Newly developed chassis technology creates the basis for the agile yet comfortable handling characteristics of the new C-Class Estate. Mercedes engineers defined this driving profile during the early development phase and geared all measures towards achieving it.

The longer wheelbase (an extra 45 millimetres), wider tracks (an extra 36 and 68 millimetres respectively), as well as the positioning of the engine low down and far towards the rear make a fundamental contribution to the new driving experience by producing a favourable centre of gravity. Moreover, 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 key data for the chassis at a glance:

*taking example of C 220 CDI, EC kerb weight incl. driver

 

AGILITY CONTROL - this is the term used by Mercedes-Benz for all new and further developments that improve both comfort and agility in equal measure. Foremost among these is the AGILITY CONTROL suspension, which is standard equipment in both the C-Class Saloon and Estate. It is based on an amplitude-dependent damping system: when driving normally with low shock absorber stimulus, the damping forces are automatically reduced for a noticeable improvement in ride comfort - but without any compromise in handling safety. When shock absorber stimuli are of greater magnitude, for example when cornering at speed or taking evasive action, the maximum damping forces are set and the car is stabilised effectively.

This technology is purely hydromechanical and requires no complex sensors or electronics. The key 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 shock absorber is subjected to greater stimulus, the control piston moves to its end position so that no more oil flows through the bypass channel. This makes the maximum damping force available.

Accordingly, this shock absorber technology plays an important role in the agile yet comfortable driving characteristics of the new C-Class Estate. One indication of this is the maximum body roll angle when cornering, which has been reduced by as much as ten per cent compared to the outgoing model courtesy of the AGILITY CONTROL suspension - without any loss of comfort.

The AGILITY CONTROL suspension of the C-Class is complemented by a likewise newly developed rack-and-pinion steering system. This operates with a ratio of 14.5, and is therefore six 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 and valve housings are of aluminium, while the steering rack is of forged, high-strength steel, as a result of which it weighs 0.8 kilograms less than in the previous C-Class.

The height and reach-adjustable steering column also has a special, new feature which proves beneficial in the event of a frontal collision: when impacted by the driver, the steering column telescopes together with a controlled level of force to reduce the loads acting on the upper body. This increases the deformation path by up to 100 millimetres.

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 the driver 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.

Mercedes-Benz has enhanced the three-link front suspension with McPherson struts in a number of different respects. In the interests of favourable axle kinematics, superior vibrational comfort and improved safety, the lower link level consists of two separate elements which act as torque and cross struts and are both forged from aluminium. In addition to precise wheel location, this design has the particular advantage of compensating vibrations caused by tyre imbalances or fluctuating brake forces better than rigid wishbones. It also provides longer deformation paths in the event of a frontal collision.

The third component in the three-link system is the track rod, which connects the transversely installed steering gear with the wheels. The reinforced stabiliser is linked to the spring strut, which is likewise actively involved in front wheel location. The struts consist of cylindrical coil springs counterbalanced by lateral forces, twin-tube shock absorbers and newly developed, three-phase head bearings. If the body rolls severely, the stabiliser is supported by rebound buffer springs. The result is agile handling accompanied by a high level of comfort.

The front axle components, steering gear, engine and transmission are pre-mounted on a what is known as the subframe. This is made from high-strength steel and is bolted to the side members of the bodyshell, which makes it a major element of the crash structure at the front end. During a frontal collision, the subframe creates a separate load dissipation path which effectively absorbs the impact energy. The connecting points between the subframe and the bodyshell have been substantially reinforced, and therefore have a higher initial rigidity to counter the forces and vibrations generated by the suspension. This can be appreciated as more agile, more precise handling.

The career of the multi-link independent suspension began with the launch of the Mercedes-Benz 190 in 1983, and it still remains unsurpassed in many respects. Accordingly this patented suspension concept is also retained in the new C-Class, albeit in a fully redeveloped and therefore greatly improved form. Modifications have been made, for example, to the subframe and its bearings, which are now supported by the bodyshell on two levels by means of an additional strut. The primary benefits of these new developments and enhancements are reduced weight as well as improved ride and vibrational comfort.

