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Chassis and Suspension
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The Chassis and
Suspension of the BMW M6: Agile, Fast, Safe
The chassis and
suspension of the BMW M6 is based on the all-aluminum chassis of the
BMW 6 Series suitably modified in its kinematics to the increase in
engine power. Naturally, the very stiff bodyshell as well as the
large number of aluminum components provide the ideal foundation for
sheer driving pleasure at its best. Added to this there is the
perfect balance of weight spread out on the front and rear axles
and, of course, rear-wheel drive typical
of BMW and keeping the steering free of drive forces.
The M6 retains the basic
geometry of the 6 Series suspension: Track measures 1,567
millimeters or 61.7创 at the front and 1,584 millimeters or 62.4创
at the rear, wheelbase is 2,781 millimeters or 109.5创. Featuring an
increase in negative camber, wheel guidance and control meets the
even greater
demands made in terms of driving dynamics and high loads.
Axle load distribution
in perfect harmony is again typical of BMW, with 54 per cent of the
car's weight on the front, 46 per cent on the rear axle. Added to
this there is the unladen weight of only 1,710 kilos or 3,771 lb (ECE),
combining ideal dimensions and ideal weight in a particularly
dynamic blend. So with the BMW 6 Series already offering the perfect
rendition of agility and dynamic performance, the BMW M6 enhances
this driving pleasure to a significantly higher standard than you
initially might deem possible.
Intelligent lightweight
technology: Less mass - but extra strength and stiffness.
With the exception of components such as the tiebars, wheel mounts
or bearing journals subject to high loads, the two-arm spring strut
front axle is made completely of aluminum. The U-shaped front axle
subframe takes up the steering mechanism, anti-roll bar, track
control arms and pushrods.
A multi-dimensional
aluminum frame gives the front axle subframe maximum crosswise
strength and stability, offering the advantage of particularly
precise response to the steering.
The aluminum frame comes
complete with two NACA intakes of the same type as used in
motorsport or aviation. These openings allow cooling air to flow
through the front section to the transmission and other components
without impairing the aerodynamic and streamlining qualities of the
underfloor.
Servotronic with two
control maps
In developing the BMW M6
High-Performance Coupe, the engineers at
BMW M GmbH have given particular attention to the steering system
crucial to agile and safe motoring. Via special control maps,
Servotronic steering management controls the degree of power
assistance as a function of road and engine speed. This solves the
basic conflict of interest between high power assistance for
comfortable parking and low assistance in the interest of superior
driving dynamics at high speeds.
Two different
Servotronic control lines corresponding to the EDC mode
currently in use allow two different configurations, one focusing on
motorsport, the other on motoring comfort. In the former case with
the sports-oriented control line, the steering is very direct giving
the driver precise feedback under high lateral acceleration. This is
important because of the extremely high speeds the M6 is able to
reach in a bend. The comfort setting, in turn, places the emphasis
on motoring comfort appreciated above all on long distances.
A common feature shared
by both map control lines is that they maintain the basic
characteristics and feeling of the steering.
Rear axle perfectly
set-up in intelligent lightweight technology
Made almost completely
of aluminum, the Integral IV rear axle in the BMW 6 Series - a
configuration absolutely outstanding in terms of both directional
stability and comfort - has been adapted to the car's far higher
level of performance through special elastokinematics as well as
reinforced arms, guide bars and joints. The former rubber-dampened
wheel guidance joints, for example, are replaced by rigid, solid
joints offering a far higher standard of stability in the interest
of even more precise wheel guidance. This also reduces temperatures
in the final drive by up to 15 癈 versus a conventional
configuration, dramatically cutting back the thermal load acting on
the axle components.
The final drive is
connected to the SMG transmission by a two-piece propeller shaft
featuring a Hardy disc at the front, a synchronizing joint at the
rear, and a central bearing. The output drive shafts are made as
torsionally stiff hollow pipes in the interest of minimum weight.
