2005 BMW 645CI CONVERTIBLE tire pressure

Technology for comfort, convenience and safety
84
Flat Tire Monitor
The concept
The Flat Tire Monitor keeps track of the infla-
tion pressures in the four tires as you drive. The
system provides an alert whenever the inflation
pressure drops significantly in relation to the
pressure in another tire.
When a loss of pressure occurs, the rolling
radius changes and with it, the rotational speed
of the wheels. This change is detected and sig-
naled as a flat tire.
Functional requirement
To ensure the reliable signaling of a flat tire, the
system must be initialized at the correct tire
inflation pressure.
The initialization must be repeated after
every correction of the tire inflation pres-
sure and after every tire or wheel change.<
System limits
The Flat Tire Monitor cannot indicate
sudden severe tire damage caused by
outside factors and does not detect a natural,
even pressure drop in all four tires.<
In the following situations, the system could be
delayed or malfunction:
>System has not been initialized
>Driving on snow-covered or slippery roads
>Sporty driving style: slip in the drive wheels,
high lateral acceleration
>When driving with snow chains
*
Initializing system
The initialization is completed during driv-
ing, which can be interrupted at any time.
When driving continues, the initialization is also
automatically continued.
Do not initialize the system when driving with
snow chains
*.<
Control Center, for principle details, refer to
page16.1.Press the button
This opens the start menu.
2.Press the controller to open the menu.
3.Select "Vehicle settings" and press the
controller.
4.Select "FTM" and press the controller.
5.Start engine, but do not start driving.
6.Select "Set tire pressure" and press the
controller.
7.Select "Yes" and press the controller.
8.Release.
The message "Initializing" is displayed.
The initialization is completed during driv-
ing. Then "Status: Active" appears on the
Control Display again.

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Report of a flat tire
The warning lamp lights up in red. A
message appears on the Control Dis-
play. In addition, an acoustic signal
sounds. There is a flat tire or extensive inflation
pressure loss.
1.Cautiously reduce the vehicle speed to
below 50 mph/80 km/h. Avoid sudden brak-
ing and steering maneuvers. Do not exceed
a vehicle speed of 50 mph/80 km/h.
If the vehicle is not, as provided at the
factory, equipped with run-flat tires,
refer to page172, stop driving. Continued
driving after a flat tire can result in serious
accidents.<
2.Check the air pressure in all four tires at the
next opportunity.
If the tire inflation pressure in all four
tires is correct, the Flat Tire Monitor
may not have been initialized. The system
must then be initialized.<
3.In case of a complete loss of the tire inflation
pressure or obvious tire damage, you can
estimate the possible driving distance for
continued driving base on the following ref-
erence values:
>With low load:
1 to 2 persons without luggage:
approx. 155 miles/250 km.
>With medium load:
2 persons, luggage compartment full, or
4 persons without luggage:
approx. 94 miles/150 km.
>With full load:
4 persons, luggage compartment full:
approx. 30 miles/50 km.
Drive reservedly and do not exceed
a speed of 50 mph/80 km/h. In the
event of pressure loss, vehicle handling
changes. This includes reduced tracking
stability in braking, extended braking dis-
tance and altered natural steering charac-
teristics.
If unusual vibrations occur while the vehicle
is being driven, this can indicate final failure
of the damaged tire. Reduce speed and stop as soon as possible. Do not continue
driving. Contact your BMW center.<
Malfunction
The warning lamp lights up in yellow. A
message appears on the Control Dis-
play. The Flat Tire Monitor has a mal-
function or has failed. Have the system checked
as soon as possible.
Active steering*
The concept
The active steering is a system that actively var-
ies the steering angle of the front wheels in rela-
tion to the steering wheel movements.
A t l o w s p e e d , e . g . i n a t o w n o r w h e n p a r k i n g , t h e
steering angle of the wheels is reinforced, i.e.
the steering becomes very direct.
In the higher speed range, on the other hand,
the steering angle is reduced more and more.
This improves the handling capability of your
BMW over the entire speed range.
In critical situations, the system can make tar-
geted corrections to the steering angle pro-
vided by the driver and thus stabilize the vehicle
before the driver intervenes. This stability-pro-
moting intervention is deactivated when DSC is
switched off, refer to page82.
Malfunction
The warning lamp lights up. The active
steering is no longer operational. At low
speed, larger steering wheel move-
ments are required, while the vehicle reacts
more sensitively to steering wheel movements
in the higher road-speed range. Have the sys-
tem checked.
If the warning lamp lights up during the first
engine starting following a power supply inter-
ruption, the system must be activated by being
initialized.

