106n
Antilock Brake System (ABS)The concept ABS enhances active safety by helping 
to prevent the wheels from locking dur-
ing brake applications. 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.
The system can achieve the shortest 
braking distances possible under most 
conditions (on straight-aways and in 
curves, on asphalt, ice, wet road sur-
faces, 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, snow, ice).
Braking with ABSThe system becomes operative once 
the vehicle exceeds a speed of approx. 
6 mph (10 km/h). Below approx. 3 mph 
(6 km/h), it is once again deactivated. 
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 maxi-
mum brake pressure ("panic stop"). 
Since the vehicle maintains steering re-
sponsiveness, you can avoid possible 
obstacles with a minimum of steering 
effort, despite the full brake application.
The ABS system closed-loop control 
circuit cycles in fractions of a second. 
A pulsation at the brake pedal indicates 
to the driver that ABS is active, that is, 
that the vehicle is within its maximum 
braking 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 conditions when there is 
reduced traction and grip between tires 
and road surface (slippery road sur-
face).
In driving conditions where there is a 
loose upper surface together with a 
subsurface that provides good traction (on gravel or snow, for instance), or with 
snow chains, the braking distance may 
also be longer than when the wheels 
are locked. However, ABS continues to 
provide enhanced vehicle stability and 
steering response under these condi-
tions.
Information for your safetyNot even ABS can suspend the laws 
of physics. ABS cannot prevent the 
consequences of brake applications 
with inadequate clearances for safety 
between vehicles, when exceeding the 
speed limit in curves, or the risks in-
volved when aquaplaning occurs. Re-
sponsibility for these types of situations 
remains in the hands (and at the feet) 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 increased 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.< 
115n
RepairsIndexOverview Controls Car care Technology Data
Wheel and tire combinations The right choice Use only BMW-approved tires, refer to 
page 117. 
Due to the high speeds this vehicle can 
achieve, the use of specific tire brands, 
specifications and dimensions is man-
datory.
Consult any BMW center for details. 
Comply with local/national regulations.
The correct wheel/tire combinaton 
affects different sytems, such as 
ABS, ATC, DSC. The function of these 
systems can be impaired if the correct 
combinaton is not used.
Therefore, only use tires of the same 
brand and tread pattern. Replace a flat 
tire with an approved wheel/tire combi-
nation as soon as possible.<
Codes on the tires and wheels The tire codes will aid you in selecting 
the correct tire. 
Codes on radial tires:
The speed rating indicates the ap-
proved 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 = above 167 mph (270 km/h)
ZR = above 150 mph (240 km/h) Example:
Nominal width 
in mm
Aspect ratio in % 
Radial tire code
Rim diameter in inches
Load rating
(not on ZR tires)
Speed rating
(before R on ZR tires)
225/50 R
1692W
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 valve inserts against dirt using 
screw-on valve stem caps. Dirt in the 
valves frequently leads to slow leaks. 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
7 x 16 H 2
J