BMW 3 Series suspension technology:The milestones (2): Thanks to sporty, agile and safe handling, the fifth generation of BMW's bestseller sets a further benchmark in terms of driving fun.

Munich. More driving fun in the medium class car segment: It was under
this premise that, in 1975, BMW presented an entirely new concept. With
the BMW 3 Series brand-typical virtues such as dynamics and agility
became factors of success in this segment for the very first time. The
sporty saloon's unique handling characteristics convinced right from
the word go. The unmistakable character of the BMW 3 Series was the
result of a consistently implemented basic concept: high-performance
engines were complemented by power transfer to the rear wheels, even
load distribution and an advanced chassis construction. As early
as1975, the technically sophisticated wheel suspension, remarkably
precise, torque steer-free steering and powerful brakes guaranteed the
driver of a BMW 3 Series car exceptionally sporty and safe vehicle
handling in any situation. A standard still applicable to this very
day. Even if every single component of the suspension technology has
been subject to a remarkable development process over the past 33
years, the basic concept of driving pleasure does indeed remain in
existence to this very day. Thanks to the most modern suspension system
in its segment, the BMW 3 Series today still sets the benchmark in
sportiness and agile handling. 1975: Premiere of the BMW 3 Series -
performance and suspension at luxury class level. The new series was
launched in 1975, comprising the BMW 316, the BMW 318, the BMW 320 and
the BMW 320i and four engine variants. With its 98 bhp four-cylinder
engine even the BMW 318 almost entered the domain of triple-digit
performance values then predominantly reserved only to luxury class
vehicles. However, in terms of suspension technology, all versions of
the BMW 3 Series already surpassed normal standards typical of their
respective segment. They were also a match for pure sports cars. The
sports suspension featured by the first model generation had wheels
individually suspended on transverse arms with spring struts at the
front and likewise, at the rear, independent wheel suspension with
semi-trailing arms and spring struts. This combination facilitated the
harmonisation of an above-average driving dynamics potential with a
high degree of comfort. The transverse arms on the front axle were
guided by stabilisers according to the McPherson principle, the new
front axle construction offering ideal preconditions for high steering
precision. Also, with the BMW 3 Series an entirely new design feature
made its debut at BMW - the flexibly mounted rack-and-pinion steering.
The steering column now comprised the following components: steering
shaft, cardan joint and flexible discs. Better performance, enhanced
technology: disc brakes all round and optional servo steering for the
six-cylinder versions. The BMW 3 Series of the first generation came
with 13-inch steel rims as standard. Alloys of the same size were
available as an option. Thanks to disc brakes on the front wheels and
drum brakes at the rear, excellent deceleration values were achieved
from the word go. However, with the introduction to the BMW 3 Series of
the exceptionally powerful six-cylinder power units, it became
necessary to employ brakes that were even more effective. Consequently,
the BMW 323i, the series' top-of-the-range model launched in 1977 and
delivering 105 kW/143 bhp, was also equipped with disc brakes on the
rear wheels. Moreover, as in the case of the BMW 320/6, the steering
could be optionally fitted with hydraulic power steering technology.