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Mobile communication devices in
vehicle
BMW advises against using mobile com-
munication devices, e.g. portable phones,
inside the vehicle without a direct connection to
an external antenna. Otherwise, the vehicle
electronics and mobile communication device
can influence one another. In addition, there is
no assurance that the radiation emitted during
transmission will be conveyed out of the vehicle
interior.<
Hydroplaning
When driving on wet or slushy roads,
reduce road speed. If you do not, a wedge
of water can form between tires and road sur-
face. This phenomenon is referred to as hydro-
planing, and is characterized by a partial or
complete loss of contact between the tires and
the road surface, ultimately undermining your
ability to steer and brake the vehicle.<
The risk of hydroplaning increases as the tread
depth of the tires decreases, also refer to Mini-
mum tire tread on page171.
Driving through water
Do not drive through water on the road if it
is deeper than 1 ft/30 cm, and then only at
walking speed at the most. Otherwise, the vehi-
cle's engine, the electrical systems and the
transmission may be damaged.<
Using handbrake on inclines.
On inclines, do not hold the vehicle with
the clutch; use the handbrake. Otherwise
greater clutch wear will result.<
SMG Sequential manual transmission
Start off quickly on slopes. Do not hold
the vehicle on a hill by applying the throt-
tle, but engage the handbrake instead. Other-
wise overheating can occur in the transmission
region.<
Braking safely
Your BMW is equipped with ABS as standard. In
situations that require it, it is best to brake with
full force. Since the vehicle maintains steering
responsiveness, you can still avoid possible
obstacles with a minimum of steering effort.
Pulsation at the brake pedal combines with
sounds from the hydraulic circuits to indicate to
the driver that ABS is in its active mode.
Do not drive with your foot resting on the
brake pedal. Even light but consistent
pedal pressure can lead to high temperatures,
brake wear and possibly even brake failure.<
Driving in wet conditions
When driving on wet roads or in heavy rain,
briefly brake with light pedal pressure at inter-
vals of a few miles. Monitor traffic conditions to
ensure that this maneuver does not endanger
other road users. The heat generated in this
process helps dry the pads and rotors to ensure
that full braking efficiency will then be available
when you need it.
Hills
To prevent overheating and thus reduced
efficiency of the brake system, downshift
to a gear in which only minimal brake applica-
tions are needed when descending long or
steep downhill stretches. Even light but consis-
tent pedal pressure can lead to high tempera-
tures, brake wear and possibly even brake fail-
ure.<
You can further enhance the engine's braking
effect by selecting a lower gear in the automatic
transmission's manual mode, downshifting as
far as first gear on extremely steep stretches,
refer to page58. This strategy helps you avoid
placing excessive loads on the brake system.
Never drive with the clutch pressed
or allow the vehicle to coast with the
transmission in Neutral – or with the engine
switched off – there is no engine braking when
the transmission is in Neutral, and no power
assist for brakes and steering when the engine
is not running.

