully deployed if a second
deployment threshold is exceeded within a
few milliseconds.
The deployment of the front-passenger front
air bag is also influenced by the weight
category of the front passenger, which is
determined by the Occupant Classification
System (OCS) ( Y page 44).
The lighter the passenger side occupant, the
higher the vehicle deceleration rate required
(predicted at the start of the impact) for
second stage inflation of the front-passenger
front air bag. In the second stage, the front
air bags are inflated with the maximum
amount of propellant gas available.
The front air bags are not deployed in
situations where a low impact severity is
predicted. You will then be protected by the
fastened seat belt.
The front-passenger front air bag will only
deploy if:
R the system, based on the OCS weight
sensor readings, detects that the front-
passenger seat is occupied.
R
R the air bag control unit predicts a high
impact severity.
Side impact air bagsGWARNING
The pressure sensors for side impact air bag
control are located in the doors. Do not
modify any components of the doors or door
trim panels including, for example, the
addition of door speakers.
Improper repair work on the doors or the
modification or addition of components to the
doors create a risk of rendering the side
impact air bags inoperative or causing
unintended air bag deployment. Work on the
doors must therefore only be performed by
qualified technicians. Contact an authorized
Mercedes-Benz Center.
42Occupant safetySafety

Display messagesPossible causes/consequences and M SolutionsDISTRONIC
InoperativeDISTRONIC is defective or the display has failed.XVisit a qualified specialist workshop.DISTRONIC
Currently
Unavailable See
Operator's ManualDISTRONIC is deactivated and is temporarily inoperative if:
R the DISTRONIC cover in the radiator grill is dirty.
R its function is impaired due to heavy rain, snow or fog.
R the radar sensor system is temporarily inoperative, e.g. due to
electromagnetic radiation emitted by nearby TV or radio
stations or other sources of electromagnetic radiation.
R the radar sensor system has not detected any vehicles or
stationary objects, e.g. traffic signs, for a long time.
R the system is outside the operating temperature range.
DISTRONIC becomes available again and the display message
disappears if:
R the dirt (e.g. slush) drops away while the vehicle is in motion.
R the system detects that the sensors are fully available again.
R the system is within the operating temperature range.
If the display message continues to be displayed:XClean the DISTRONIC cover in the radiator grill ( Y page 291).XRestart the engine.GWARNING
DISTRONIC cannot take weather conditions into account. Switch off DISTRONIC or do not turn
it on if the sensor is dirty or visibility is diminished as a result of snow, rain or fog. The distance
control may be impaired even before the system is able to detect a dirty sensor. The DISTRONIC
Currently Unavailable See Operator's Manual message will be displayed in the
multifunction display and DISTRONIC will be turned off.
Tires
GWARNING
Do not drive with a flat tire. A flat tire affects the ability to steer or brake the vehicle. You may
lose control of the vehicle. Continued driving with a flat tire will cause excessive heat build-up
and possibly a fire.
GWARNING
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.
Display messages231On-board computer and displaysZ

Driving systemsProblemPossible causes/consequences and M Solutions·
The red distance
warning lamp lights up
while the vehicle is in
motion. A warning tone
also sounds.GRisk of accident
The warning is issued if you approach a stationary vehicle or a
vehicle driving ahead of you at too high a speed.
XBe prepared to brake immediately.XPay careful attention to the traffic situation. You may have to
brake or take evasive action.
More information about DISTRONIC (Y page 173) and the distance
warning signal ( Y page 68).
Tires
ProblemPossible causes/consequences and M Solutionsh
USA only:
The yellow tire pressure
monitor warning lamp
(pressure loss/
malfunction) is lit.GRisk of accident
The tire pressure monitor has detected a loss of pressure in at
least one of the tires.
XStop the vehicle without making any sudden steering or braking
maneuvers. Pay attention to the traffic conditions as you do so.XObserve the additional display messages in the multifunction
display.XCheck the tire pressure. If necessary, correct the tire pressure
( Y page 331).XIf necessary, change a wheel ( Y page 346).h
USA only:
The yellow tire pressure
monitor warning lamp
(pressure loss/
malfunction) flashes for
60 seconds and then
remains lit.The tire pressure monitor is defective.XObserve the additional display messages in the multifunction
display.XVisit a qualified specialist workshop.GWARNING
Each tire, including the spare (if provided), should be checked every other week when cold and
inflated to the inflation pressure recommended by the vehicle manufacturer on the Tire and
Loading Information placard on the driver's door B-pillar or, if available, the tire inflation pressure
label on the inside of the fuel filler flap. If your vehicle has tires of a different size than the size
Warning and indicator lamps in the instrument cluster245On-board computer and displaysZ

