BMW 3 (E46). Manual — part 120
from the rear wheel drive version and
have also been relocated to provide front
axle clearance.
The front stabilizer bar has been
increased in diameter to accommodate
the additional weight. See
Table a
.
The struts are shorter than the rear
wheel drive version. Reinforcement
plates have been added between the
strut upper mounting and the strut
towers to prevent sheet metal
deformation when traveling on poor road
surfaces. The spring travel of the E46 all
wheel drive is approximately 20 mm ( 3/4
in.) less than the rear wheel drive
version. The shorter front axle spring
travel is due to the limited angle of
deflection of the front axle shafts.
Each front drive axle shaft has a
conventional constant velocity (CV) joint
at the outboard end and a triple roller
bearing CV joint at the inboard end. The
right inner joint shaft is supported by a
bearing pedestal bolted to the oil pan.
The shaft extends through the engine oil
pan into the front differential.
The front axle differential, bolted to the
left side of the engine oil pan, is driven
by a 40 mm (1.57 in.) single piece
driveshaft. Universal joints are located at
both ends of the driveshaft.
The sport suspension option is not
available for all wheel drive models.
Steering
The variable-assist power steering
system consists of an engine-driven
hydraulic pump, a rack-and-pinion type
steering gear, and connecting linkage to
the road wheels. E46 models utilize an
engine-speed dependent variable effort
steering system. At low speeds,
maximum power assist is provided to
ease parking and city driving. At high
speeds, assist is reduced to ensure
stability.
The steering linkage connects the
rack-and-pinion unit through tie rods to
the steering arms. The tie rod ends allow
the wheels to pivot and react to
suspension travel.
On all wheel drive models, the rack and
pinion steering is constructed with a
larger diameter piston than the rear
wheel drive version. This is necessary to
counter the additional drag of the all
wheel drive system and the wider
standard wheels and tires.
The lower steering column in all wheel
drive models connects to the steering
rack via a universal joint, whereas there
is flexible ("guibo") joint on the rear
wheel drive models. The turning radius
of the all wheel drive vehicle is 35.8 feet,
1.4 feet greater than the rear wheel drive
vehicle.
Rear suspension
The rear suspension subframe (final
drive carrier) is the main mounting point
for the differential housing and rear
suspension components. It is bolted to
the vehicle undercarriage using four
large rubber bushings (arrows).
Trailing arms locate the rear wheels and
anchor the springs, shock absorbers and
stabilizer bar. Drive axles with constant-
velocity (CV) joints at both ends transfer
power from the differential to the road
wheels. The differential is mounted to
the subframe through rubber mounts
and bushings to help isolate drivetrain
noise and vibration.
In all wheel drive models, the rear
suspension and the rear differential have
the same layout as the rear wheel drive
version.
The rear suspension travel of the E46 all
wheel drive is approx. 17 mm (0.67 in.)
less than the rear wheel drive version.
The reason for the reduced travel in the
rear is to prevent excessive body roll as
a result of the higher body profile.
The rear stabilizer bar diameter has
been increased to accommodate the
additional vehicle weight. See
Table
a
.
Table a. E46 stabilizer bars
Model
Front
diameter
Rear
diameter
Rear wheel
drive
23.0 mm
(0.906 in.)
18 mm
(0.709 in.)
All wheel
drive
23.5 mm
(0.925 in.)
20 mm
(0.787 in.)
Sport
suspension
(n/a on awd)
24.0 mm
(0.945 in.)
19 mm
(0.748 in.)
Brakes
E46 cars are equipped with power disc
brakes with integral antilock brakes
(ABS). The parking brake is a dual-drum
system integrated with the rear brake
rotors.
Power assist is provided by a vacuum
booster when the engine is running. The
brake pedal pushrod is connected
directly to the master cylinder, so failure
of the vacuum booster does not normally
result in total brake failure.
Each disc brake uses a caliper with a
single hydraulic cylinder. Brake pads in
the left front and right rear contain wear
sensors. When the pads need
replacement, the sensors illuminate a
light on the dashboard.
Tires and wheels
Tire size is critical to the proper operation
of the anti-lock brake system and
traction control system. Several different
styles of wheels in 15, 16, and 17 inch
diameters are available from an
authorized BMW dealer.
On all wheel drive cars, standard wheel
size is 17x 7.0 to ensure there is enough
room for the front axles and brakes. Tire
size is 205/50 R17.
Tire and rim size applications are listed
in
Table b. Rim and tire sizes
.
Note:
Aftermarket wheels should be selected
with care. Improperly fitted wheels can
contact and damage suspension, brake
or body components and may adversely
affect vehicle stability.
Table b. Rim and tire sizes
Model
Standard
Option
Rim size
Tire size
Rim size
Tire size
323i
15 x 6.5
195/65R 15
16 x 7
205/55R 16
323Ci
325i/Ci
328i
16 x 7
205/55R 16
17 x 8
225/45R 17
328Ci
16 x 7
205/55R 16
17 x 7.5/8.5
225/45R 17
245/45R 17
330i/Ci
17 x 7
205/50R 17
17 x 7.5/8.5
225/45R 17
245/45R 17
325xi
330xi
17 x 7
205/50R 17
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