1997 BMW 540i Tire

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300-1 4
I Susoension. Steerina and Brakes - General
DSC system I
Dynamic Stability Control (DSC)
Dynamic Stability Control (DSC) utilizes many principles and
components of the ASC traction control system. DSC is ac-
tive throughoutthe driving range, unlike ASC which is only ac-
tive during acceleration and braking. DSC helps stabilize the
vehicle in cornering and avoidance maneuvers by adjusting
engine controls such as throttle, ignition, fuel injection and the
application of
brake pressure individually to the wheels.
Inputs
fi- 0
2 4-* .. o
[11-' IJ
411m4
3?-
G
4 The DSC control module uses various inputs to determine
vehicle instability during braking, cornering, or reduced trac-
tion situations. Based upon these inputs the ABSIDSC con-
trol module sends outputs to the engine control module and
the ABSIDSC hydraulic unit to activate torque reduction pro-
tocols and braking intervention.
-
ABSIDSC control module
OUI~YIS
4
The DSC system can be toggled on and off by a switch
mounted on the center console. Turning off the DSC system
does not disable ABS or ASC functions.
+
Measure ride height (A) from center of fender arch to bottom
of wheel rim.
Car in normal loaded position on the ground. See Normal
loaded position.
Engine
control
module
Specified tires and wheels, correct tire pressure, even tire
wear
-'* 9-
.%A
Correct wheel bearing play
T'== ..t, 9 B
-.m
Model with air suspension (EHC): Disconnect electrical har-
ness connector to air supply pump to prevent automatic
height regulation.
When finished, reset ride height using BMW diagnostic
scan tools DIS or
MoDiC.
NOTE-
Airsupply pump is located beneath a cover under the spare
tire in the floor of the cargo compartment.
- If ride height is outside specification listed, install new
springs. Suspension spring removal and installation is cov-
ered in
310 Front Suspension and 330 Rear Suspension.
Normal loaded position
Each front seat 68 kg (150 Ib)
Center of rear seat 68 kg (150 lb)
Trunk 21 kg (46 lb)
Fuel tank full

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/~ront Susaension
Front suspension arms FRONT SUSPENSION ARMS
Scyllnder models (5251,5281,530i)
Control arms and tension struts are attached to the front sub-
Front suspension arms V-8 models (5401)
frame through rubber bushings and to the steering ltnuckles
by ball joints.
NOTE-
Tension struts are sometimes called thrust arms or thrust
rods.
Control arms or tension struts are sometimes called lower
front arms or lower rear arms.
Inspect ball joints for wear and looseness. lnspect bushings
for wear or fluid
lealts. The ball joint can only be replaced as
part of an entire suspension arm assembly. Some suspen-
sion arm
bushinas are available as re~lacement Darts. Al-
ways replace in pairs
NOTE-
Steering wheel vibration during braking (usually at road
speeds of
50 to 60 m.p.h.) are often causedby faulty suspen-
sion arm bushings, not out-of-true brake rotors.
Some special tools may be required to remove suspension
arms and to replace bushings. Read procedures through be-
fore beginning the job.
Control arm, removing and installing
(6-cylinder models)
- Raise car and remove wheel
Male sure
that the car is firmly supported on jack stands de-
signed for the purpose. Place jack stands underneath struc-
tural chassis points. Do not place jack stands under
suspension
parfs.
Cars equipped with vertical headlight adjustment system:
Disconnect control arm from level sensor.
Remove control arm fasteners (arrows). Lightly tap inner
control arm mounting bolt out of subframe.

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I Steering and Wheel Alignment
- Installation is reverse of removal, noting the following:
Replace shear bolts at steering column mounting bracket.
Tighten until bolt heads shear off.
Make sure
interlock cable snaps into place.
When installing column top trim panel, replace expansion
nut for trim retaining screw.
NOTE-
The steering angle sensor must be coded using a BMW scan
tool if it has been replaced.
A steering angle offset check
must then be carried out using the same
BMW scan tool.
CAUTION-
Check steering system for freedom of movement through en-
tire steering column
adiustment range.
Tightening torques Steering shaft coupler
to steering shaft 25 Nm (18 ft-lb)
(replace bolt)
Steering column to body
22 Nm (16 ft-lb)
Steering column adjustment motors,
removing and installing
Remove lower dash panel mounting fasteners (A) and (B).
- Lower panel and disconnect wiring harness from back side.
- Remove steering column lower trim panel. See Steering col-
umn trim, removing and replacing.
- Disconnect electrical harness from motor.
Remove motor mounting fasteners (arrows)
Slide motor to side and forward to remove.
Installation is reverse of removal.

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Steering and Wheel Alignment
- Tighten nut while counterholding adjusting bolt,
- Tighten nut only after car has been lowered to ground and
suspension has settled.
Preparing for alignment
- The following conditions are necessary prior to wheel align-
ment:
Correct wheels and tires are installed, in good condition,
and are at the correct inflation pressures.
All steering and suspension parts and bushings are un-
damaged and show no signs of abnormal wear. Wheel
bearings are in good condition.
Ride height is in accordance with specifications. See
300
Suspension, Steering and Brakes-General.
Car is in normal loaded position. See below.
* Cars with air suspension: Remove air suspension power
fuse.
Normal loaded position
Each front seat
68 Kg (I50 lb)
Center of rear seat
Trunlc
Fuel tank
68 Kg (150 lb)
21 Kg (46 lb)
Full
Alignment specifications tables
In the alignment specification tables that follow, reference is
made to the various types of suspension used in
E39 cars.
The type of suspension can be identified by loolting at the la-
bel on the front strut tube.
Identifying symbol
None
Solid circle
Solid triangle
M5
Circle
Triangle Version
Standard suspension
Sports
suspension
Sports suspension
M sport package
Standard suspension
Sports suspension Model
Sedan
6-cylinder sedan
V-8 sedan
V-8 sedan
Touring (Sport Wagon)
Touring (Sport Wagon)

