Suspension: The right set-up for every use

Feb 10, 2014
With the new GLA Mercedes-Benz is adding a new member to the successful SUV family. This compact model reinterprets the SUV concept in a new, modern way, because the GLA is less long-legged and imposing than previous SUVs, and therefore fits perfectly into the day-to-day urban lifestyle.  There are three chassis and suspension set-ups to choose from.
The chassis of the CLA features a McPherson front axle and an independent multi-link rear suspension. Three control arms and one trailing arm per wheel manage the incoming forces. This means that longitudinal and lateral dynamics are independent of one another. The wheel carriers and spring control arms are made of aluminium to reduce the unsprung masses. In the versions with 4MATIC, the rear axle carrier is isolated with rubber bushings for the benefit of ride comfort.
In all there are three chassis and suspension set-ups to choose from:
In the standard-fit comfort suspension the setting of the McPherson double-tube shock absorbers has been selected so that the tension and compression forces at the front axle are at a ratio of 3:1. This reduces the dynamic wheel load fluctuations, benefiting the driving dynamics and driving safety of the vehicle. Small rolling and pitching motions and a reduced tendency to understeer at higher levels of lateral acceleration additionally improve vehicle control.
The lowered suspension (in combination with the AMG Line1 or the Dynamic Handling package) combines agility with ride comfort. Compared with the standard suspension the springs and dampers feature firm and sporty tuning and the level of the car is lowered by 15 millimetres. This reduces rolling motions and enhances driving stability.
With the off-road comfort suspension (optional) the body is raised by 30 mm. This results in improved off-road capability owing to higher ground clearance, a higher seat position and more striking off-roader looks. This suspension variant also features a distinctive steering system set-up.
Compared to conventional systems, the electromechanical Direct-Steer system provides better feedback to the driver and makes an important contribution to the vehicle's overall efficiency, as the servo assistance only requires energy when steering actually takes place. It also allows various steering assistance functions that are initiated by the ESP® control unit. These include countersteering when the vehicle oversteers, steering corrections when braking on surfaces with different levels of grip, reducing the effects of front-wheel drive on the steering and compensation of cross-winds and road camber.
As an optional extra, in the Dynamic Handling package a Sports Direct-Steer system with speed-sensitive power assistance and a variable steering ratio is available. The ratio of the Sports Direct-Steer system in straight-ahead position is the same as that of the basic steering system, and becomes around 20 percent more direct between 5 and 90 degrees steering angle. Straight-line stability is thus retained and agility and manoeuvrability are even further enhanced. Comfort during manoeuvring likewise is improved as the full steering angle already is reached with 1.2 turns of the steering wheel.
With all engine variants the GLA features disc brakes all round. The floating callipers on the rear axle as well as the brake booster are made of aluminium. An especially convenient feature is the HOLD function familiar from the larger model series: when stopping, for example at traffic lights, the driver merely has to press the brake pedal slightly more firmly once to keep the brake engaged until moving off again. The brake is released automatically when the driver steps on the accelerator. In versions with manual transmission the Hill-Start Assist function is able automatically to prevent the vehicle from rolling back unintentionally when moving off on an uphill slope.
The GLA is equipped with an electric parking brake, which operates by means of actuator motors acting on the callipers of the rear axle. The parking brake is activated via a button under the light switch on the left of the dashboard, freeing up space on the centre console where the handbrake lever would normally be. If the button is pressed when travelling faster than 4 km/h, the parking brake functions as an emergency brake: all four wheel brakes are activated by the ESP® hydraulic unit.
In conjunction with the 7G-DCT automatic transmission, the parking brake offers a particularly convenient mode of functioning: when the driver accelerates sufficiently after fastening his seat belt, the parking brake is released automatically.
1The AMG Line is also available with comfort suspension and without Sports Direct-Steer system. In addition, the AMG Line can also be had with the off-road comfort suspension.
GLA 4MATIC drive system
13C1133_04
GLA speed-sensitive steering
13C1133_03
GLA front axle
13C55_09.
GLA rear axle
13C55_10.
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