M Differential Lock for
more driving pleasure and extra safety
Like the BMW M3 and M5,
the two other models in the BMW M Family, the M6 comes with its
final drive comprising a variable, speed-sensing M Differential
Lock. This gives the Coupe superior driving stability and optimum
traction particularly when accelerating out of a bend.
A differential lock
serves to build up locking action whenever required, for example if
one of the two drive wheels threatens to spin. Such a differential
lock is appreciated particularly by the sports-minded driver since
it further enhances the advantages of rear-wheel drive on roads with
an average or above-average frictional coefficient, where the driver
prefers a sporting, dynamic style of motoring.
Superior traction in winter.
On a "normal"
torque-sensing differential lock the overall drive power transmitted
to the wheels depends on the momentum and forces conveyed by the
wheel running on the more slippery side with a lower frictional
coefficient. Wherever this frictional coefficient is particularly
low, for example on snow, gravel or ice, the traction benefits
offered by a conventional lock concept are limited by the restricted
support forces. BMW's Variable M Differential Lock, on the other
hand, offers a decisive advantage in terms of traction even in very
demanding situations, for example with the wheels running on totally
different surfaces with a very significant difference in their
frictional coefficient.
In combination with the
carefully set-up DSC system and the well-balanced axle load
distribution, this gives the M6 very good driving characteristics in
winter weather.
A further advantage of
the Variable M Differential Lock lies in the fact that the system
immediately builds up increasing locking action with an increasing
difference in the speed of rotation on the two drive wheels. As a
result, the wheel under less load - for example the inner wheel in a
bend on a fast serpentine road - can no longer cause the drive
forces conveyed to the wheels to "collapse". Instead, the wheels
consistently retain their drive forces and traction on the road.
Up to 100 per cent
locking action
BMW's Variable M
Differential Lock incorporates a shear pump spontaneously building
up pressure as soon as the drive wheels start to run at a different
speed. This pressure is transmitted via a piston to a multiple-plate
clutch conveying drive forces to the wheel with better grip as a
function of the difference in speed. In an extreme case all the
drive power coming from the engine may be transmitted to the wheel
with a better frictional coefficient.
As soon as the
difference in speed between the two wheels starts to decrease, pump
pressure is reduced accordingly and locking action is cut back. This
self-adjusting pump system is maintenance-free and is filled with
highly viscous silicon oil.
Benefiting from this
advanced technology, the driver of the BMW M6 is able to set off
much better and more smoothly on surfaces varying significantly in
their frictional coefficient, since the wheels have far better
traction.
The Variable M
Differential Lock also improves the car's handling and driving
stability in the interest of extra safety and driving pleasure.
M Generation DSC for
extra safety
The outstanding driving
dynamics and safety offered by the car's chassis and suspension may
be optimized to an even higher standard in specific situations by a
control system which intervenes when needed. BMW integrates these
control systems within the overall concept of Dynamic Stability
Control specially configured for the BMW M6.
The task of these
systems is to permanently monitor driving conditions and
to intervene in the interest of extra stability wherever required.
So it is fair to say that DSC is a special safety function taking
the car and the driver to the very limits of physics.
Wherever necessary, DSC
intervenes as required in engine management, reducing drive forces
and/or activating the brakes on each wheel.
The result is a higher
standard of driving safety, for example on slippery roads, in abrupt
maneuvers, or with the car starting to lose stability in a bend.
The special M Generation
of DSC developed for the BMW M5 and M6 enables the driver to
pre-select the dynamic driving programs in the MDrive mode, and then
call up the program required via the MDrive button in the steering
wheel. While the first stage of DSC in this case is basically the
same as in the BMW 6 Series, the M Dynamic Mode is intended for the
very dynamic, sports-oriented driver.
