Page 162 of 201

160Vehicle careIncorrect tyre pressures will impair
safety, vehicle handling, comfort and
fuel economy and will increase tyre
wear.
Tyre pressures differ depending on
various options. For the correct tyre
pressure value, follow the procedure
below:
1. Identify the engine identifier code.
Engine data 3 182.
2. Identify the respective tyre.
The tyre pressure tables show all possible tyre combinations 3 190.
For the tyres approved for your
vehicle, refer to the EEC Certificate of
Conformity provided with your vehicle or other national registration
documents.
The driver is responsible for correct
adjustment of tyre pressures.9 Warning
If the pressure is too low, this can
result in considerable tyre warm-
up and internal damage, leading to tread separation and even to tyre
blow-out at high speeds.
9 Warning
For specific tyres the
recommended tyre pressure as
shown in the tyre pressure table may exceed the maximum tyre
pressure as indicated on the tyre.
Never exceed the maximum tyre
pressure as indicated on the tyre.
If the tyre pressure must be reduced
or increased on a vehicle with tyre
pressure monitoring system, switch
off ignition.
Temperature dependency
The tyre pressure depends on the
temperature of the tyre. During
driving, tyre temperature and
pressure increase. Tyre pressure
values provided on the tyre
information label and tyre pressure
chart are valid for cold tyres, which means at 20 °C.
The pressure increases by nearly
10 kPa (0.1 bar) for a 10 °C
temperature increase. This must be
considered when warm tyres are
checked.
Tyre pressure monitoring
system
The tyre pressure monitoring system
uses radio and sensor technology to
check tyre pressure levels.Caution
Tyre pressure monitoring system
warns only about low tyre pressure condition and does not replace
regular tyre maintenance by the
driver.
The tyre pressure monitoring system sensors monitor the air pressure in
the tyres and transmit tyre pressure
readings to a receiver located in the
vehicle.
All wheels must be equipped with
pressure sensors and the tyres must
have the prescribed pressure.
Tyre pressure chart 3 190.
Page 163 of 201

Vehicle care161Note
In countries where the tyre pressure
monitoring system is legally
required, the use of wheels without
pressure sensors will invalidate the
vehicle type approval.
Low tyre pressure condition
A detected low tyre pressure
condition is indicated by illumination
of control indicator w 3 87 together
with a warning chime. In vehicles with Multifunction version of the Driver
Information Centre, a corresponding message is also displayed.
If w illuminates, stop as soon as
possible and inflate the tyres as
recommended 3 190.
After inflating, driving may be
required to update the tyre pressure
values in the system. During this time
w may illuminate.
If w illuminates at lower temperatures
and extinguishes after some driving,
this could be an indicator for
approaching a low tyre pressure
condition. Check tyre pressure of all
four tyres.
If the tyre pressure must be reduced
or increased, switch off ignition.
Only mount wheels with pressure
sensors, otherwise the tyre pressure
value cannot be recognised by the
system and w flashes for several
seconds then illuminates
continuously. In vehicles with
Multifunction version of the Driver Information Centre, a corresponding
message is also displayed.
A spare wheel or temporary spare
wheel is not equipped with pressure
sensors. The tyre pressure
monitoring system is not operationalfor these wheels. For the further three wheels, tyre pressure monitoring
system remains operational.
Spare wheel 3 167, Wheel changing
3 165.
Control indicator w and (depending
on version) a corresponding message
appears at each ignition cycle until
the tyres are inflated to the correct
tyre pressure.
Driver Information Centre 3 90.
Relearn function
After changing wheels, the tyre
pressure monitoring system needs to recalculate. The relearn process
takes up to 20 minutes of driving with
a minimum speed of 20 km/h.
If problems occur during the relearn
process, control indicator w flashes
for several seconds then illuminates
continuously and (depending on
version) a warning message is
displayed in the Driver Information
Centre.
Driver Information Centre 3 90.
Page 164 of 201

162Vehicle careGeneral information
The use of tyre chains or
commercially available liquid tyre
repair kits can impair the function of
the system. Factory-approved tyre
repair kits can be used.
Tyre repair kit 3 163, Tyre chains
3 163.
Operating electronic devices or being
close to facilities using similar wave
frequencies could disrupt the tyre
pressure monitoring system.
Each time the tyres are replaced, tyre pressure monitoring system sensors
must be dismounted and serviced by
a workshop.
Tread depthCheck tread depth at regular
intervals.
Tyres should be replaced for safety
reasons at a tread depth of 2-3 mm
(4 mm for winter tyres).
For safety reasons, it is
recommended that the tread depth of
the tyres on one axle should not vary
by more than 2 mm.
The legally permissible minimum
tread depth (1.6 mm) has been
reached when the tread has worn
down as far as one of the tread wear
indicators (TWI). Their position is
indicated by markings on the
sidewall.
If there is more wear at the front than
the rear, swap round front wheels and
rear wheels periodically. Ensure that
the direction of rotation of the wheels
is the same as before.
Tyres age, even if they are not used.
We recommend tyre replacement
every six years.
Changing tyre and wheel
size
If tyres of a different size than those
fitted at the factory are used, it may be necessary to reprogramme the
speedometer as well as the nominal
tyre pressure and make other vehicle modifications.
After converting to a different tyre
size, have the label with tyre
pressures replaced.9 Warning
Use of unsuitable tyres or wheels
may lead to accidents and will
invalidate the vehicle type
approval.
Wheel covers
Wheel covers and tyres that are
factory approved for the respective
vehicle and comply with all of the
relevant wheel and tyre combination requirements must be used.
If the wheel covers and tyres used are
not factory approved, the tyres must
not have a rim protection ridge.