Chassis and suspension: From damping to shift programs - Technology for a unique driving experience

Apr 22, 2009
  • Shock absorbers: selective control as standard
  • Dynamic handling package: damping system with two modes
  • Brakes: ADAPTIVE BRAKE with useful additional functions
The newly developed AGILITY CONTROL suspension with standard-fit amplitude-dependent damping system forms the basis for the further enhanced ride comfort and agile handling of the E-Class Coupé. The shock absorbers adapt to the current driving situation, reducing the damping forces automatically when driving normally with low shock-absorber impulses and increasing the forces up to the maximum as required when cornering at speed or performing evasive manoeuvres. In this way, the chassis and suspension meet stringent requirements in terms of road roar, tyre vibration and agility - without ever compro-mising on active safety.
What's more, the longer wheelbase (an extra 45 millimetres), wider track (an extra 33 and 70 millimetres respectively) as well as the positioning of the engine low down and far towards the rear make a fundamental contribution to the new, agile driving experience by producing a favourable centre of gravity. The even axle load distribution ensures an almost perfect balance between the front and rear axles, as well as improved traction and handling stability.
The data at a glance:
 
New E-Class Coupé
Preceding model
Track*, front/rear
1538/1544 mm
1505/1474 mm
Wheelbase
2760 mm
2715 mm
Turning circle
10.95 m
10.76 m
Axle load distribution*, front/rear
52.1 %/47.9 %
52.9 %/47.1 %
*Based on the example of the E 250 CGIBlueEFFICIENCY Coupé
Shock absorbers: adjustment of the damping forces in line with the current driving situation
The AGILITY CONTROL shock absorber system - fitted as standard - is purely hydromechanical and requires no sensors or electronics. The core components are a bypass channel in the shock absorber's piston pin and a control piston moving within a separate oil chamber. When linear travel of the shock absorber is low, the control piston forces oil through the bypass channel to produce a significantly smaller damping force at the actual damper valve. The resulting, "softer" shock absorber characteristic translates into a high level of ride comfort. If the excitation of the shock absorber is greater, the control piston moves to its limit position so that oil ceases flowing through the bypass duct, meaning that the full damping force is available.
Mercedes-Benz has enhanced the three-link front suspension with McPherson struts in a number of different respects, achieving excellent results in terms of ride comfort in particular. In the interests of favourable axle kinematics, superior vibration characteristics and enhanced safety, the lower link level consists of two separate elements which act as torque and cross struts. As well as offering more precise wheel location, this design has the particular advantage of compensating vibrations caused by tyre imbalance and fluctuating braking forces better than rigid wishbones. It also provides longer deformation paths in the event of a frontal collision. The third front-axle link is the track rod which connects the transversely installed steering gear to the wheels.
The spring struts consist of cylindrical, transverse force-compensating coil springs, double-tube shock absorbers and newly developed three-phase head bearings. In order to further optimise ride comfort, a starkly upright position has been chosen for the spring strut so as to reduce the forces acting on the torque strut bearing. As a consequence, it was possible to reduce the bearing rigidity, which has a positive effect on the chassis' tyre/road contact characteristics and rolling characteristics - for example when driving over expansion joints running across the road. The anti-roll bar is connected to the spring strut, which is likewise actively involved in locating the front wheels.
Intelligent use of aluminium and steel reduces the weight of the front axle by twelve percent compared to the outgoing model. The forwards-slanting torque struts and the cross struts are made of aluminium.
Subframe: robust high-strength-steel construction
The front-axle components, steering gear, engine and transmission are pre-mounted on a high-strength-steel subframe which is bolted securely to the bodyshell's side members, making it a key component in the front crash structure of the new Coupé: in the event of a frontal impact, the subframe forms a separate load-bearing path along which the impact energy is absorbed at specific points. The stiffness at the connecting points between the subframe and the body where load is transferred as a result of the forces and vibrations produced by the chassis and suspension has been increased substantially, all of which translates into more agile and more precise handling.
Steering: more direct for agile handling
The Mercedes Coupé's AGILITY CONTROL suspension is complemented by a likewise newly developed rack-and-pinion steering system. This operates with a ratio of 14.5, and is therefore around seven per cent more direct than on the outgoing model. Positioning the steering gear 80 millimetres in front of the wheel centre makes for predictable self-steering characteristics with a slight tendency to understeer.
The steering gear housing and valve body are made of aluminium, while the rack is forged from high-strength steel. Thanks to further optimisation of all components with respect to installation space and weight, the steering gear is around 0.8 kilograms lighter than the version in the outgoing model.
Drivers can adjust the steering column to their liking within a height adjustment range of +/- 25 millimetres and a reach adjustment range of 35 millimetres - well in excess of the standard in this vehicle category. A fully electrically adjustable steering column is included if the optional Memory package is ordered.
To greatly enhance occupant safety, the steering column has been designed to collapse telescopically by up to 100 millimetres when hit by the driver with a certain degree of force in the event of a frontal collision. This extended deformation path reduces the forces exerted on the driver's head and chest area.
As an optional extra, Mercedes-Benz also offers speed-sensitive power steering. This adapts the power assistance to the vehicle speed: the lower the speed, the greater the assistance. Up to a speed of 200 km/h the steering effort is continuously reduced as a function of vehicle speed, which means that only one third of the maximum steering effort is required when parking at slow speed. Variable centring is another new feature adopted from the S-Class: the electro-hydraulic speed-sensitive servo valve is used to generate a centring moment that increases with the speed and gives a secure and stable feeling in the straight-ahead position. At slow speeds, this additional steering moment is not activated, so the benefits of the power steering can be exploited to the full.