M Dynamic Mode - an
outstanding achievement in driving dynamics
The M Dynamic Mode (MDM)
sets a new standard in driving dynamics, offering the sports-minded
and ambitious driver a revolutionary improvement in dynamic
performance: This special sub-function of DSC reserved to BMW M Cars
enables the driver to capitalize on the car's longitudinal and
lateral acceleration by pressing the MDrive button in the steering
wheel.
The driver using this
option is quite literally limited only by the extreme laws of
physics. DSC intervenes only when the car is driven to the absolute
extreme, thus allowing the driver to countersteer moderately while
power-sliding through a bend at a controllable angle. Clearly, this
means that the M Dynamic Mode should be used only on a race track
closed to public traffic.
A warning sign in the
instrument panel informs the driver that the
M Dynamic function is active. And there is also a warning signal
informing
the driver as soon as he deactivates the DSC function altogether.
EDC: From taut and
dynamic all the way to comfortable and smooth
Adjusting Electronic
Damper Control, the driver is able to set the characteristics of the
chassis and suspension as required from taut and sporting all the
way to comfortable and smooth. This is done by the three Comfort,
Normal and Sports programs selected via the MDrive button in the
steering wheel or the push button next to the SMG shift lever. For
all practical purposes, therefore, the driver is able to convert his
BMW M6 at the touch of a button into a thoroughbred driving machine,
a sports car for everyday use, and a luxury coupe for grand touring
in grand style.
EDC ensures ongoing,
infinite control of electronic damper forces over a very wide range
of different settings. In the Normal program damper forces are
automatically adjusted as required to specific driving conditions.
The system provides an optimum combination of motoring comfort and
driving safety.
The driver then has the
option to pre-select the Comfort or Sports programs, varying damper
characteristics accordingly. In the Sports mode the chassis and
suspension respond to bumps on the road and uneven surfaces by
building up higher damper forces to reduce body motion and give the
M6 a much firmer grip on the road. In the Comfort mode, by contrast,
EDC reduces damper forces in the interest of a higher level of
motoring comfort. In bends, when applying the brakes and when
accelerating, higher damper forces enhance driving safety in all
modes, improving body sway and dive behavior of the M6 accordingly.
A further benefit is the consistent maintenance of good vibration
characteristics regardless of the load the car is carrying
throughout its complete lifecycle.
High-performance brakes
like in motorsport
Reflecting its
outstanding performance, the BMW M6 comes with extra-large
high-performance brakes featuring weight-optimized compound brake
discs carried over directly from motorsport. Optimum arrangement and
configuration of the holes drilled into the brake discs ensure
excellent stopping power both in the dry and under wet conditions.
Brake disc dimensions
are 374 x 36 millimeters (14.72 x 1.42创) at the front and 370 x 24
millimeters (14.57 x 0.94创) at the rear. The aluminum double-piston
swing calipers, optimized for low weight and enhanced stiffness,
significantly reduce unsprung masses and contribute accordingly to
the car's agility, safety and comfort on the road. As a result, the
BMW M6 offers stopping distances otherwise seen only in motorsport,
coming to a halt from 100 km/h (62 mph) within just 36 meters or 118
ft, and from 200 km/h (124 mph) within less than 140 meters (459
ft).
Diagnostic system
measuring brake pad wear
Determining brake pad
wear at specific measuring points, a sensor transmits the data
monitored to the DSC control unit. Then, as a function of the
driver's style of motoring, the system determines the current state
of the brake pads and forecasts the remaining mileage until the
brake pads have to be replaced. This information is used for
Condition Based Service in order to determine meaningful and
appropriate service dates.
The wheels - simply
outstanding in their looks and technical features
The wheels on the BMW M6 are extra-large from the start due to the
large brake discs. In terms of their looks, in turn, the19-inch
forged aluminum wheels developed exclusively for the BMW M6 give the
car even greater presence and appeal on the road. With their five
contoured double-spokes, these wheels not only look delicate, but
are 1.8 kilos lighter than conventional cast aluminum wheels.
