2004 BMW 645CI COUPE tire pressure

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Safety belts
Fasten your safety belt before starting any
trip. Airbags complement the safety belt as
an additional safety device, but they do not
represent a substitute.
Fastening
Make sure you hear the latch plate engage
in the belt buckle.
Please fasten safety belt
warning lamp:
Lights up until the driver and front
passenger have fastened their safety belts.
Depending on the model, a signal
* sounds
or a message
* appears on the Control Dis-
play at the same time.
The warning is also issued when the driver
or front passenger removes his or her
safety belt while driving.
The warning can also take place if
objects are placed on the passenger
seat.<
Releasing
1.Hold the belt firmly
2.Press the red button in the belt buckle
3.Guide the belt into its reel.
The shoulder strap's anchorage point will
be in the correct position for adults of every
build if the seat is correctly adjusted, refer
to page 43.
Damage to safety belts
If the safety belts are damaged or
stretched in an accident: have the
entire belt system, including the tensioning
mechanisms, replaced at your BMW cen-
ter. Have the belt anchorage points
inspected for damage at the same time.
Failure to observe this precaution may pre-
vent the safety belts from effectively pro-
viding optimal protection when needed.<
Heated seats
The system regulates the temperatures of
the seat cushion and backrest.
The temperature setting progresses one
step through its control sequence each
time you press the button.
To switch off:
Maintain pressure on the button for several
seconds.

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have dropped below the minimum, possi-
bly owing to a leak in the hydraulic system.
Do not continue driving. Contact your BMW
center.<
Flat Tire Monitor
The concept
The Flat Tire Monitor keeps track of the
inflation pressures in the four tires as you
drive. The system provides an alert when-
ever the inflation pressure drops signifi-
cantly in relation to the pressure in another
tire.
The check of the tire inflation pressure is
based on monitoring the relative speeds
of the wheels. A flat tire is detected and
reported on the basis of a deviation in cer-
tain speed ratios.
Functional requirement
To ensure reliable operation, the system
should have been initialized with the cor-
rect tire inflation pressure.
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:
>When you are driving on snow-covered
or slippery road surfaces
>In the case of performance-oriented
driving: slip on the drive wheels, high
lateral acceleration
>False alarms and undetected loss of
pressure may occur when you are driv-
ing with snow chains fitted
>If the Flat Tire Monitor was not initial-
ized after the last inflation pressure cor-
rection, false alarms indicating a flat tire
that is not present are possible or pres-
sure loss might not be detected.
Initializing system
Perform the initialization immediately
after correcting the inflation pressure,
after changing a tire or changing a wheel or
all wheels. A drive is necessary for this pur-
pose.<
Control Center, for principle details, refer to
page 16:
1.Start the engine, but do not drive off
2.Open the menu
3.Select "Vehicle settings" and press the
controller
4.Select "FTM" and press the controller
5.Select "Set tire pressure" and press the
controller
6.Select "Yes" and press the controller
7.Drive off.
The message "Initializing" is displayed.
It takes a few minutes before the Flat Tire
Monitor can detect and report a flat tire and
"Status: Active" is displayed.
If a flat tire is detected during initialization,
a message appears on the Control Display.
When driving with snow chains, do
not initialize the system.<

