AMG sports suspension and high-performance braking system: Perfect blend of driving dynamics, ride comfort and active safety

Sep 7, 2010
The Direct-Steer system, Torque Vectoring Brake and crosswind stabilisation are the three new systems now available as standard on the CL 63 AMG. In combination with the AMG sports suspension and AMG high-performance braking system, these unique high-tech systems provide the highest level of driving dynamics, ride comfort and active safety.
Less steering effort, more agile handling with the same outstanding straight-line stability – the Direct-Steer system in a nutshell, which is now fitted as standard
to the CL 63 AMG. A key feature of the Direct-Steer system - which is well-known in the S 63 AMG - is the variable-ratio steering rack that operates using purely mechanical means. While the power steering around the central position utilises an indirect ratio to promote excellent straight-line stability, this alters from a steering angle of around five degrees: really small steering angles are all it takes to perform precise cornering, noticeably improving handling on winding country roads. The steering angle requirements have also been modified, enabling the driver to steer the AMG Coupé far more easily, particularly on urban roads. Compared with a steering system with a constant ratio, the number of revolutions from lock to lock is reduced by around 25 percent with the Direct-Steer system.
Another advantage of the purely mechanical Direct-Steer system is the absence of any elaborate actuators and additional sensors – with associated benefits in terms of weight, installation space and susceptibility to faults. The constant steering
response is also advantageous compared with other variable steering systems that sometimes require the driver to adapt quickly to what are fast changing situations on the road.
The Direct-Steer system is based on the familiar speed-sensitive power steering system which reduces the power assistance as the road speed increases. Easy
manoeuvrability on urban roads where large steering angles and thus a great deal of power assistance is required, is coupled with reduced support at high speeds, say
on the motorway – all of which improves straight-line stability and handling safety.
Torque Vectoring Brake optimises driving dynamics and handling safety
A further improvement in driving dynamics as well as active handling safety comes courtesy of the Torque Vectoring Brake, which is now also fitted as standard on the CL 63 AMG (not on the S 63 AMG). If the Electronic Stability Program ESP® detects the onset of understeer, short one-sided braking intervention on the vehicle's inside rear wheel generates a specific yawing moment around the vehicle's vertical axis within a fraction of a second. Consequently, the coupé handles precisely and remains under control at all times as well as also bolstering active handling safety by reducing the tendency to understeer.
Automatic crosswind stabilisation as standard
The AMG sports suspension based on Active Body Control (ABC) now also comes with automatic crosswind stabilisation in the CL 63 AMG. The ABC control electronics vary the wheel load distribution so that the effect of crosswinds is virtually compensated for or reduced to a minimum. If the coupé is affected by a crosswind, the ABC control unit utilises the yaw-rate, lateral acceleration, steering angle and speed sensors of the Electronic Stability Program ESP® to trigger diagonal wheel load distribution instantly – for instance on the left front and right rear wheel. The associated steering effect reduces the effect of the crosswind. Crosswind stabilisation is activated at speeds above 80 km/h while travelling in a straight line or on slight bends. The function is deactivated if the driver himself makes heavy, brusque steering corrections.
Based on Active Body Control (ABC), the AMG sports suspension all but entirely eliminates the body movements that occur in both high-performance vehicles when moving off, cornering and braking. Bends are negotiated with far less roll; the body roll caused by fast evasive manoeuvring is effectively suppressed. Other notable features of Active Body Control are the variable roll moment distribution between the front and rear axles, which the system carries out automatically according to the speed. The computer uses various acceleration sensors to obtain information on the current driving situation and compares this data with those from the pressure sensors in the spring struts and the level sensors on the control arms. The system then computes the control signals that the servo-hydraulic valves at the front and rear axle transform into precisely metered flows of oil.
Briefly pressing the Sport button next to the AMG instrument cluster changes the characteristics of the AMG sports suspension: the roll angle through fast corners is reduced further, the shock absorbers and springs also respond firmer to promote agility. At speeds of between 65 and 100 km/h, ABC automatically lowers the body by as much as 15 millimetres to reduce wind resistance. If more ground clearance is needed when driving on poor road surfaces, the level of the vehicle can be raised by 40 millimetres at a speed up to 30 km/h by simply pressing a button.
Thanks to so-called loading adjustment, the active suspension control also takes the current vehicle weight into account as part of its calculations. As such the S 63 AMG and CL 63 AMG are able to achieve identical levels of driving dynamics when in a laden condition too.
AMG high-performance braking system based on ADAPTIVE BRAKE
Based on the ADAPTIVE BRAKE system, the AMG high-performance braking system continues to set the benchmark for stopping power, sensitivity and fade resistance. The front axle of both models features a double floating brake calliper. This technology combines the advantages of a sliding-calliper disc brake – reduced heat transfer to the brake fluid and clear advantages in terms of comfort thanks to the brake lining guide mechanism – with the efficiency of an extra large fixed calliper brake. At the rear, braking is handled by large sliding frame-type callipers. Internally ventilated, perforated composite brake discs at the front and rear with a diameter of 390 and 365 millimetres respectively ensure the shortest stopping distances, remarkable resistance to fading and outstanding sensitivity.
The hydraulic dual-circuit braking system is controlled electronically, permitting the inclusion of numerous driver assistance functions that improve safety and comfort – such as "priming" the braking system in critical situations: if the driver suddenly switches from the accelerator to the brake pedal before emergency braking, ADAPTIVE BRAKE increases the pressure in the brake lines and applies the pads to the brake discs, so that they can grip instantly with full force when the brake pedal is pressed. In wet weather, the system injects regular, short brake impulses to ensure that the film of water on the brake discs is wiped off and the brakes can work as effectively as possible. This automatic brake-drying function is always activated when the windscreen wipers have been in operation for a certain time; the driver does not notice the finely metered braking impulses.
After the S 63 AMG and CL 63 AMG have been braked to a standstill, briefly pressing the brake pedal a little further is all that is required to activate the HOLD function. The vehicle is then held by the brakes, even if the driver's foot comes off the brake pedal. In this way ADAPTIVE BRAKE prevents the car from rolling forward inadvertently when stopped at traffic lights or stuck in stop-and-go traffic, and from rolling back when facing a slope. The HOLD function is deactivated automatically when the car moves off.
Attractive light-alloy wheels featuring a new AMG triple-spoke design
AMG light-alloy wheels, featuring a new triple-spoke design and painted in titanium grey with a high-sheen finish, provide the contact with the road on both the S 63 AMG and the CL 63 AMG. The 8.5 x 19 wheels at the front are fitted with 255/40 ZR 19 tyres, while 275/40 R 19 tyres are combined with 9.5 x 19 wheels at the rear.