Like the wheels, the car's tires do not come off the rack, but were
rather developed exclusively for BMW M in an elaborate series of
tests: The front tires measure 255/40 ZR 19, the rear tires are
285/35 ZR 19. In their rubber compound and dimensions, the tires are
designed to precisely convey high lateral and longitudinal forces
with a relatively high standard of roll comfort on both dry and wet
surfaces. They also offer appropriate feedback to the driver,
allowing the car to be pushed to its physical limits whenever,
without sacrificing safety in the process.
Tire repair system takes
the place of a spare wheel
The tire repair system
comes complete with BMW's Tire Pressure Indicator as well as the
second-generation M Mobility System. Providing both a visual and
acoustic signal, the Tire Pressure Indicator warns the driver of a
sudden or gradual drop in pressure in one of the tires.
Featuring appropriate
hump geometry, the rims prevent even an empty tire with zero
pressure from "jumping off" the wheel, thus allowing the driver to
safely stop the car in the event of a puncture. The M Mobility
System then serves to seal holes in the tire of up to 6 millimeters,
allowing the driver to proceed safely to the next workshop.
This means that in
practice the driver is able to repair virtually all punctures
without having to change the wheel right away, so that the BMW M6
does not require a spare or emergency wheel. The result is a
decrease in weight of more than 20 kilos compared with a full-size
spare wheel, obviously helping to improve the car's power-to-weight
ratio and driving dynamics.
5. Body, Design,
Equipment: Light and Safe, Sporting and Luxurious.
The body of the BMW 6 Series offers all the qualities and features
required
for the M6: The body dimensions are perfectly suited for
accommodating the ten-cylinder and all its ancillaries, without
requiring any major modifications. Likewise, the innovative body
structure with its efficient combination of steel, aluminum and
plastics offers everything required to match the enhanced power and
performance of the BMW M6. So that in a nutshell, the term
"intelligent lightweight construction" is most appropriate in this
context.
Lean and clean: Optimum
blend of materials
"Intelligent lightweight
construction" means using the right material at the
right place. On the BMW 6 Series and in the M6 in particular, the
weight-reduced front section of the car cuts back overall weight by
approximately 45 kg or 99 lb versus a conventional steel structure
at the front. The spring supports resting in the front axle and
dampers are made of a pressure-cast aluminum alloy, just as the
doors and hood are made of aluminum. The front fenders, in turn, are
thermoplastic; the rear lid is made of a sheet molding compound. And
last but not least, tailored rolled blanks also help to save weight
by gearing the metal plates and panels used precisely to specific
requirements at each point.
Despite the very good
starting point already provided by the "basic" 6 Series, the
objective in developing the M6 was to shed all further weight not
absolutely essential in the interest of supreme agility and
handling. But this was not to detract from the car's comfort,
roominess, and everyday motoring qualities.
Losing weight gram-by-gram for sharper agility.
Following this
philosophy, the engineers at BMW M were able to reduce the weight of
the M6 by a few more kilos. The improvement of axle load
distribution and the car's center of gravity achieved this way
significantly enhance the agility of the M6 on the road. Dry weight
is limited to a mere 1,785 kilos or 3,936 lb (ECE). But when it
comes to active and passive safety, the M6 naturally retains all the
qualities of the "basic" 6 Series without any restrictions.
Roof made of
carbon-fiber, the No 1 material in Formula1
The engineers at BMW M
have saved more than 4.5 kilos on the M6 by giving this new Sports
Coupe the same kind of roof as on BMW's already legendary M3 CSL, a
purist driving machine successfully setting standards in lightweight
technology. Like the M3 CSL, the M6 comes with a roof made of
carbon-fiber, a high-tech material carried over from Formula1.
Carbon-fiber-reinforced plastic (CFP), to use the full term, has a
density of approximately 1.5 kg per cubic decimeter, as opposed to
2.7 kilos per cubic decimeter in the case of aluminum.
