Axles And Suspension - SN32.00-P-0001-01G
Model 118.3
Front axle
Similar to the preceding series, the new CLA-Class has a MacPherson front suspension.
At the front axle module of the new CLA-Class, a hub unit is in each case bolted onto the cast-aluminum steering knuckle. The wheel control takes over in each case one transverse control arm below the wheel center, one suspension strut and one tie rod. The transverse control arm has been designed as a forged aluminum part in the new CLA-Class. As a result, the weight is reduced and the unsprung masses are kept low.
From a driving dynamic perspective, the further developed front axle offers high vehicle responsiveness, high ride comfort and high driving safety due to a corresponding design and layout of the elastomer bearings.
During the determination of the axle geometry, particular importance was placed on keeping the steering pull during acceleration as low as possible. The rack-and-pinion steering has been moved behind the wheel center when viewed in the direction of travel due to the front-end assembly and the new engines for the CLA-Class.
Rear axle
A 4-link rear axle will be installed in the new CLA-Class.
4-link rear axle
In the 4-link rear axle, three control arms and one trailing arm per rear wheel absorb the forces and torques that occur. The longitudinal and lateral dynamics of the vehicle can thus be adapted in a targeted manner and almost independently of each other. The maximum driving stability and ride comfort is thus achieved. The wheel carriers and spring links are made from aluminum to adjust the driving characteristics in the direction of responsiveness and ride comfort.
The used aluminum share for the suspension components is one of the highest of all known suspension systems for this vehicle category. Low unsprung masses allow for a particularly precise sensing of the road surface and thus a high ride comfort.
To reduce the audible and tangible vibrations, the new CLA-Class will have a rear axle carrier that is decoupled from the bodyshell by elastomer bearings.
Suspension and damping
The suspension of the new CLA-Class contains McPherson spring struts with twin-tube shock absorbers at the front axle and single-tube shock absorbers with separately installed springs on the rear axle. Stabilizer bars are also installed on the front axle and 4-link rear suspension.
The following suspension variants are available:
- Comfort suspension with steel springs (standard equipment)
- Comfort suspension with steel springs and lowering (market-specific, with code 677 (AGILITY CONTROL suspension))
- Suspension with adaptive damping adjustment (with code 459 (steel suspension with damping adjustment))
Comfort suspension with steel springs (standard equipment)
A conventional damping system is part of the standard suspension. The setup of the twin-tube shock absorbers was selected so that the tractive/compressive forces at the front axle are in proportion to each other so that the dynamic wheel load fluctuations are reduced. Both the vehicle dynamics and the driving safety are further improved as a result. Sufficiently large spring travels, friction-optimized dampers with corresponding support length and precise transverse force compensation are the requirement here for comfortable suspension characteristics.
Comfort suspension with steel springs and lowering (market-specific, with code 677 (AGILITY CONTROL suspension))
Harder front and rear axle springs and adapted shock absorbers at the front and rear axles are part of the comfort suspension with lowering. The vehicle level has been lowered at the front and rear axles by approx. 15 mm in comparison to the standard suspension.
Suspension with adaptive damping adjustment (with code 459 (steel suspension with damping adjustment))
The new CLA-Class optionally has active adjustable damping. In combination with the drive program selected by the DYNAMIC SELECT, you can thus select between a comfortable or sporty shock-absorber behavior. Depending on the selected program, the shock-absorber behavior is adapted to the road conditions and the driving style of the driver. The driver is no longer tied down to a single damper design, rather can enjoy an optimized comprise between comfort and sportiness. To reduce the pitching and rolling of the body and improve the wheel loads and tire adhesion, the damping becomes harder during acceleration, braking procedures or steering maneuvers.
With the active damping control, the requirements are created for highlighting the vehicle dynamics without having to compromise on the driving safety or ride comfort.
DYNAMIC SELECT
DYNAMIC SELECT with its drive programs is a package that integrates systems and functions (steering, drivetrain and optionally suspension, ESP®). A special driving style is offered to the driver. The driver can choose a particularly comfortable driving mode, a sporty one or one that guarantees optimum fuel consumption. Depending on the equipment installed, the driver can select between different preconfigured drive programs and a drive program that the driver can largely configure themselves.
Transmission modes
- Individual
Depending on the vehicle equipment, the settings for, e.g. the steering, drive, ESP®, and suspension, can be changed in the "Individual" drive program.
- Sport
The Sport drive program supports a sporty driving style with a good level of comfort.
- Comfort
The Comfort drive program is a well-balanced drive program with corresponding suspension tuning and fuel consumption-optimized drivetrain tuning. The "Comfort" drive program is automatically set when the ignition is restarted.
- ECO
In the ECO drive program, the vehicle is designed for minimal fuel consumption.
Steering
In the new CLA-Class, an electromechanical rack and pinion steering gear is used that is located behind the wheel center. The standard speed dependent support of the steering force is generated by an electric motor. The support of the steering force is transferred via a reduction transmission to the rack and pinion steering gear. The integration of the electric motor and control unit allows for a compact design.
Please find further information in the function description GF46.35-P-9900A "Steering basic function".
Brake system
In the new CLA-Class, a hydraulic dual-circuit brake system in the so-called X-configuration is used with the standard brake control function ADAPTIVE BRAKE. This brake system offers the standard high quality in Mercedes-Benz vehicles with regard to:
- Braking distance
- Response time
- Creep strength
- Service life of brake linings
- Directional stability when braking
In this connection, the vehicle-specific conditions such as the axle load distribution, weight and performance are taken into consideration.
Electric parking brake
The electric parking brake is a component of the standard equipment and acts on the rear wheels. The braking parts are held, de-energized, in the braking position by a self-locking mechanical effect. The electric parking brake is operated with the control element of the parking brake in the instrument panel next to the exterior lights switch.
New in the CLA-Class is the automatic parking brake in vehicles with manual transmission. If the vehicle comes to a standstill, the ignition is switched off, or the driver's door is opened, the electric parking brake is automatically applied. If the parking brake is not applied and the driver's door is opened, a red warning message "Risk of vehicle rolling - electronic parking brake not applied" appears in the instrument cluster.
Tire pressure monitor
New in the CLA-Class, except in combination with the engine M139, is the tire temperature monitoring function. The tire temperature is monitored with the same sensors as the tire pressure. In the case of a significantly increased tire temperature due to overloading, the warning message "Tires overheated" appears in the instrument cluster. In the message, the tire temperatures are shown and the affected tires are highlighted in color. If the driver continues at the same high speed in spite of the previously mentioned warning, the warning message "Tires overheated, reduce speed" appears.
Since this does not concern a legally required warning, the cruise control warning lamp is not switched on for the temperature warning.
Please find further information in the function description GF40.15-P-9900A "Tire pressure loss detection system basic function".