Technology for comfort, convenience and safety
80
Report of a flat tire
The warning lamp lights up in red
and a message appears on the
Control Display. 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
braking and steering maneuvers. Do
not exceed a vehicle speed of 50 mph/
80 km/h
Due to the reinforcement on the
side walls of the run-flat tires,
inflation pressure loss can not usually
be recognized from the outside, refer to
Run-flat tires on page 168.<
2.To continue driving, comply with the
instructions for driving with damaged
tires on page 168.
Malfunction
The warning lamp lights up yellow
and a message appears on the
Control Display. The Flat Tire Moni-
tor has a malfunction or has failed. Have
the system checked as soon as possible.
Active steering*
The concept
The active steering is a system that actively
varies the steering angle of the front wheels
in relation to the steering wheel move-
ments.
When you are driving in the low road speed
range, e.g. in a town or when parking, the
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 of the wheels 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
targeted changes to the steering angle pro-
vided by the driver and thus stabilize the
vehicle before the driver intervenes.
Malfunction
The fixed warning lamp lights up.
The active steering is no longer
operational. In the low speed range,
greater steering wheel movement is neces-
sary. Have the system checked.
If the warning lamp lights up during the first
engine starting following a power supply
interruption, the system must be activated
with initialization.
Initializing system
1.Start the engine
2.With the vehicle stationary, turn the
steering wheel from the straight-ahead
position to the left as far as it will go and
then back to the straight-ahead position
3.Switch off the engine.
When you start the engine again, all the
functions of the active steering are avail-
able once again.
Brake Force Display
The two-stage brake lamps light up in two
stages depending on how strongly you
brake.
>Normal braking:
The brake lamps and the third brake
lamp go on
>Heavy braking and braking with ABS:
In addition, the light area of the rear
brake lamps is enlarged, refer to illus-
tration.

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road surface. This phenomenon is referred
to as hydroplaning, and is characterized
by a partial or complete loss of contact
between the tires and the road surface, ulti-
mately 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 Tire tread on page 167.
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 vehicle's engine, the electri-
cal systems and the transmission may be
damaged.<
Braking safely
Your BMW is equipped with ABS as stan-
dard. The best way to achieve optimized
braking response from the ABS is to apply
maximum pressure to the brake pedal in
situations where this is required: panic
stops. Since the vehicle maintains steering
responsiveness, you can nevertheless
avoid possible obstacles with a minimum
of steering effort.
Pulsation at the brake pedal combines with
sounds from the hydraulic circuits to indi-
cate to the driver that ABS is in its active
mode.
Do not drive with your foot resting on
the brake pedal. Even light but con-
sistent pedal pressure can lead to high
temperatures, brake wear and possibly
even brake failure.<
Driving in wet conditions
While driving in wet conditions and in
heavy rain, it is a good idea to apply light
pressure to the brake pedal every 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 sys-
tem, downshift to a gear in which only min-
imal brake applications are needed when
descending long or steep downhill
stretches. Even light but consistent pedal
pressure can lead to high temperatures,
brake wear and possibly even brake fail-
ure.<
You can further enhance the engine's brak-
ing 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
page 59. This strategy helps you avoid
placing excessive loads on the brake sys-
tem.
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.
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 occasion-
ally, 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 ten-
dency 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 pul-
sating effect that even extended applica-
tion will fail to cure.

Wheels and tires
164
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 condi-
tion of the tires and the maintenance of the
specified tire pressure.
Check the tire inflation pressure regu-
larly and correct it if necessary: at
least every two weeks and before begin-
ning 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.<
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 infla-
tion pressure increases.
After correcting the inflation pres-
sure(s), always reinitialize the Flat Tire
Monitor, refer to page 79.<
Inflation pressures for original tires
The tires must be at ambient temperature.
The inflation pressures, provided on a label
affixed to the B-pillar, are visible when the
driver's door is open.
Inflation pressure 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 corre-
sponding tire size.<
Observe tire size
The specified pressures apply to tire sizes
approved by BMW and recommended tire
makes; your BMW center will be glad to
provide 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
245/45 R 18 96 V, H M+S 29/200 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 page 190.
Tire sizePressure specifications in psi/kPa
All pressure specifications in
the table are indicated in psi/
kilopascal with cold tires –
cold = ambient temperature
245/45 R 18 96 V, H M+S 32/220 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 permitted load and weights can be found on page 190.