1982: The second generation - even more agile, even safer. 1982 saw the
arrival of the second generation of the BMW 3 Series, a worthy
successor to the trendsetter and bestseller. The new model reflected
advancement and variety in every aspect - new design, optimised
aerodynamics, increased space and comfort, higher power output,
additional body and engine variants. For example, during its lifespan a
four-door version, the first BMW 3 Series Touring, the Convertible and
the BMW M3 sports car were introduced. Furthermore, diesel engines and
four-wheel drive were added to the BMW 3 Series portfolio. This
strategy was most successful. With more than 2.3 million units sold,
its predecessor's sales figures were topped by a million vehicles. In
terms of agility, driving safety and handling precision the second
generation of the BMW 3 Series also outshone all competitors in its
segment. Engineers had modified the front axle of the new BMW 3 Series
in order to increase active safety even further, without affecting the
typical handling characteristics. At the front, the new 3 Series
featured a single-joint spring strut suspension with sickle-shaped
transverse control arms and a reduced rolling radius to minimise the
negative forces that affect steering. The rear axle now incorporated
semi-trailing arms with separate dampers and springs. The newly
designed barrel springs with progressive spring characteristics
provided enhanced comfort, particularly on slightly uneven road
surfaces, and thanks to their compact design they also facilitated an
increase in boot capacity. The linkage of the rear semi-trailing arms
now had a sweep of only 15 degrees instead of 20. Furthermore, the
track, now widened by 35 millimetres, the low weight and reduced
aerodynamic resistance had a positive effect on the driving
characteristics of the new BMW 3 Series. At the time of its launch,
there was a choice of the two four-cylinder models BMW 316 (66 kW/90
bhp) and BMW 318i (77 kW/105 bhp) as well as the two six-cylinder
versions BMW 320i (92 kW/125 bhp) and BMW 323i (102 kW/139 bhp). A
sports suspension was optionally available from factory for all four
versions. Also, alloy wheels were on offer as an alternative to the
standard 14-inch steel rims. The wheels, which were larger compared to
those featured on the predecessor model, offered sufficient room for
larger dimensioned brakes. New floating-calliper brakes replaced the
previously employed fixed-calliper design and a larger brake power
assist unit was added. The BMW 323i was once again fitted with disc
brakes all round. The front disc brakes were - as on the BMW 320i -
ventilated. Improved stability thanks to ABS and four-wheel drive. For
the first time, an optional electronic anti-lock brake system (ABS) was
available for the six-cylinder versions. Initially, BMW had employed
this innovative safety feature on the BMW 7 Series, but only a short
while later the premium technology was utilised for the high-output
versions BMW 323i and BMW 320i. Sensors for wheel speed, a control unit
and a hydraulic unit automatically controlled wheel slip and wheel
acceleration in such a way as to prevent the wheels from locking in
hazardous situations. This also ensured that both stability and
steerability were maintained when the brakes were applied, even on
slippery surfaces and in bends. From 1992, this feature was standard on
all BMW 3 Series models. The modified rack-and-pinion steering
provided better tractability and increased precision on uneven road
surfaces. The power steering technology already employed on the
six-cylinder versions of the predecessors was now available for all
models as an option. In the year 1985, the top-of-the-range model was
toppled from its leading position by the 126 kW/171 bhp six-cylinder
model BMW 325i, which then already featured ABS as standard. At the
same time the BMW 325iX, the version with the best traction and
four-wheel drive, was launched. Right from the start, BMW engineers
were not satisfied with simply an on-demand front-wheel drive. In fact
the transfer gearbox with automatic viscous locks permitted
ABS-compatible and permanent four-wheel drive. This resulted in
optimised traction in all road conditions and the highest degree of
stability in every motoring situation. In normal operation 63 percent
of power was transferred to the rear axle and 37 percent to the front.
So power transmission had very little effect on the steering. Hence the
BMW 325iX convinced through exceptionally harmonious driving behaviour.
Inspired by motor sports, geared to performance: the BMW M3. Finally, at
the 1985 International Motor Show in Frankfurt, the spotlight focused
on a further newcomer that set the pulse of many a motor sports
enthusiast racing - the first BMW M3. Developed on the basis of the
two-door BMW 3 Series Saloon and powered by a 147 kW/200 bhp
four-cylinder engine, an uncompromising sports car had entered the
scene. The first chapter of an unrivalled success story, that has
lasted to this day, had been written. Not only was the BMW M3's power
unit inspired by motor sports, but also its suspension technology. For
instance, axle kinematics, springs and dampers were extensively
modified and adapted to racing standards and to the high engine
performance. The brake system with ABS as standard comprised internally
ventilated brake discs at the front and an engine-driven high pressure
pump. This servo pump simultaneously supplied power to the steering, so
that both systems operated independently from negative engine pressure.