indicated on the Tire and Loading Information placard or, if available, the tire inflation pressure
label, you should determine the proper tire inflation pressure for those tires.
As an added safety feature, your vehicle has been equipped with a tire pressure monitoring
system (TPMS) that illuminates a low tire pressure warning lamp when one or more of your tires
are significantly underinflated. Accordingly, when the low tire pressure warning lamp illuminates,
you should stop and check your tires as soon as possible, and inflate them to the proper pressure.
Driving on a significantly underinflated tire causes the tire to overheat and can lead to tire failure.
Underinflation also reduces fuel efficiency and tire tread life, and may affect the vehicle's handling
and stopping ability. Please note that the TPMS is not a substitute for proper tire maintenance,
and it is the driver's responsibility to maintain correct tire pressure, even if underinflation has
not reached the level to trigger illumination of the TPMS low tire pressure warning lamp.
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 combined with the low tire
pressure warning lamp. When the system detects a malfunction, the warning lamp 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 malfunction
indicator is lit, the system may not be able to detect or signal low tire pressure as intended.
TPMS malfunctions may occur for a variety of reasons, including the installation of incompatible
replacement or alternate tires or wheels on the vehicle that prevent the TPMS from functioning
properly. Always check the TPMS malfunction warning lamp 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.246Warning and indicator lamps in the instrument clusterOn-board computer and displays

Flat tire
Preparing the vehicle
Your vehicle may be equipped with a
collapsible spare wheel or MOExtended tires
(tires with run-flat properties) ( Y page 309).
i Vehicle preparation is not necessary on
vehicles with MOExtended tires.
i Vehicles equipped with MOExtended tires
are not equipped with a TIREFIT kit at the
factory. It is therefore recommended that
you additionally equip your vehicle with a
TIREFIT kit if you mount tires that do not
feature run-flat properties, e.g. winter tires.
A TIREFIT kit can be obtained from an
authorized Mercedes-Benz Center.
XVehicles with the AIRMATIC package: make
sure that highway level is selected
( Y page 180).XStop the vehicle as far away as possible
from traffic on solid, non-slippery and level
ground.XSwitch on the hazard warning lamps.XFirmly depress the parking brake.XBring the front wheels into the straight-
ahead position.XMove the DIRECT SELECT lever to P.XSwitch off the engine.XVehicles without KEYLESS-GO: remove
the SmartKey from the ignition lock.XVehicles with KEYLESS-GO: open the
driver's door.
The on-board electronics have status 0,
which is the same as the SmartKey having
been removed.XVehicles with KEYLESS-GO: remove the
Start/Stop button from the ignition lock
( Y page 145).XAll occupants must get out of the vehicle.
Make sure that they are not endangered as
they do so.XMake sure that no one is near the danger
area while a wheel is being changed.Anyone who is not directly assisting in the
wheel change should, for example, stand
behind the barrier.XGet out of the vehicle. Pay attention to
traffic conditions when doing so.XClose the driver's door.
i Only operate the tire inflation compressor
using the socket in the footwell of the
second row of seats ( Y page 268), even if
the ignition is turned off.
An emergency cut-off ensures that the on-
board electrical system voltage does not
drop too low. If the on-board electrical
system voltage is too low, power to the
sockets is automatically cut off. This
ensures that there is sufficient power to
start the engine.
TIREFIT kit
Using the TIREFIT kit
You can use the TIREFIT kit to seal small
punctures, particularly those in the tire tread.
You can use TIREFIT at outside temperatures
down to -4 ‡ (-20 †).
GWARNING
TIREFIT is a limited repair device. TIREFIT
cannot be used for cuts or punctures larger
than approximately 0.16 in (4 mm) and tire
damage caused by driving with extremely low
tire inflation pressure, or on a flat tire, or a
damaged wheel.
Do not drive the vehicle under such
circumstances.
Contact the nearest authorized Mercedes-
Benz Center for assistance or call Roadside
Assistance.
XDo not remove any foreign objects which
have penetrated the tire, e.g. screws or
nails.XRemove the tire sealant bottle, the
accompanying "max. 80 km/h" sticker and
the tire inflation compressor from theFlat tire299Breakdown assistanceZ