Things to remember when driving
110 Never allow floor mats, carpets or any other
objects to protrude into the area around the
accelerator and brake pedals and obstruct their
movement.<
Corrosion on brake rotors
When the vehicle is driven only occasionally,
during extended periods when the vehicle is not
used at all, and in operating conditions where
brake applications are less frequent, there is an
increased tendency for corrosion to form on
rotors, while contaminants accumulate on the
brake pads. This occurs because the minimum
pressure which must be exerted by the pads
during brake applications to clean the rotors is
not reached.
Should corrosion form on the brake rotors, the
brakes will tend to respond with a pulsating
effect that even extended application will fail to
cure.
When the vehicle is parked
Condensation forms in the automatic air condi-
tioner system during operation, and then exits
under the vehicle. Traces of condensed water
under the vehicle are therefore normal.
Before driving into a car wash
To prevent the exterior mirrors from being
damaged due to the width of the vehicle,
always fold them in by hand before entering an
automatic car wash.<
Cargo loading
To avoid loading the tires beyond their
approved carrying capacity, never over-
load the vehicle. Overloading can lead to over-
heating and increases the rate at which damage
develops inside the tires. The ultimate result
can assume the form of a sudden blow-out.<
Determining loading limit
1.Locate the following statement on your
vehicle's placard
*:
The combined weight of occupants
and cargo should never exceed
XXX lbs. or YYY kg, as otherwise the vehicle
may be damaged and unstable driving con-
ditions may result.<
2.Determine the combined weight of the
driver and passengers that will be riding in
your vehicle.
3.Subtract the combined weight of the driver
and passengers from XXX lbs. or YYY kg.
4.The resulting figure equals the available
amount of cargo and luggage load capacity.
For example, if the XXX amount equals
800 lbs. and there will be four 150-lbs. pas-
sengers in your vehicle, the amount of avail-
able cargo and luggage load capacity is
200 lbs.:
800 lbs. minus 600 lbs. = 200 lbs.
5.Determine the combined weight of luggage
and cargo being loaded on the vehicle. That
weight may not safely exceed the available
cargo and luggage load capacity calculated
in step 4.
6.If your vehicle will be towing a trailer, part of
the load from your trailer will be transferred
to your vehicle. Consult the manual for
transporting a trailer to determine how this
may reduce the available cargo and luggage
load capacity of your vehicle.

Wheels and tires
168
Wheels and tires
Tire inflation pressure
Information for your safety
It is not merely the tire's service life, but also
driving comfort and – to a great extent – driving
safety that depend on the condition of the tires
and the maintenance of the specified tire pres-
sure.
Checking tire inflation pressure
Only check tire inflation pressure when the tires
are cold. This means after a maximum of
1.25 miles/2 km driving or when the vehicle has
been parked for at least 2 hours. When tires are
warm, the tire inflation pressure increases.
Check the tire inflation pressure regularly
and correct it if necessary: at least every
two weeks and before beginning a longer trip. If
you fail to observe this precaution, you may be
driving on tires with incorrect tire pressures, a
condition that can not only compromise your
vehicle's stability, but also lead to tire damage
and the risk of an accident.<
After correcting the inflation pressure(s),
always reinitialize the Flat Tire Monitor,
refer to page84.<
Pressure specifications for factory-
installed tires
The tire inflation pressures with the ambient
temperature are visible on the door pillar with
the driver's door open.
Pressure specifications for other tire
sizes
The tables below provide all the correct inflation
pressures for the specified tire sizes at ambient
temperature.
For correct identification of the right tire
inflation pressure for your tires, observe
the specifications for the corresponding tire
size.<
Tire size
The specified pressures apply to tire sizes
approved by BMW and recommended tire
m a k e s ; y o u r B M W c en t e r w i ll b e g l a d t o p ro v id e
information.

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645Ci Coupe
645Ci Convertible
Tire sizePressure specifications in psi/kPa
All pressure specifications in
the table are indicated in psi/
kilopascal with cold tires –
cold = ambient temperature
245/50 R 17 99 H M+S
245/45 R 18 96 V M+S
245/45 R 18 96 V M+S all season29/200 32/220 33/230 39/270
Front: 245/45 R 18 96 W
Rear: 275/40 R 18 99 W29/200
––
32/22033/230
––
39/270
Front: 245/40 R 19 94 W
Rear: 275/35 R 19 96 W29/200
––
32/22033/230
––
39/270
Front: 245/35 R 20 91 Y
Rear: 275/30 R 20 93 Y29/200
––
32/22033/230
––
39/270
More details on the permitted load and weights can be found on page192.
Tire sizePressure specifications in psi/kPa
All pressure specifications in
the table are indicated in psi/
kilopascal with cold tires –
cold = ambient temperature
245/50 R 17 99 H M+S
245/45 R 18 96 V M+S
245/45 R 18 96 V M+S all season32/220 38/260 39/270 46/320
Front: 245/45 R 18 96 W
Rear: 275/40 R 18 99 W32/220
––
38/26039/270
––
46/320
Front: 245/40 R 19 94 W
Rear: 275/35 R 19 96 W32/220
––
38/26039/270
––
46/320
Front: 245/35 R 20 91 Y
Rear: 275/30 R 20 93 Y32/220
––
38/26039/270
––
46/320
More details on the permissible load and weights can be found on page192.