In the model year 1987, the M3 was also the first BMW to offer
electrically adjustable dampers. The driver could choose between
"Sport", "Normal" and "Comfort" using a
rotary switch located next to the handbrake lever. Control lamps on the
dashboard indicated which setting had been selected. 1990: The third
generation of the BMW 3 Series - more agility, enhanced precision and
electronic slip control. The third BMW 3 Series generation made its
first appearance in October 1990, featuring boldly elongated contours
and thoroughly revised technology. At the time of its launch a choice
of two four-cylinder and two six-cylinder versions was made available.
The BMW 316i served as an entry version with an output of 74 kW/100
bhp, the BMW 318i delivering 83 kW/113 bhp, and the two straight
six-cylinder versions featured in the BMW 320i and the 325i mustered 110
kW/150 bhp and 141 kW/192 bhp respectively. The long 2,700-millimetre
wheelbase and the elongated body made a promise of sheer driving
pleasure and the chassis also came well up to expectations. The third
generation of the BMW 3 Series ran on a single-joint spring strut axle
with transverse stabilisers at the front, and now featured a rear axle
with a central control arm and two transverse control arms arranged on
top of each other for optimised stability particularly in bends,
harmonious running characteristics and enhanced suspension comfort.
Both front and the rear axles were fitted with double-pipe gas pressure
dampers. For the first time engineers had designed the rear track to be
wider than at the front. This structural design remained in use for the
model generations that followed. Power assisted steering for the even
further developed rack-and-pinion steering was now a standard feature
on the BMW 318i. For the first time the driver was not only able to
adjust the seats individually, but also adjust the steering column
axially in order to find his or her ideal position behind the wheel.
An M technology sports suspension lowered by15 millimetres was available
as an option. The wheels, either steel or light-alloy, depending on the
model, had increased in size to 15 inches. The effectiveness of the
brakes was also increased even further. The four-cylinder models
featured disc brakes at the front combined with drum brakes on the rear
wheels, the six-cylinder versions being fitted with disc brakes all
round, including internally ventilated discs at the front. The
top-of-the-range model, the BMW 325i, came with ABS as standard, further
versions offering this state-of-the-art system initially as an option
and, as from 1992, as a standard feature. In addition, Automatic
Stability Control (ASC) was included in the range of optional
equipment. Irrespective of the driver's accelerator pedal input, the
anti-slip control system permitted only a limited amount of engine
power to be conveyed to the drive wheels in each respective driving
situation to prevent the wheels from spinning. From 1997, the enhanced
form of this technology termed ASC+T, with additional braking
intervention for stability, was available for all BMW 3 Series models.