The power steering pump features an electrically controlled solenoid valve which controls a bypass opening and, as a result, allows metering of the oil quantity in line with requirements. This setup reduces the pressure and oil quantity when driving straight ahead, for example – the power steering pump operates with a substantially reduced output and, consequently, helps to save fuel.
Rear axle: further developed multi-link independent suspension
Mercedes-Benz's multi-link independent suspension, which has proven itself time and again over a period spanning more than 25 years, has been further modified for use in the new E-Class Coupé in order to meet more stringent requirements in terms of comfort and agility. Modified components include the subframe, subframe carrier, struts and hub carriers/steering knuckles. In keeping with the lightweight design concept, wheel location components such as struts, hub carriers and the metal sections of the elastomer bearings are largely made of aluminium. The rear-axle subframe is made of high-strength steel.
Optional equipment: sports suspension and dynamic handling package
Alongside the standard-fit AGILITY CONTROL suspension with adaptive damping system, the new E-Class Coupé offers two further options for adapting the suspension to the driver's individual requirements. One of these optional extras is the AGILITY CONTROL sports suspension with sports-tuned speed-sensitive power steering, stiffer springs, tauter shock absorbers and stronger torsion bars. When cornering or performing evasive manoeuvres at speed, this sporty suspension tuning translates into noticeably lower body roll.
Further optional equipment available includes a dynamic handling package developed specially for the E-Class Coupé (standard for the E 500 Coupé), which solves the classic suspension-tuning trade-off by offering a choice of two modes: Sport or Comfort. These modes allow continuously-variable electronic control of the shock absorbers based on seven sensor signals.
The system adjusts the damping force for each wheel individually and fully automatically, depending on the current road conditions and driving situation. When driving normally on poor road surfaces, a soft damper setting is selected to give the occupants maximum comfort while maintaining excellent handling stability and safety. If the driver decides that more brisk progress is called for, however, the shock absorber settings are continuously adapted to meet the need for more dynamic performance.
The driver can pre-program the principle vehicle characteristics at the push of a button. In Sport mode, the hydraulic forces of the shock absorbers are increased so as to allow even better directional stability and road adhesion at high speeds as well as reduce understeer at speeds of up to 120 km/h.
Speed-sensitive sports steeringwith variable centring is also part of this package. To enhance agile handling, the steering ratio has been reduced from 14.5 to 13.5; the steering torque is increased at speeds above 80 km/h to provide a more sporty steering feel. Furthermore, the system adjusts the accelerator pedal characteristics in Sport mode in order to ensure more spontaneous engine response. If the Coupé is fitted with an automatic transmission, the gear-change characteristics are also altered, while the gear-change times are shorter and the driver can change gear even more quickly by using the shift paddles on the steering wheel.
Body Index: outstanding agility without compromising on ride comfort
In order to allow comparison of the suspension characteristics, Mercedes engineers have developed the "Body Index" concept - a composite formula for handling dynamics, which is calculated from the readings for various typical driving manoeuvres. The Body Index is an indication of how well the suspension is linked to the body, how closely the car hugs the road and how nimble the handling is through fast bends. In other words, how taut the suspension settings are. The higher the figure, the sportier, i.e. firmer, the suspension characteristics.
The Body Index for the E-Class Coupé with AGILITY CONTROL suspension fitted as standard is 2.0; this figure is around ten percent higher than that for the out-going model and, thanks to adaptive shock absorber control, is achieved without compromising on ride comfort. If the Coupé is equipped with the dynamic handling package, the Body Index is between 1.89 (Comfort) and 2.06 (Sport).
Brakes: with Hill-Start Assist, Hold function and brake drying function
With the ADAPTIVE BRAKE, the E-Class Coupé offers an innovative braking system incorporating additional assistance functions for enhanced comfort and safety. One example of this is the practical HOLD function: after the two-door model has been braked to a standstill, briefly pressing the brake pedal a little further is all that is required to activate this function. The car is then held by the brakes, even if the driver's foot comes off the brake pedal. In this way, the ADAPTIVE BRAKE prevents the car from rolling forwards inadvertently when stopped at traffic lights or stuck in stop-and-go traffic and from rolling backwards when facing up a slope. The HOLD function is deactivated automatically when the car moves off.
If the driver's foot moves abruptly from the accelerator to the brake pedal before an emergency stop, the brake system increases the pressure in the brake lines and brings the pads into contact with the brake discs so that maximum braking power is available as soon as the driver hits the brake pedal. This priming of the brakes allows the system to assist the standard-fit Brake Assist system.
The ADAPTIVE BRAKE enhances safety in the wet by sending brief braking pulses at regular intervals to remove the film of moisture from the brake discs, allowing the brakes to work to full effect. This automatic brake drying function is always activated when the windscreen wipers have been operating for a certain time; the driver never even notices these precisely metered brake pulses. Finally, the ADAPTIVE BRAKE assists the driver with hill starts. If the sensors detect that the car is stopped on an uphill slope, a hill-start-assist function is activated automatically, maintaining a constant brake pressure for a brief period to prevent the car from rolling backwards. The driver therefore has enough time to move their foot from the brake pedal to the accelerator without having to use the foot-operated parking brake.
Brake discs: larger and even more effective than before
Large front and rear brake discs provide an ideal technical basis for ensuring safe and reliable deceleration in any driving situation. The front and rear discs measure up to 344 millimetres and 300 millimetres in diameter respectively, depending on the engine version.
Brake data and dimensions at a glance:
Front
E 250 CGI BlueEFFICIENCY Coupé
E 250 CDI BlueEFFICIENCY Coupé,
E 350 CDI BlueEFFICIENCY Coupé,
E 350 CGI BlueEFFICIENCY Coupé
E 500 Coupé
Brake calliper