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Temperature
The temperature grades are A, the highest,
B, and C, representing the tire's resistance
to the generation of heat and its ability to
dissipate heat when tested under con-
trolled conditions on a specified indoor lab-
oratory test wheel.
Sustained high temperature can cause the
material of the tire to degenerate and
reduce tire life, and excessive temperature
can lead to sudden tire failure. The grade C
corresponds to a level of performance
which all passenger car tires must meet
under the Federal Motor Vehicle Safety
Standard No. 109. Grades B and A repre-
sent higher levels of performance on the
laboratory test wheel than the minimum
required by law.
The temperature grade for this tire is
established for a tire that is properly
inflated and not overloaded. Excessive
speed, underinflation, or excessive load-
ing, either separately or in combination,
can cause heat buildup and possible tire
failure.<
RSC – run-flat tires
You will recognize run-flat tires by a circular
symbol containing the letters RSC on the
side of the tire, refer to page 168.
M+S
Winter and all-season tires.
These have better winter properties than
summer tires.
Tire condition
Before driving off, inspect your tires for
tread wear, signs of damage and foreign
objects lodged in the tread, and check the
tread depth.
Minimum tread depth
The tread depth should not drop below
0.12 in/3 mm, although, for example, Euro-
pean legislation only specifies a minimum
tread depth of 0.063 in/1.6 mm. At tread
depths below 0.12 in/3 mm there is an increased risk of high-speed hydroplaning,
even when only small amounts of water are
present on the road surface.
As winter tires display a noticeable loss in
their ability to cope with cold-weather driv-
ing conditions once the tread wears to
below 0.157 in/4 mm, to ensure continued
safety you should always have such tires
replaced.
Wear indicators at the tread-groove base,
refer to arrow, are distributed over the tire's
circumference and are marked on the side
of the tire with TWI – Tread Wear Indicator.
These indicators signal at a tread depth of
0.063 in/1.6 mm that the legal wear limit
has been reached. The tread is then no
longer visible at these points.
Tire damage
Due to low-profile tires, please note
that wheels, tires and suspension
parts are more susceptible to road hazard
and consequential damages.
Unusual vibrations encountered during
normal vehicle operation can indicate tire
failure or some other vehicle defect. This
can, for example, be caused by driving over
curbs. These kinds of problems may also
be signaled by other changes in vehicle
response, such as a strong tendency to pull
to the left or right.
In these cases, immediately reduce speed.
Drive cautiously to the nearest BMW center
or tire dealer or, if necessary, have the
vehicle towed there.
Tire damage, extending to sudden and
complete loss of pressure in extreme
cases, can pose a potentially lethal safety
hazard for the vehicle's occupants and
other road users alike.<

Wheels and tires
168
Run-flat tires
You will recognize run-flat tires by a circular
symbol containing the letters RSC on the
side of the tire.
Run-flat tires consist of self-contained tires
and special rims. The tire reinforcement
ensures that the tire retains some residual
safety in the event of pressure drop and
driving remains possible to a restricted
degree.
Continuing driving with a damaged
tire
Driving on run-flat tires with tire damage
can continue, depending on the vehicle
load and the severity of the tire damage, at
a maximum speed of 50 mph/80 km/h.
You can estimate the possible mileage for
continued driving on the basis of the fol-
lowing general indications:
>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 track sta-
bility in braking, extended braking distance
and altered natural steering characteristics.
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.<
New wheels and tires
You can find out the right wheel-tire combi-
nation from your BMW center. It is another
vital factor in ensuring reliable operation of
various vehicle systems such as ABS and
DSC. Have the wheel and tire assemblies
balanced every time either a wheel or a tire
is replaced.
Only have new wheels and tires
mounted by a specialist. If this work is
performed inexpertly, there is a danger of
damage and associated safety risks.<
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
substantial – of the carcasses can lead to
unusually rapid wear.<
The right wheels and tires
BMW recommends that you use only
wheel and tire combinations that
BMW has tested and approved for your
particular vehicle. Variations in factors such
as manufacturing 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 accidents. If non-
approved wheels and tires are used, BMW
cannot evaluate their suitability, and there-
fore cannot be held liable for driving
safety.<
To maintain good handling and vehicle
response, use only tires of a single tread
configuration 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 pos-
sible.