The new edition of the BMW M3, which was based on the BMW 3 Series Coupe
and launched in 1992, also impressed with further enhanced dynamics
resulting from the newly developed 3-litre straight six-cylinder power
unit with an output of 210 kW/286 bhp as well as an entirely
re-engineered suspension. The single-joint spring strut front axle was
complemented with reinforced spring seats and axle stubs. And the new
central-arm rear axle was, inter alia, adapted to the high engine
output through the addition of modified longitudinal arms. Furthermore,
dampers and stabilisers were now significantly firmer. These
modifications were also reflected in the body height: The BMW M3 was
precisely 31 millimetres lower than a BMW 3 Series Coupe. The so-called
compound brakes at the front were a further highlight. Due to the
compound construction comprising an aluminium brake-disc chamber and a
grey cast iron friction ring, the disc was able to expand without
distorting as the brakes were applied. Thanks to its dynamic and
superior handling characteristics, the new BMW M3 set standards
internationally in terms of sportive driving pleasure. Hence it was,
for example, voted "Best Handling Car" by experts from the US
car magazine "Car and Driver". 1998: The fourth generation
with a consistent lightweight construction and innovative stability
control systems. BMW developed a newly conceived lightweight suspension
and innovative stability control systems for the fourth generation of
the BMW 3 Series. With its basic construction and its technical
highlights, the suspension technology reached a level previously only
found on luxury class automobiles. The proportion of aluminium used on
the suspension was now around 60 kilograms, i.e. 20 percent of the
overall weight. Moreover, a further optimisation was achieved through
the selective use of high-strength steel on front and rear axle
supports. The overall construction was significantly lighter than that
of the previous model and facilitated a further increase in agility. In
addition to the distinctively increased body stiffness, the familiar
even axle load distribution contributed towards the harmonious, stable
and constantly controllable handling characteristics of the BMW 3
Series. The fourth BMW 3 Series generation had a 25 mm longer
wheelbase and a 60 mm wider track than its predecessor. The elongated
body contours distinctively reflected the saloon's sporting character,
driving dynamics even directly benefiting from its further reduced
aerodynamic resistance. With regard to kinematics and
elasto-kinematics, the central-arm rear axle with double-pipe gas
damper and stabiliser corresponded to the construction of the previous
model. The use of high-strength steel for the rear axle improved
vibrational behaviour, and a double-elastic rear suspension with rubber
mountings provided additional comfort. In addition, the well-proven
concept of a single-joint spring strut suspension with transverse
stabilisers at the front was developed even further and complemented,
inter alia, with a hydraulically damped transverse arm mount. With the
exception of the BMW 328i, which featured 16-inch alloys as standard,
all variants of the fourth BMW 3 Series generation stood on 15-inch
rims. During the years that followed a variety of light-alloy rims in
various sizes up to 18 inches were available as an option. As in the
case of the predecessor, power assisted steering was again included in
the list of standard features and, for the first time, the steering
column could not only be adjusted axially, but also in height.
Premiere for groundbreaking stability control systems: CBC and DSC. Once
again, a significant advancement had been achieved with regard to brake
and stability control systems. All fourth-generation BMW 3 Series models
were fitted with disc brakes all round. Their degree of effectiveness
was optimised by ABS, which was now also a standard feature. BMW also
introduced the Cornering Brake Control system (CBC), a further
development of ABS and a technology that facilitated optimal
utilisation of the rear axle braking force, but without having an
adverse effect on tracking stability. It is the also task of the system
used on current BMW models to counteract the vehicle's tendency to
drift inwards if the brakes are applied when driving round bends at high
speeds. CBC identifies the situation and ensures that the vehicle is
stabilised by means of a controlled build-up of braking force to each
individual wheel. This counteracts the tendency to oversteer.
Likewise, the anti-slip control system ASC + T was again included in the
range of standard features on all BMW 3 Series vehicles. Dynamic
Stability Control (DSC) was a brand new technology initially only
available for the 328i as an option. This innovative system was
designed to rapidly and accurately identify any possible adverse
effects on the vehicle's stability by measuring the yaw rate and
lateral acceleration and to prevent oversteer or understeer
particularly in bends by means of appropriate intervention. In this way
it became possible to re-establish vehicle stability by means of
targeted brake intervention on individual wheels as well as through a
reduction in engine power. DSC has been a standard feature on all BMW 3
Series models since 2001. As early as 2000 it was possible to equip
both the 3 Series Saloon and the 3 Series Touring with the new version
of BMW four-wheel drive technology. Permanent power transmission to all
four wheels was linked to the Dynamic Stability Control system. In this
manner it was possible to achieve a traction-enhancing locking effect
by means of brake intervention on each individual wheel. The new
all-wheel technology was offered in combination with six-cylinder
engines. There was a choice of the variants 330xi, BMW 325xi and BMW
330xd. New BMW M3 with variable M differential lock. The optimisation
of the suspension system featured on the new generation of BMW M3s -
again developed on the basis of the BMW 3 Series Coupe and presented in
2000 - also managed to keep pace with technical advancement in the field
of drive technology. The BMW M3's new straight-six cylinder engine now
delivered 252 kW/343 bhp, and thanks to high engine speeds and a
comparably short axle transmission, it developed enormous power that
had to be safely and consistently converted into driving dynamics.