The multi-link independent suspension principle is based on research examining the best possible movement characteristics for the rear wheels of a passenger car. If one regards the wheel in isolation, i.e. without any axle linkages, it has six possible movements available to it: it can push or pull in a vertical or horizontal direction, and it can turn in three directions. The aim of suspension engineers is to prevent such uncontrolled independence, however, and to limit the free movements of the wheel so that it can only move along a precisely defined spatial curve. Accordingly they have attached the wheel to five flexibly mounted, independently acting control arms which restrict five of the available spatial movements:

1. The lower transverse control arms activate the suspension springs and dampers

2. The upper transverse control arms regulate the camber over the spring travel

3. The torque struts take up the drive and braking forces, and compensate for dive and squat when accelerating and decelerating

4. The diagonal struts are arranged differently from the torque struts, and likewise help to prevent dive and squat when braking and accelerating

5. The track rods limit changes in the wheel’s toe-in to a desirable minimum

Owing to this intelligent control arm construction, each rear wheel basically retains freedom of movement in one plane only: namely during controlled compression and rebound.

In addition to the standard AGILITY CONTROL suspension, the new C-Class Estate offers two other ways of adapting the suspension characteristics to drivers' individual preferences. Firstly, there is the options of a sports suspension with shorter springs, firmer shock absorber settings and thicker stabiliser bars. The suspension is furthermore lowered by 15 millimetres. When cornering at speed or swiftly switching lanes, this sporty suspension configuration brings about a noticeable reduction in body roll of around 35 per cent, compared to the preceding model with sports suspension. Vertical vibrations - an indicator for long-distance comfort - are reduced by around 20 per cent too.

Secondly, Mercedes-Benz has developed a dynamic handing package which offers drivers a choice of two shift programs: Sport and Comfort. Within these two programmes the shock absorbers are subject to infinitely variable electronic control. A total of seven sensors monitor the current driving situation and relay their information to an electronic control unit, which then calculates the optimum shock absorber characteristic. Depending on the current road or operating conditions, the system adjusts the damping forces for each individual wheel - variably and fully automatically, for even more ride comfort and individuality. When driving normally on poor road surfaces, a soft damper setting is selected to maximise occupant 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 wish for more dynamic performance.

The driver is able to predetermine the basic vehicle set-up by pressing a button on the dashboard. Two settings are available: "Comfort" and "Sport". In Sport mode, the hydraulic forces of the shock absorbers are increased to achieve yet greater handling stability at high speeds and reduce the inherent understeer at speeds up to 120 km/h, for example. If this package is specified, the suspension is lowered by 15 millimetres and features shorter springs and thicker stabiliser bars. The newly developed speed-sensitive steering with variable centring is also included. In the interests of agile handling, the steering ratio has been reduced from 14.5 to 13.5. In Sport mode, the system also adapts the accelerator characteristics for more spontaneous engine response. And on models equipped with an automatic transmission, the shift characteristics are modified and the shift times shortened too.

The dynamic handling package also includes a three-spoke steering wheel and – on automatic models - shift paddles on the steering wheel.

In order to clearly illustrate the performance characteristics of the different suspension variants, the engineers at Mercedes devised the body index. This is calculated from the readings for various typical driving manoeuvres, making it a sort of new composite formula for a vehicle's dynamic handling abilities.

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 short, it shows how firm the suspension tuning is. The higher the body index reading, the sportier - i.e. the firmer - the suspension characteristics.

The standard AGILITY CONTROL suspension gives the C-Class a body index of between 1.91 and 2.01 hertz. With the dynamic handling package fitted, meanwhile, the C-Class attains values ranging from 1.96 to 2.46, taking it into sports car territory. By way of comparison: the Mercedes-Benz SLR McLaren has a body index of 2.94, providing clear evidence of just how dynamically the C-Class can move if the driver so wishes. This sports-car-like agility is down to the suspension technology with its continuously adjustable shock absorbers.