stowage well underneath the trunk floor
( Y page 296).XAffix part : of the sticker within the
driver's field of vision.XAffix part ; of the sticker near the valve
on the wheel with the defective tire.GWARNING
Take care not to allow the contents of TIREFIT
to come in contact with hair, eyes or clothing.
TIREFIT is harmful if inhaled, swallowed or
absorbed through the skin - causes skin, eye
and respiratory irritation.
Any contact with eyes or skin should be
flushed immediately with plenty of water.
If clothing comes in contact with TIREFIT,
change clothing as soon as possible.
In case of allergic reaction or rash, consult a
physician immediately.
GWARNING
Keep TIREFIT away from children. If
swallowed, rinse mouth immediately with
plenty of water and drink plenty of water.
Do not induce vomiting.
Consult a doctor immediately.
Keep away from open flame or heat source.
i If TIREFIT leaks out, allow it to dry. It can
then be removed like a layer of film.
If you get TIREFIT on your clothing, have it
cleaned as soon as possible with
perchloroethylene.
Your vehicle is provided with one of two
different tire inflation compressors:
R Version 1: the hose with the pressure
gauge and the cable are behind a flap.
R Version 2: the pressure gauge is in the tire
inflation compressor.
TIREFIT kit version 1XOpen flap ;.XPull connector A with the cable and hose
B out of the housing.XScrew hose B onto flange C of tire
sealant bottle :.XInsert tire sealant bottle : head
downwards into recess = of the tire
inflation compressor.XRemove the cap from valve E on the faulty
tire.300Flat tireBreakdown assistance

XMake sure pressure release screw F on
pressure gauge G is fully closed.XScrew filler hose D onto valve E.XInsert connector A into the socket in the
footwell of the second row of seats
( Y page 268).
!
None of the other sockets or cigarette
lighters are designed for operating the tire
inflation compressor.
XTurn the SmartKey to position
1 (Y page 145) in the ignition lock.XPress on/off switch ? on the tire inflation
compressor to I.
The tire inflation compressor is switched
on. The tire is inflated.
i First, TIREFIT is pumped into the tire. The
pressure can briefly rise to approximately
500 kPa (5 bar/73 psi).
Do not switch off the tire inflation
compressor during this phase.
XAllow the tire inflation compressor to run
for five minutes. The tire should then have
attained a pressure of at least 180 kPa
(1.8 bar/26 psi).
! Do not operate the tire inflation
compressor for longer than eight minutes
at a time without a break. It may otherwise
overheat.
The tire inflation compressor can be
operated again once it has cooled down.
If a pressure of 180 kPa (1.8 bar/26 psi) has
been achieved after five minutes, see
( Y page 302).
If a pressure of 180 kPa (1.8 bar/26 psi) has
not been achieved after five minutes, see
( Y page 302).
TIREFIT kit version 2XPull connector ? with the cable and hose
A out of the housing.XScrew hose A onto flange B of tire
sealant bottle :.XInsert tire sealant bottle : head
downwards into recess ; of the tire
inflation compressor.XRemove the cap from valve C on the faulty
tire.XScrew filler hose D onto valve C.XInsert connector ? into the socket in the
footwell of the second row of seats
( Y page 268).Flat tire301Breakdown assistanceZ

! None of the other sockets or cigarette
lighters are designed for operating the tire
inflation compressor.XTurn the SmartKey to position
1 (Y page 145) in the ignition lock.XPress on/off switch = on the tire inflation
compressor to I.
The tire inflation compressor is switched
on. The tire is inflated.
i First, TIREFIT is pumped into the tire. The
pressure can briefly rise to approximately
500 kPa (5 bar/73 psi).
Do not switch off the tire inflation
compressor during this phase.
XAllow the tire inflation compressor to run
for five minutes. The tire should then have
attained a pressure of at least 180 kPa
(1.8 bar/26 psi).
! Do not operate the tire inflation
compressor for longer than eight minutes
at a time without a break. It may otherwise
overheat.
The tire inflation compressor can be
operated again once it has cooled down.
If a pressure of 180 kPa (1.8 bar/26 psi) has
been achieved after five minutes, see
( Y page 302).
If a pressure of 180 kPa (1.8 bar/26 psi) has
not been achieved after five minutes, see
( Y page 302).
Tire pressure of at least 180 kPa
(1.8 bar/26 psi) is not reached
If, after five minutes, a pressure of 180 kPa
(1.8 bar/26 psi) has not been achieved:
XPress the on/off switch on the tire inflation
compressor to 0.
The tire inflation compressor is switched
off.XUnscrew the filler hose from the valve of
the faulty tire.XVery slowly drive forwards or reverse
approximately 30 ft (10 m).XPump up the tire again.GWARNING
If after five minutes a pressure of 180 kPa
(1.8 bar/26 psi) cannot be achieved, the tire
is too badly damaged to be repaired reliably
using TIREFIT.
In this case TIREFIT cannot seal the tire
properly.
Do not drive any further.
Contact the nearest authorized Mercedes-
Benz Center for assistance or call Roadside
Assistance.
Tire pressure of 180 kPa (1.8 bar/
26 psi) is reached
XPress the on/off switch on the tire inflation
compressor to 0.
The tire inflation compressor is switched
off.XUnscrew the filler hose from the valve of
the faulty tire.
! After use, excess TIREFIT may run out of
the filler hose. This could cause stains.
Therefore, place the filler hose in the plastic
bag which contained the TIREFIT kit.
XStow the tire sealant bottle and the tire
inflation compressor.XPull away immediately .GWARNING
Do not exceed a vehicle speed of 50 mph
(80 km/h ). A TIREFIT repair is not designed to
operate at higher speeds.
The sticker must be attached on the
instrument cluster where it will be easily seen
by the driver.
Vehicle handling characteristics of a TIREFIT
repaired tire may change. Adapt your driving
accordingly.
302Flat tireBreakdown assistance