The high-performance sports car profited from the exceptionally stiff
body structure of the BMW 3 Series, its even axle load distribution and
the weight-optimised suspension construction. In addition to individual
suspension components, both the compound brake system and the effect of
the Dynamic Stability Control system (DSC) were adapted to match the
outstanding performance of the high-revving power unit. Furthermore,
the new version of the torque-sensitive differential lock system
already employed on previous models offered improved traction in the
event of the vehicle being driven in a demanding fashion. The variable
M differential lock responded exceedingly sensitively to the varying
friction values on the drive wheels. Depending on the driving
situation, a variable locking value of between 0 and 100 percent could
be produced. This ensured consistent optimum traction under all load
requirements, irrespective of the road surface. 2005: The fifth
generation - with the best suspension in its segment. With the market
launch of the fifth model generation 30 years after its success story
had begun, the BMW 3 Series celebrated a spectacular anniversary in
2005. BMW engineers had been successful in again bringing the
suspension technology a noticeable step forward, virtually bringing it
in line with the characteristics of the drivetrain and car body. This
resulted in better agility and more driving fun for the customer.
Thanks to a convincing and harmonious concept, the BMW 3 Series was able
to further strengthen its profile within its segment. The new symbiosis
of powerful engines, dynamic and cultivated driving characteristics,
the distinctive styling with the typical BMW design language, a
torsionally stiff, generously dimensioned body and innovative equipment
features was a huge international success right from the word go. Just
a year after the market launch, the new BMW 3 Series was awarded the
title "World Car of the Year" in New York. Current BMW 3
Series models boast the largest and most varied range of engines ever
made available for the series. There is a choice of five petrol and five
diesel engines, both for the Saloon and the Touring model. Four petrol
and four diesel engines are available for the BMW 3 Series Coupe,
whilst the BMW 3 Series Convertible comes in four petrol and three
diesel versions. Output ranges from 105 kW/143 bhp for the BMW 318i to
225 kW/306 bhp for the BMW 335i. All-wheel drive - known as BMW xDrive
technology with electronically controlled, variable power distribution
between front and rear wheels for enhancing stability, traction and
driving dynamics - is available for the Saloon, the Touring and, now
for the first time, the Coupe. Innovative axle designs. The fifth BMW
3 Series generation also has a larger chassis than its predecessor. The
wheelbase has increased by 35 mm and track width by 29 mm. Depending on
the model version, equipment and loading condition, the load on the
rear axle is between 48 and 56 percent, this being practically the ideal
value for even weight distribution. The design of the front axle has
once again been derived from technology developed for the luxury class.