Wheels and tires
172
Run-flat tires
You will recognize run-flat tires by the circular
symbol containing the letters RSC on the side-
wall.
Run-flat tires consist of self-contained tires and
special rims. The sidewall reinforcement
ensures that the tire retains some residual
safety in the event of pressure drop and driving
remains possible to a restricted degree.
New wheels and tires
Only have new wheels and tires mounted
by a BMW center or a specialized tire
dealer which works with personnel trained in
accordance with BMW specifications. If this
work is performed inexpertly, there is a danger
of damage and associated safety risks. Make
sure that the new wheels are balanced.<
Retreaded tires
BMW does not recommend the use of
retread tires, as otherwise driving safety
may be reduced. Possible variations in the
design and the age – which could be substan-
tial – of the carcasses can lead to more rapid
wear.<
The right wheels and tires
If you switch from summer to winter tires, or
vice versa, use run-flat tires, as in the event of a
flat tire there is no spare tire available. Your
BMW center will be glad to advise you.
For safety reasons, BMW recommends
that you do not have damaged run-flat
tires repaired; they should be replaced. wheel and tire combinations that BMW
has tested and approved for your particular
vehicle. Variations in factors such as manufac-
turing tolerances mean that even wheels and
tires with identical official size ratings could
actually have different dimensions than the
approved units – these differences could lead to
body contact, and with it the risk of severe acci-
dents. If non-approved wheels and tires are
used, BMW cannot evaluate their suitability,
and therefore cannot be held liable for driving
safety.<
You can find out the right wheel-tire combina-
tion from your BMW center.
The right wheel-and-tire combination is
another vital factor in ensuring reliable opera-
tion of various vehicle systems such as ABS
and DSC.
To maintain good handling and vehicle
response, use only tires of a single tread config-
uration from a single manufacturer. After a flat
tire, always remember to have the specified
wheel and tire combination remounted on the
vehicle as soon as possible.
Recommended tire brands
BMW tests certain tire brands for each tire size,
classifies them as road-safe and approves
them. Consult your BMW center for more infor-
mation. Observe any country-specific regula-
tions, e.g. on making a corresponding entry in
the vehicle documents.
The factory-mounted tires have been specially
selected to provide optimized performance
when installed on your vehicle; if properly cared
for, they will provide a combination of safety and
excellent ride comfort.
Special characteristics of winter tires
BMW recommends winter tires for use in cold
winter driving conditions. Although all-season
M+S tires provide better winter traction than
summer tires, they generally fail to provide the
same levels of cold-weather performance as
winter tires.

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Run-flat tires
If you switch from summer to winter tires, or
vice versa, use run-flat tires, refer to page172,
as in the event of a flat tire there is no spare tire
available. Your BMW center will be glad to
advise you.
Watch speed
Observe the permissible maximum speed
for the respective winter tires, as other-
wise tire damage and occur and cause acci-
dents.<
Storage
Always store wheels and tires in a cool, dry
place with as little exposure to light as possible.
Always protect tires against all contact with oil,
grease and fuels. Do not exceed the maximum
tire inflation pressure indicated on the side wall
of the tire.
Snow chains*
BMW only tests certain fine-link snow chains,
classifies them as road-safe and approves
them. Consult your BMW center for more infor-
mation. BMW recommends using these
approved snow chains. These snow chains are
approved exclusively for use in pairs on the rear
wheels with the tire size:
>245/50 R 17 Y
>245/45 R 18 Y
Observe the chain manufacturer's instructions
when mounting snow chains. Do not exceed a
vehicle speed of 30 mph/50 km/h with the
chains mounted.
Do not initialize the Flat Tire Monitor after
mounting snow chains.
When you are driving with snow chains, it can
be beneficial to switch off DTC briefly, refer to
page82.<