By comparison,
conventional steel is four times heavier than carbon-fiber, weighing
approximately 7.8 kilos per cubic decimeter. Every kilo saved
especially on the roof has a very positive effect on the car's
driving dynamics. With the weight of the roof being reduced by 50
per cent versus a conventional steel structure right at the "top"
where it really counts, the car's center of gravity is lowered
accordingly. The benefit for the customer is higher speed in bends
and further reduction of body dive and roll.
Innovative production
technologies also in series production
To provide a
particularly attractive eye-catcher demonstrating the close
connection between BMW's large coupe and motorsport, the use of
carbon on the roof of the M6 is clearly visible from outside. A
further advantage provided by the carbon roof is the ability to use
a particularly light and thin rear window. And unlike the "regular"
6 Series, the roof as a whole is not welded, but rather bonded, on
to the body of the car, while still retaining full body stiffness
and safety, with the same noise and temperature management as on the
6 Series as such.
BMW builds the
carbon-fiber roof in-house, lightweight construction experts at the
Landshut Plant making the roof out of several layers of this
precious material initially pre-formed in dry state, then soaked in
resin in a resin transfer molding (RTM) process, and finally treated
with a layer of clear topcoat. Contrary to theM3 CSL built only in
very small numbers, the CFP roof on the BMW M6 marks the first use
of this technology in series production.
Less weight at the ends
for enhanced agility and handling
The bumper supports
front and rear are also made of CFP in a unique
process developed by BMW and applied at the Landshut Plant. In this
process unparalleled the world over, strips of CFP are woven
layer-by-layer around
a core, cast into resin and hardened before the core material is
subsequently removed. This provides an extremely light but highly
stable hollow-profile
support which, in its function and effect, is quite comparable to a
conventional support made of steel or aluminum. The weight saving of
20 percent at the front and 40 percent at the rear where such a
reduction in weight really counts significantly enhances the car's
agility and handling, providing higher speeds above all in bends.
Kilos per horsepower -
the formula for the performance athlete
All the efforts made to
save weight are ultimately confirmed by a good power-to-weight ratio
stating what mass (weight) the engine is ultimately required
to accelerate. While the mass of a car can be matched in terms of
longitudinal dynamics (acceleration and deceleration) by adding
extra power and using even more efficient brakes, a reduction of the
car's overall mass improves both longitudinal and lateral
acceleration at the same time. In practical terms, therefore, a
lighter car is faster in a straight line, achieves higher speeds in
bends, and requires shorter stopping distances. Hence, the
power-to-weight ratio of a car says much more about its driving
dynamics than just the power or torque rating.
The BMW M5 Sports Sedan boasts a power-to-weight ratio of 3.5 kg:bhp,
making it the benchmark in its class. Now, benefiting from its
design and consistent lightweight technology, the M6 Coupe is
another 45 kilos or 99 lb lighter than the M5. Featuring the same
engine, therefore, BMW's Sports Coupe comes with a sensational
power-to-weight ratio of only 3.3 kg:bhp. This makes the BMW M6 one
of the absolute leaders in the high-performance sports car market.
Efficient cooling - a
particular challenge
The supply and
extraction of cooling air is a particular challenge in motoring,
above all with a car of this caliber. This is why the BMW M6 comes
with an all-new cooling and air supply package featuring a
high-performance fan, engine radiator, a/c capacitor, power steering
fluid cooler and engine oil cooler all positioned directly behind
the car's front air dam. For reasons of the car's package, in turn,
the engine oil cooler is fitted at an angle in front of the radiator
and the radiator itself is split up into two sections.
The large air openings
in the front air dam for cooling and intake air are
particular eye-catchers. The side openings to the left and right of
the
large central air scoop, in turn, ensure efficient intake of
secondary air flowing to the engine of the BMW M6.
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