104n
Antilock Brake System (ABS)The concept ABS keeps the wheels from locking
while braking, thereby enhancing active
driving safety. The reason: 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.
Based on current 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 Ð on all types of road
surfaces (asphalt, concrete, mud,
wet, snow, ice). Braking with ABSThe system becomes operative once
the vehicle exceeds a speed of approx.
6 mph (10 km/h). Whenever the
vehicle's speed drops below approx.
4 mph (6 km/h), the ABS is deactivated.
This means that the wheels can lock in the final phase of a panic stop Ð a factor
of no significance in actual use.
The ABS system works best in situa-
tions requiring maximum pressure on
the pedal ("panic stop"). Do not let up
on the brake pedal even after it starts
pulsating. Since the vehicle maintains
steering responsiveness, you can
nevertheless avoid possible obstacles
with a minimum of steering effort.
The ABS closed-loop control circuit
cycles in fractions of a second. Pulsa-
tion at the brake pedal shows you that
ABS is active, that you are braking
within the ABS' braking range and that
you are thus pushing the limit of the
system. In addition, a pulsation Ð a
result of the control function cycles Ð
indicates to the driver that the vehicle
speed should be reduced to adapt to
road surface conditions 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 for a locked-wheel condition.
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 hitting
the brakes when there is inadequate
distance between vehicles, when the
vehicle is driven at excessive speeds
through curves, or during aquaplaning,
remain the driver's responsibility. 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.< Antilock Brake System (ABS)/
Cornering Brake Control (CBC) CBC is an advanced engineering
design of the ABS. When braking while
cornering at high speed or braking
during high lateral acceleration, or
when braking during a lane change,
vehicle stability is improved and
steering response is enhanced.
114n
Wheel and tire combinations The right choice Use only wheels and tires approved by
BMW for the corresponding vehicle
model, as otherwise the tires may make
contact with the body as the result of
tolerances despite the same nominal
size being used,
resulting in serious accidents. If non-
approved wheels and tires are used,
BMW cannot evaluate their suitability,
and therefore cannot be held liable for
driving safety.<
For wheel and tire specifications
approved by BMW, refer to page 116.
The correct wheel-tire combina-
tion affects different systems that
otherwise will not function properly,
e.g. ABS, DSC.
For this reason, use only tires of the
same brand and tread pattern on the
vehicle and, for example, restore the
approved wheel-tire combination
following a flat tire as soon as
possible.<
Codes on tires and wheels The code on tires has the following
meaning.
Codes on radial tires:
The speed rating indicates the
approved maximum speed for the tire.
Summer tires:
S = up to112 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) e.g.
Nominal width
in mm
Aspect
ratio in X
Radial tire 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 on light-alloy wheels:
Protect valve stems and valves from dirt
using screw-on valve stem caps. Dirt in
the valves frequently leads to slow
leaks. Storage Store tires in a cool, dry place,
protecting them against light when-
ever possible. Protect the tires against
contact with oil, grease and fuel. e.g.
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
8x8H 2
J
