dynamics + suspension
W163 M-Class
Body on frame versus unibody chassis
Mercedes engineers discussed for many months whether a body on
frame or unibody chassis would be more suitable for the M-Class.
While body-on-frame chassis provide better noise, vibration and
harshness (NVH) insulation they are somewhat heavier.
A unibody requires softer rubber in the independent suspension elements
to achieve similar NVH performance, compromising on-road
handling. A frame also improves side impact protection and encloses
the fuel tank and exhaust, and is more durable. To reduce the weight
penalty to between 50 to 90 lbs the frame can be integrated with the
bumpers front and rear, the tow hook, and with independent
suspension anchor points, which also lowers the center of gravity
2 inches. Thus the M-Class uses a welded Krupp steel box section frame
with two longitudinals and three cross members, typically employed in
Mercedes off-roaders and heavy duty vehicles. For the successor, however,
a unibody chassis was selected. Some of the newer such designs have no
weight advantage, and large ones may even be heavier than a similar sized
frame based vehicle, depending to some extent on the desired capabilities.
However, the new W164 M-Class is about 200 lbs lighter although the exterior
dimensions increased, but not quite as light as the lean early model years
of its W163 predecessor.
Mercedes-Benz |
The front and rear suspension of the W163 M-Class is similar. Both are using a double wishbone layout with stabilizer bar and rearward steering gear or track rod. The wishbones are forged aluminum for the upper front and upper and lower rear, and the lower front control arm forged steel. Top: front axle with torsion bar connected to lower control arm. Bottom: rear axle with coil springs or hydrostruts. |
S-class pioneers M-class front suspension geometry
The C111 experimental vehicles in the early 70s pioneered the
front suspension geometry of the M-class. On the first Mercedes-Benz
officially called S-Class, the W116 series from 1971 to 1980, this
technical innovation was introduced for the first time as standard,
the double-wishbone front suspension with zero-offset steering and
anti-dive control. The handling and steering characteristic of
this geometry contribute to make it a real Mercedes-Benz. And like
in the W140 S-class the suspension was built onto a subframe, to
further reduce noise, vibration and harshness.
M-Class springs, shocks, suspension struts
Rollovers induced with the corkscrew ramp
From ABS to ESP®
From ABS braking, four wheel electronic traction system, 4ETS, to the
ESP electronic stability program and SBS Sensotronic brake system. ESP®
first appeared in 1995 in the twelve cylinder models, and due to its
popularity is now standard on all Mercedes.
 Skaters |
Mechanical ESP |
ESP® arctic testing |
ESP® valves |
 S600 coupé with ESP |
Stability for Mercedes models
These estimates can be used to compare the relative stability of
some sedans, cabrios and off-road vehicles.
The M-Class four wheel drive: 4ETS
is a four wheel drive system which automatically directs power to
gripping wheels. It's a permanent four-wheel drive with three open
differentials. It's a pretty elegant and user-friendly design.
Some prefer it over older mechanical systems like manually
operated lockers, hydraulically actuated multi-plate clutches (old
4Matic), Torque-sensing on-demand systems, electrically actuated wet
clutch packs, limited slip differentials, viscous couplings or Haldex
clutches. These systems may be better suited
for low speed work than performance driving and cross country rallies.
4ETS is used in many new performance vehicles like the E-class 4Matic
sedans and wagons, M-class, the Mercedes C-class and S-class,
the Mercedes Grand Sport Tourer and next generation M-class and
G-class. Since it appeared in 1997 it has proven itself, even on
the toughest cross country rallies in the world, like the
world cup.
M-Class electronic traction system with new functions, ETS+
Mercedes-Benz Multi-link independent rear suspension
More than 20 years ago Mercedes developed a milestone in rear axle
technology, the multi-link independent rear suspension. It's produced
at Mettingen and has become an unsurpassed technological success. This
construction incorporates an ingenious technological device to solve a
basic rear axle problem. In all rear wheel drive vehicle there are
three main points of force: driving power at acceleration in driving
direction, braking power when halting against driving direction, the
side-force when cornering. At each of the straining points of these
forces, force lever arms are created which would cause rear wheel
instability. Note, however in the case of multi-link independent
rear suspension, to eliminate the force lever arms the force transducer
points of the transverse links would have to be exactly at the wheel
center plane. But the brake disk is in the way. Therefore the
transverse links are each divided into two stabilizer links. Their
imagined centerline cross at the wheel plane center so the effect is
the same as if the transducer points would actually be there.
Neither axial forces nor side-forces can influence the rear wheel and
and cause off-center angles. However, true driving comfort is only
created with flexible bearings of the stabiliser links. This
tribute to driving comfort has a serious disadvantage. Flexible
bearings give way under force and other force lever arms are created.
The wheels are thus off-center despite geometrically true links.
On the multi-link independent rear suspension the links are constructed
in such a way that their centerlines cross further outside.
So far outside that the link angle becomes zero.
M-class (W163) with Twin-Tube Dampers
The classic twin-tube damper used in the W163 M-class has the
advantages of low friction, high ride comfort, multi-step piston and base
valve allow variation in characteristic curves and short length.