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--
C. -- -- - -- Rear ~us~ensionl
Depending on year and model applications, the Sport Wagon
rear suspension may be equipped with:
Conventional shock absorbers and coil springs
Electronic height control (EHC) system which incorporates
air springs
NOTE-
. Suspension and EHC troubleshooting is covered in 300
Suspension, Steering and Brakes-General.
EHC system repairs, other than air spring replacement,
are covered in Electronic height control
(EHC) compo-
nent replacement.
Replace shock absorbers and springs in pairs only.
Rear shock absorber, removing and
installing
- Raise car and remove rear wheels,
WARNING-
Male sure that the car is firmly supported on jack stands de-
signed for the purpose. Place jack stands underneath struc-
tural chassis points. Do not place
jack stands under
suspension parts.
CAUTION-
If working on a vehicle with compressedairshock absorbers,
disable air supply pump by disconnecting electrical plug be-
fore performing any repairs. Pump is located beneath a cover
under the spare tire in the floor of the cargo compartment.
- Support swing arm from below
CAUTIOG
The shock absorber prevents the drive axle and wlieel bear-
ing carrier from dropping too far. Supporting the wheel bear-
ing carrier before disconnecting the shock absorber
mounting fasteners prevents damage to the
brake hose,
parking
brake cable and drive axle CVjoints.
- Working in cargo compartment, remove carpet. Remove tri-
angular upper shock mount covers located beside spare tire
well.
- If applicable: Detach air supply line from shock absorber.
Plug ports and lines to keep out dirt.

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Rear Suspension
Air spring, removing and installing
CAUTION-
If vehicle is driven with airspring depressurized, the airspring
will be permanently damaged and must be replaced.
An air spring is made from a flexible rubber material which
forms an airtight cavity. It is pressurized by an air supply
pump activated by an electronic control unit to provide a
vari- . . able spring rate depending on vehicle load
CAUTIOIG
Disable air supply pump by disconnecting electrical plug
before performing any repairs. Pump is located beneath a
cover under the spare tire in the floor of
the cargo compart-
ment.
When removing and installing air connections, extreme
cleanliness must be followed. Small dirt particles can
cause leakage in the system.
Remove luggage compartment floor mat.
- Working above air spring, loosen quick coupling screw con-
nection to allow
air pressure to escape.
- Once pressure has been reduced, retighten screw.
Tightening torque Quick coupling screw
to air pump 2 Nm (18 in-lb)
- Remove quick coupler. Plug openings to keep dirt out,
- Remove air spring mounting clips.
- Raise car and remove rear wheels.
Make sure the car is firmly supported on jack stands de-
signed for the purpose. Place jack stands underneath struc-
tural chassis points. Do not place
jaclc stands under
suspension parts.
- Working underneath rear suspension, lift wheel bearing car-
rier to relieve rear spring tension. Then unbolt air spring
mounting bolt from seat on wheel bearing carrier. Remove air
spring.
NOTE-
Left and right air springs are different. The left air spring is
marked with a red identification
marl. The right air spring is
marked with a blue identification mark.

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Rear Suspension Swing arm, removing and installing
(Sport Wagon models)
- Raise rear end of car and remove wheel.
WARNING -
Make sure the car is firmly supported on jack stands de-
signed for the purpose. Place jack stands underneath struc-
tural chassis points. Do not place jack stands under
suspension parts.
CAUJION-
Model with air springs: Disable air supply pump by discon-
necting electricalplug
beforeperforminganyrepairs. Pump is
located beneath a cover under the spare tire in the floor of the
cargo compartment.
< Model with air springs: Loosen compressed air pipes (ar-
rows) at air distribution assembly to release system pres-
sure.
NOJE-
Vehicle will stand quite low
- If applicable: Detach air supply line from shock absorber.
Plug ports and lines to
lkeep out dirt.
- Model with rear coil springs: Remove cargo compartment
floor carpet.
4 Working at top of coil spring, press center cap down or pry
upward to remove. If pushed down, remove from inside coil
spring from under car.
4 Working from underneath, position BMW special tool
33
2 301 between 2nd and 3rd spring coil from bottom.
Make sure tool recess faces upward.
Working in cargo compartment, guide BMW special tool
33
2 304 from above and thread into special tool 33 2 301.

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330-1 9
Rear suspension1
Swing arm ball joint, replacing
- Raise rear end of car and remove wheel.
Make sure the car is firmly supported on jack stands de-
signed for the purpose. Place jack stands underneath struc-
tural chassis points. Do not place jack stands under
suspension
parts.
- Sport Wagon model: Support wheel bearing carrier from be-
low.
CA
UTION-
The shock absorberprevents the drive axle and wheel bear-
ing carrier from dropping too far. Supporting the wheel bear-
ing carrier before disconnecting the
shoclc absorber
mounting fastenerprevents damage to the brake hose, park-
ing
brake cable and drive axle CVjoints.
- Model with air shock absorbers: Detach air supply line from
shoclc absorber. Plug ports and lines to keep out dirt.
- Sport Wagon model: Remove shock absorber lower mount-
ing bolt.
4 Remove stabilizer bar link mounting nut (arrow). Press link
out of swing arm.
Model with air springs: Disable air supply pump by discon-
necting electrical plug before performing any repairs. Pump is
located beneath a cover under
the spare tire in the floor of the
carao
comoartment.
4 Model with air springs: Loosen compressed air pipes (ar-
rows) at air distribution assembly to release system pres.
sure.
WARNING-
Vehicle will lower when the air pipes are opened.
- Models with rear coil springs: Remove cargo compartment
floor carpet.