Suspension and brakes: Sure-footed both on and off the road

Jun 24, 2019
Stuttgart/Salt Lake City

Already the base version of the new GLS (except in USA/Canada) offers the newly developed AIRMATIC air suspension system with Adaptive Damping System Plus (ADS+). A special highlight is the optional E-ACTIVE BODY CONTROL suspension, which is based on a 48V on-board power supply and represents an innovation in suspension engineering with the highest standard (see subsequent separate chapter). The braking systems for the new GLS have also undergone an evolutionary improvement and are far more powerful. Wheels with diameters of up to 23 inches for the AMG Line are yet another new suspension feature in the Mercedes-Benz range.

Front and rear axle are designed for tough off-road stresses with both being attached to a subframe and therefore doubly isolated from the vehicle body. The mounts of the steering arms and axle beams are larger than in the previous generation. In concert with the more rigid force transmission points for the wheel reacting forces, this enhances smoothness and ride comfort.

The front wheel suspension is a double wishbone suspension with the upper wishbone in a high position, which benefits spring travel when driving off-road. All transverse control arms and the steering knuckles are weight-optimised forged aluminium components whose light weight and rigidity provide ideal conditions for low rolling noises. The new design of the front axle ensures separate introduction of longitudinal and lateral forces, which benefits both the vehicle dynamics and suspension comfort.

The four-link rear suspension adopts the concept of the preceding version, but has been further advanced with respect to weight, handling dynamics and vibration comfort. Its control arms are also mostly of aluminium: wheel control is by a cast aluminium lower wishbone and a forged aluminium upper strut rod, as well as an upper camber strut of sheet steel. 

Comfort at a controlled level AIRMATIC with adaptive damping

The standard-fit AIRMATIC air suspension responds particularly sensitively. It combines air suspension bellows with adaptive ADS+ dampers whose characteristics can be fully automatically varied at each individual wheel, in both the compression and rebound stages. While driving, a sophisticated sensor system and algorithms set the dampers according to the quality of the road to ensure that, for example, driving over a bump with just one wheel is not transmitted to the entire axle and the interior. At the front axle the springs and dampers are housed in one suspension strut, but they are separate at the rear axle.

The driver personally and the selected drive modes can change the ground clearance and set-up of the suspension. However, the AIRMATIC control unit also uses sophisticated sensors and algorithms to analyse the driving situation and make automatic adjustments.

The adjustable ground clearance is used for the following functions:

  • On the motorway, the vehicle is lowered by 15 mm to reduce the frontal area and body roll;
  • When the driver selects the SPORT drive mode, the ground clearance is also reduced by 15 mm;
  • Automatic lowering by 25 mm when one of the doors is opened facilitates getting in and out;
  • A switch in the right side wall of the boot allows lowering the loading sill by about 50 mm to make loading easier (deactivated when a trailer is hooked up)
  • In terrain, the standard specification of AIRMATIC allows raising the vehicle by 60 mm. When the ON&OFFROAD PACKAGE is ordered, the vehicle can be raised by 30, 60 and even 90 mm. Automatic ground clearance control in terrain accounts for additional parameters such as the slope of the terrain and the vehicle articulation.

To be able to make the adjustments in the ground clearance quickly, the air suspension system of the AIRMATIC was fitted for the first time at Mercedes-Benz with a closed air circuit, which also runs more quiet. The pump is driven by a 400 W electric motor.

When the driver selects the ground clearance when stationary or on the move, a control lamp flashes until the chosen level has been reached. If a raised ground clearance is not cancelled by the driver when the vehicle is on the road, the suspension control system lowers the suspension depending on speed to ensure safe driving characteristics at all times.

The functions of AIRMATIC can be expanded even further with the innovative E-ACTIVE BODY CONTROL suspension (see next chapter).

Braking system: even larger sized

In line with the further advancement of the suspension, the vented disc brakes all around are now larger and measure up to 400 mm in diameter. Larger brake pads all-round ensure better deceleration with reduced wear. The two-piston floating callipers of the front brakes are of larger and more rigid design. This results in short stopping distances, high directional stability during braking and a longer service life of the wear parts.

With the Engineering Package in conjunction with E-ACTIVE BODY CONTROL, an even more powerful braking system with disc brakes and six-piston fixed callipers is available in combination with specific 21-inch and larger wheel/tyre combinations.

The parking brake of the new GLS is electrically operated and uses a combination brake calliper. Pressing and holding its switch to the left under the rotary light switch on the dashboard at speeds above 4 km/h initiates an emergency stop. It is not performed by the parking brake, but by the service brake and is accompanied by the activation of the brake lights.