Did you know that the Bilstein gas shock absorber world
premiered in 1957 on a Mercedes?
Hydropneumatic suspension: Fichtel & Sachs flying carpet
The hydropneumatic suspension at all four wheels was introduced
around 1977 with the 6.9 and was optional on the European 500 SEL
starting in 1979, option code 487. Fichtel & Sachs supplied the struts.
The nitrogen spheres need to be renewed every 10 to 15 years when
the ride becomes bouncy. Pulling a manual lever on the dash raises
the clearance by 1 to 2 inches and also hardens the ride somewhat.
It was a rare option, only 1000 per year were ordered, and it cost
$3,890. It was discontinued when the new S-Class came out in 1992.
Automatic rear level control
is a $940 factory option on the 1992-1999 W140 S-Class, standard
on the S500 and S600 using two hydrostruts. It was also installed in
1986-1991 W126 560SELs, and wagons.
Adaptive Damping System (ADS)
ADS was introduced as factory option for the new S-Class in 1992
and was standard on the 1995 S600. As factory option it cost $2,270 to $2,670.
The front shock absorber contains two electric valves which can
alter the damping using 4-levels. Rear damping is changed by two
electric valves in the hydraulic line between the suspension strut
and the nitrogen sphere, in vehicles with rear level control.
An earlier version with adjustable shocks controlled by a lever on the
steering column was used in the 600 Mercedes (1964-1981) together with
self-leveling air suspension.
ADS front shock schematic
V12 über alles: Understanding and Diagnosing the ADS System
Active Body Control (ABC): a quantum leap forward in chassis technology
Engineers at Daimler-Benz have been focusing on active body
control since 1978. They found an ideal partner in the chassis
specialists at ZF Sachs. First developed and tested extensively for
the CL 500, introduced in 2000, then the 2001 S 55 AMG and S 600.
ABC struts control an interior upper spring seat hydraulically in
real time, every few milliseconds. Option code 487.
ABC schematic
SmartBar
is an electronically actuated stabilizer module designed to maximize
off-road articulation. SmartBar disengages the stabilizer bar, allowing
full wheel travel on rough terrain. The system can be driver and/or
automatically activated. Or one can manually disconnect the torsion bar
when off-road, since it limits articulation. Or use a semi-active suspension,
which ties air reservoirs per axle when offroad to simulate - and outperform
- solid axles.
The F400 Carving: "Dynamic systems designed for the cars of tomorrow and beyond"
The Mercedes F400 Carving research car, introduced at the Tokyo auto
show in 2001, achieves a lateral acceleration of 1.28 g, that's
28% more than conventional sports cars, by tilting the wheel axles.
AIRMATIC (Adaptive Intelligent Ridecontrol)
ThyssenKrupp Bilstein developed the new air suspension
in combination with 4-level adjustable ADS dampers for the 2000+ S-Class
together with engineers from DaimlerChrysler and Phoenix.
Airmatic combines air suspension and ADS 2.0 into one unit including
automatic levelling at each wheel. The extremely thin wall thickness
of the airbag using
250 polyamid fibers with 0.38 mm thickness ensures low internal dynamic
wall stiffness of the strut which characterizes the roll comfort of the tire.
Some Airmatic struts develop leaks. A repair kit became available.
AIRMATIC DC (dual control)
The suffix "DC" stands for "Dual Control" and refers to the dual
function of AIRMATIC: the system combines an actively controllable air
suspension with the Adaptive Damping System (ADS II), thereby influencing
both springing and damping in equal measure and was introduced on the
Maybach. It unites two otherwise opposite suspension characteristics,
hard in corners for good cornering capability and comfortable otherwise
by automatically controlling air volume sizes and offers driver selectable
sport modes. Standard on the 2003 to 2006 E 500 and optional on other
E-classes for $1600.
AIRMATIC DCX (dual control cross-country)
further enhances AIRMATIC by increasing the variable ride
height when off-road. The larger volume also softens the
suspension off-road and further increases the articulation.
The clearance can be increased by several inches.
Skyhook control
With the so-called skyhook algorithm the damping forces at each
wheel are controlled in such a way that the wheel-induced forces acting
on the vehicle body are reduced, and the automobile body behaves similar
to being attached to a hook in the sky.
4 wheel air suspension
The GL-Class introduces standard 4 wheel air suspension. The small
ADS 2.0 modules attached in parallel to the lower air suspension
strut are optional with the offroad package.
New Mercedes adaptive shock absorber premiers on A-Class
A new dynamic and comfortable shock absorber premiered on the
new W169 A-Class. It autoselects between sporty and comfortable settings
hydraulically, without complex control electronics. Made with ThyssenKrupp Bilstein's
new Tailored Orbitals process.
Mercedes-Benz article
New C-Class with Agility Control
Tenneco supplies their continously controlled electronic suspension (CES)
for the new C-Class and GLK, the Agility Control System, which dynamically
adjusts to road conditions and driver actions.
created in 1998 and updated from time to time
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