Brake disc

Diameter/thickness
Single-piston floating

Internally ventilated

295 mm/28 mm
Single-piston floating

Internally ventilated

322 mm/32 mm
Single-piston floating*
Internally ventilated and perforated
344 mm/32 mm

Rear
 
 
 
Brake calliper

Brake disc

Diameter/thickness
Single-piston floating

Solid

300 mm/10 mm
Single-piston floating

Internally ventilated

300 mm/22 mm**
Single-piston floating
Internally ventilated

300 mm/22 mm
* Composite aluminium and nodular-cast-iron design;
**10 mm for E 250 CDI BlueEFFICIENCY Coupé
 
 
For brake cooling, the Mercedes engineers have developed two-section aluminium cover plates which have been tested in the wind tunnel and ensure that, whilst driving, the cool air flows from the underbody into the wheel arches and, finally, to the brake discs.
Control systems: electronics for safe motoring
When it comes to active safety systems too, the E-Class Coupé features an array of state-of-the-art technology as standard, including anti-lock brakes, acceleration skid control, Brake Assist and the Electronic Stability Program. For ESP®, Mercedes-Benz has developed control logic that offers the driver even more effective assistance in critical cornering situations: precisely measured brake pulses sent to up to three wheels cause a moderate reduction in the car's speed and help it to turn safely into bends.
ESP® Trailer Stabilisation, which is activated if the Coupé is equipped with a trailer coupling, detects dangerous oscillating movements of the trailer and restabilises it automatically by sending precisely measured brake pulses to the front wheels of the towing vehicle. If the danger is even more acute, the system applies the brakes to reduce the car's speed automatically whilst reducing the engine torque before the precisely measured brake pulses are sent to the wheels to stabilise the trailer.
As an option, Mercedes-Benz can equip the Coupé with a pivoting trailer coupling, whose ball head needs to be neither fitted nor removed again. Instead it pivots away beneath the body together with its electrical socket, so that it is concealed from sight when not in use. The E-Class Coupé has a maximum trailer load of up to 1800 kilograms (braked).
The Electronic Stability Program monitors the tyre inflation pressure too, and warns the driver if there is a sudden loss of pressure in one of the tyres. To this end, the system continuously compares the rotational wheel speeds, which mainly depend on the vehicle speed, vehicle load and tyre pressures. The control unit also consults other dynamic ESP®sensor readings, such as the lateral acceleration, yaw rate and wheel torque, to help it diagnose tyre pressure loss. The system is therefore able to detect any deviations, and informs the driver accordingly via the central display.
To ensure continued mobility in the event of a flat tyre, Mercedes-Benz also offers run-flat tyres as an option. These are available in 245/45 R 17 format and feature self-supporting sidewalls, enabling Mercedes customers to continue driving for a distance of up to 50 kilometres at a maximum speed of 80 km/h, depending on the vehicle load.
Wheels and tyres: 16-inch wheels as standard
The range of wheels and tyres for the new E-Class Coupé offers a wealth of personalisation options. Mercedes customers have a choice of wheel and tyre combinations in 17- or 18-inch format. The four-cylinder models are equipped with 16-inch nine-spoke light-alloy wheels and 215/55 R 16 tyres as standard. As a no-cost option, Mercedes-Benz can also supply 205/55 R 16 tyres with extremely low rolling resistance and special light-alloy wheels whose weight has been reduced by a total of 9.6 kilograms thanks to sophisticated forging technology.
Mercedes-Benz equips the V8 Coupé with 235/40 R 18 front tyres and 255/35 R 18 rear tyres as standard.
Mercedes-Benz E-Class Coupé with steel spring suspension system.
09A248
Mercedes-Benz E-Class Coupé with steel spring suspension system.
09C336_07
Mercedes-Benz E-Class: The three-link suspension with McPherson spring struts that Mercedes-Benz has enhanced further in various aspects.
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Mercedes-Benz E-Class: Mercedes-Benz has again improved the details of the multi-link independent rear suspension for the new E-Class.
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