The constructional concept comprising an axle with double-joint tension
rod and spring struts corresponds to the principle used for the BMW 5
Series. Tension rods, transverse control arms, swivel bearings and
front axle support are made entirely of aluminium, a lightweight
concept with which BMW has made a particularly consistent advancement. A
high degree of stiffness and weight optimisation are combined in a
unique manner. Both characteristics have a positive effect on the
vehicle's agility. The five-link rear axle featured by the BMW 3
Series has been completely redesigned. The unique construction offers
ideal preconditions for a particularly dynamic behaviour. With five
individual control arms for each wheel, virtual kinematic points can to
a large extent be freely determined. The large supporting base for
track and camber on the wheel carrier side, extremely rigid control
arms, the stiff rear axle support and the connection to the car body
via pushrods facilitate elasto-kinematics that provide across a broad
spring travel range precisely the wheel control necessary for superior
vehicle handling in any situation. Furthermore, due to small and
effective lever arms, the rear axle is hardly affected by negative
influences and facilitates outstanding rolling characteristics. In
addition, a well-balanced coordination of springs and dampers enhances
the BMW 3 Series' agile character. Depending on the model variant, the
BMW 3 Series comes with 16-inch or 17-inch wheels as standard. The
tyres have emergency running properties - likewise a standard feature
and unique in this segment - that allow the journey to be continued
even in the event of a total pressure loss. A tyre defect indicator
notifies the driver as soon as the pressure loss in a tyre exceeds 30
percent. Disc brakes all round and ABS with the CBC Cornering Brake
Control system are standard features. All BMW 3 Series variants are
fitted with internally ventilated discs at the front, six-cylinder
versions and the BMW 320d additionally at the rear. Apart from the high
degree of effectiveness, a weight-optimised construction was taken into
account when developing the brake system. The continuous brake lining
wear indicator, that also calculates the remaining mileage, also
enhances safety and comfort. State-of-the-art vehicle stability
control with new functions. The Dynamic Stability Control feature for
the fifth-generation BMW 3 Series now has a significantly broader
functional range. The stabilising effect achieved by means of brake
intervention on each individual wheel and a reduction of engine power
has been complemented by numerous other possibilities of enhancing
safety and comfort in demanding driving situations. These include
Automatic Stability Control (ASC), trailer stability control and
Dynamic Brake Control (DBC), which automatically maximises brake force
on both axles should it detect that the driver wishes to brake as hard
as possible. Moreover, the special mode Dynamic Traction Control (DTC)
can be selected at the push of a button, a feature that raises the
response threshold of the DSC system. This facilitates better starting
off on snow or loose sand and renders possible particularly sporty
driving behaviour and high lateral acceleration levels in bends. The
DSC system featured in BMW 3 Series six-cylinder models also includes
additional functions. By means of a systematic increase in brake
pressure, the decrease in stopping power known as fading is prevented
in the event of exceptionally high brake temperatures. Regular dry
braking optimises brake performance in wet weather. With the brake
readiness function moderate brake pressure is built up as soon as the
driver takes his foot off the accelerator pedal. This guarantees
spontaneous brake response. Furthermore, a hill-start assistant
facilitates easier hill starts by preventing the vehicle from rolling
backwards for a defined period of time. Steering: Precise, efficient
and more dynamic thanks to Active Steering. Typical BMW characteristics
such as driving pleasure, driving comfort and driving safety owe their
existence to a considerable extent to the targeted precision of the
steering and the accurate response given to the driver. With the
exception of the BMW 335i and the BMW 335d, which are equipped with
rack-and-pinion steering with hydraulic power steering technology, all
BMW 3 Series variants feature electro-mechanical steering EPS (Electric
Power Steering), which also includes the speed-dependent Servotronic
steering assistance system. EPS features a steering assistant which
operates by means of an electrical actuator that can be utilised when
required. The steering assistance system is only activated if it
becomes necessary or if the driver wishes. During constant travel
straight ahead the electrical actuator has no output. Hence EPS, an
integral part of the BMW EfficientDynamics programme, is making a
contribution towards a further reduction in the BMW 3 Series'
consumption and emission levels. Active Steering, which is optionally
available for the BMW 3 Series, provides enhanced precision and
steering comfort. In addition to the steering assistance system or
Servotronic respectively, Active Steering varies the steering ratio
according to driving speed. At low speeds a larger steering angle is
effectuated than at higher speeds, but with the same amount of steering
wheel movement. Consequently, less effort is required when parking the
vehicle, for example. Within the medium speed range Active Steering
enhances the BMW 3 Series' agile character. In contrast, at higher
speeds it aids directional stability. Additionally, Active Steering
adopts a stabilising effect in particularly demanding driving
situations. In the event of braking manoeuvres on uneven surfaces
(µ-split braking), the directional stability is maintained
through targeted and restrained counter-steer.