For the self-levelling suspension that is available as an option, Mercedes-Benz employs an automatically pumping hydropneumatic system, in which all components are fully integrated into the rear shock absorbers. Quite apart from saving space and weight, this arrangement dispenses with the hydraulic and electric lines that were previously needed. The shock absorber houses an oil reservoir, pressure reservoir, pump, height sensor and control mechanism, along with the damper unit.

The energy required for levelling out the suspension is derived while the vehicle is on the move from the relative movements between the axle and body. In this way, the system is able to maintain full compression and rebound travel, steady ground clearance, optimum axle kinematics and a constant natural body frequency, regardless of the vehicle load.

The new Estate also offers state-of-the-art from the luxury class when it comes to braking technology - cue ADAPTIVE BRAKE. This system provides additional support functions for even more safety and comfort. One example is priming of the braking system in critical situations: when the driver switches abruptly from the accelerator to the brake pedal prior to emergency braking, the system increases the pressure in the brake lines and brings the brake pads into light contact with the brake discs, so that they are then able to bite immediately and with full force when the brake pedal is depressed. In this way, the system complements the functions of the standard Brake Assist.

ADAPTIVE BRAKE also has safety benefits in the wet: the system briefly applies the brakes at regular intervals to wipe the film of water from the brake discs and ensure that the brakes are able to perform at their peak. This automatic brake drying function is always activated when the windscreen wipers have been operating for a certain length of time. The finely metered brake pulses are imperceptible to the driver.

Finally, the braking system also helps the driver with hill starts. When the sensor system detects that the Estate has come to a stop on an uphill gradient, a hill-start assist function is automatically activated which keeps the brake pressure constant for a brief period to prevent the car from rolling backwards. This gives the driver enough time to switch from the brake to the accelerator pedal without having to first engage the parking brake.

Generously dimensioned front and rear brake discs create the technical basis for safe, reliable deceleration. Depending on the engine version, they have a diameter of up to 322 millimetres at the front and up to 300 millimetres at the rear. A tandem brake booster unit which has now been enlarged to eight inches in size ensures a standard of responsiveness and operating comfort that lives up to all expectations.

Data and dimensions of the braking system in the new Estate at a glance:

With the anti-lock braking system (ABS), acceleration skid control (ASR), Brake Assist (BAS) and the Electronic Stability Program (ESP®) all included as standard, the C-Class Estate is as up-to-date as ever where driving safety systems are concerned. The engineers at Mercedes have extended the functions of these systems and made detailed technical improvements. ESP®, for instance, now features a new control logic which assists the driver even more effectively in critical cornering situations: by triggering precisely metered braking pulses at up to three wheels, the Estate is made to turn safely into bends with only a moderate drop in speed.

A further additional function of the Electronic Stability Program improves safety when towing a trailer. The new ESP® trailer stabilisation function, which is activated on models equipped with a trailer coupling, detects if the trailer is weaving from side to side dangerously and automatically brings it safely back on course by

means of selective braking pulses at the front wheels of the towing vehicle. If the danger is more acute, the system first automatically reduces the road speed by braking whilst throttling back the engine torque, before proceeding to stabilise the trailer with selective braking pulses.

As an option, Mercedes-Benz can equip the C-Class Estate 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 new Estate has a maximum trailer load of up to 1800 kilograms (braked) - a benchmark value for this model class.

The Electronic Stability Program monitors the air pressure in the tyres 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 optional extra. These tyres have self-supporting walls, and enable Mercedes customers to continue for a distance of up to 50 kilometres at a maximum speed of 80 km/h, depending on the vehicle load.

The range of wheels and tyres available provides a great deal of scope for equipping the new Estate to the customer’s personal taste. The wheel/tyre combinations at a glance:

 

Further wheel/tyre combinations are available ex factory as optional extras.