106n
Antilock Brake System (ABS)The concept ABS helps prevent the wheels from
locking while braking, thereby
enhancing active driving safety. This is
because locked wheels are dangerous.
When the front wheels slide, the driver
loses steering control over the vehicle.
Traction loss at the rear wheels can
cause the rear end to break into an
uncontrolled skid.
Under any given road conditions, ABS
can brake the vehicle within the
shortest possible distance and with the
greatest possible driving stability (on
straight-aways and curves, asphalt, ice,
wet road surfaces, etc.).
ABS is designed to meet two essential
requirements during every brake appli-
cation:
>To help provide vehicle stability
>To help maintain steering control and
maneuverability – on all types of road
surfaces (asphalt, concrete, mud, wet
road surfaces, snow, ice).
Braking with ABSThe system is operative once the
vehicle exceeds a speed of approx.
6 mph (10 km/h). The ABS is deacti-
vated whenever the vehicle's speed
drops back below approx. 4 mph
(6 km/h). This means that the wheels
can lock in the final phase of a panic
stop – a factor of no significance in
actual use.
If you are in a situation that requires full
braking, you will exploit the full benefits
of the ABS system if you apply
maximum pedal pressure ("panic stop").
Do not let up on the brake pedal even
after it starts pulsating. Since the
vehicle maintains steering response,
you retain the ability to avoid obstacles
using careful steering inputs.
The ABS system's closed-loop control
circuit cycles in fractions of a second.
Pulsation at the brake pedal shows you
that ABS is active and that you are thus
approaching the limits of the brake
system's effective response range. In
addition, a pulsation – a result of the
control function cycles – indicates to
the driver that vehicle speed should be
reduced to adapt to road surface condi-
tions when there is reduced traction and grip between tires and road surface
(slippery road surface).
On road surfaces with a loose surface
layer over a firm base, e.g. on gravel or
snow, as well as when driving with
snow chains on, braking distances may
be longer than with the wheels locked.
However, ABS continues to provide
enhanced vehicle stability and steering
response under these conditions.
Information for your safetyNot even ABS can suspend the laws of
physics. The consequences of brake
applications with inadequate clear-
ances for safety between vehicles,
excessive speed or if aquaplaning
occurs are always the responsibility of
the driver. You should never allow the
added safety of ABS to lull you into a
false sense of security, or mislead you
into taking risks that could affect your
own safety and that of others.
Do not make any modifications to
the ABS system.
Service procedures on ABS are to be
performed by authorized technicians
only.<
118n
Wheel and tire combinations The right choice
Only use wheels and tires that
have been approved by BMW for
the corresponding vehicle model, as
otherwise body contact and serious
accidents can result despite the use of
the same nominal size, e.g. due to
tolerances. BMW cannot evaluate non-
approved wheels and tires to determine
if they are suited for use, and therefore
cannot ensure the operating safety of
the vehicle if they are installed.<
For wheel and tire sizes approved by
BMW, refer to page 120.
Failure to use the specified wheel
and tire combinatons can have an
adverse effect on the performance of
various systems such as ABS and DSC.
For this reason, use only tires made by
the same manufacturer and that have
the same tread configuration on the
vehicle. And after a flat tire, for
instance, restore the approved wheel
and tire combination as soon as
possible.<
Codes on the tires and wheels The marking on the tire has the
following meaning.
The codes on radial tires:
The speed rating indicates the
approved maximum speed for the tire.
Summer tires:
S = up to 112 mph (180 km/h)
T = up to 118 mph (190 km/h)
H = up to 130 mph (210 km/h)
V = up to 150 mph (240 km/h)
W = up to 167 mph (270 km/h)
Y = up to 187 mph (300 km/h)
ZR = over 150 mph (240 km/h) Example:
Nominal width
in mm
Aspect
ratio in %
Radial tire ID code
Rim diameter in inches
Load rating
(not on ZR tires)
Speed rating
(before R on ZR tires)
225/45 R
1892W
Winter tires:
Q M+S = up to 100 mph (160 km/h)
T M+S = up to 118 mph (190 km/h)
H M+S = up to 130 mph (210 km/h)
Codes stamped on light-alloy wheels:
Protect tire valve from dirt by using
screw-on valve stem caps. Dirt in the
valves frequently leads to slow leaks. Storage Always store tires in a cool, dry place.
Store them away from light whenever
possible. Protect the tires against
contact with oil, grease and fuel. Example:
Rim width
in inches
Code letter for
flange type
Symbol for full-drop
center rim
Rim diameter in inches
Hump on the 2 rim shoulders
8 x 18 H 2
J