XStop after driving for approximately ten
minutes and check the tire pressure with
the tire inflation compressor.GWARNING
If tire inflation pressure has fallen below
130 kPa (1.3 bar/26 psi) do not continue to
drive the vehicle.
Park your vehicle safely away from the
roadway and contact the nearest authorized
Mercedes-Benz Center or Roadside
Assistance.
Have the damaged tire replaced.
XCorrect the tire pressure if it is at least
130 kPa (1.3 bar/20 psi) (for the required
values, see the Tire and Loading
Information placard on the driver's side
B-pillar or the tire pressure table inside the
fuel filler flap).XTo increase the tire pressure: switch on
the tire inflation compressor.
TIREFIT kit version 1
XTo reduce the tire pressure (version 1):
open pressure release screw F on
pressure gauge G.
TIREFIT kit version 2
EPressure release buttonFPressure gaugeXTo reduce the tire pressure (version 2):
press pressure release button E on the
filler hose.XStow the tire sealant bottle and the tire
inflation compressor.XDrive to the nearest workshop and have the
tire changed there.XHave the tire sealant bottle replaced as
soon as possible at a qualified specialist
workshop, e.g. at an authorized Mercedes-
Benz Center.HEnvironmental note
Have the used tire sealant bottle disposed of
professionally, e.g. at an authorized
Mercedes-Benz Center.
XHave the tire sealant bottle replaced every
four years at a qualified specialist
workshop, e.g. an authorized Mercedes-
Benz Center.
Changing a wheel and mounting the
spare wheel
Preparing the vehicle
GWARNING
The wheel and tire size of the emergency
spare wheel/spare wheel may differ to that of
the damaged wheel. When using an
emergency spare wheel/spare wheel the
Flat tire303Breakdown assistanceZ

Mounting a new wheelGWARNING
Always replace wheel bolts that are damaged
or rusted.
Never apply oil or grease to wheel bolts.
Damaged wheel hub threads should be
repaired immediately. Do not continue to
drive under these circumstances! Contact an
authorized Mercedes-Benz Center or call
Roadside Assistance.
Incorrect wheel bolts or improperly tightened
wheel bolts can cause the wheel to come off.
This could cause an accident. Make sure to
use the correct wheel bolts.
GWARNING
Only use genuine Mercedes-Benz wheel bolts.
Other wheel bolts may come loose.
Do not tighten the wheel bolts when the
vehicle is raised. Otherwise, the vehicle could
fall off the jack.
:Wheel bolts for 18", 19" and 20" wheels2Wheel bolts for the collapsible spare
wheel
! Always use wheel bolts ; to mount the
collapsible spare wheel. Using other wheel
bolts to mount the collapsible spare wheel
could damage the brake system.
GWARNING
Make sure to use the original length wheel
bolts when remounting the original wheel
after it has been repaired.
XClean the wheel and wheel hub contact
surfaces.
! To prevent damage to the paintwork, hold
the wheel securely against the wheel hub
while screwing in the first wheel bolt.
XSlide the emergency spare wheel onto the
alignment bolt and push it on.XTighten the wheel bolts until they are
finger-tight.XUnscrew the alignment bolt.XTighten the last wheel bolt until it is finger-
tight.XInflate the collapsible spare wheel
( Y page 307).
Inflating the collapsible spare wheel
GWARNING
Inflate the collapsible spare wheel only after
the wheel is properly attached.
Inflate the collapsible spare wheel using the
tire inflation compressor before lowering the
vehicle.
Your vehicle is equipped with one of two tire
inflation compressors:
R Version 1: tire inflation compressor with a
pressure gauge on the air hose
R Version 2: tire inflation compressor with
an integrated pressure gauge
The following description applies to both
versions. Differences in the way they are used
will be explained in detail.
Flat tire307Breakdown assistanceZ