Mercedes Benz A Class – Chassis, suspension and braking system







Published by Gerald Ferreira Date: August 29, 2013
Categories: Mercedes-Benz, Mercedes-Benz A-Class

Performance, precision and agility

  • AMG sports suspension with newly developed front and rear axle
  • AMG performance suspension available as an option
  • Electromechanical dual-pinion AMG speed-sensitive sports steering
  • AMG high-performance braking system for spontaneous deceleration
  • Mercedes-Benz A-Class

Mercedes-Benz A-Class Chassis

High agility and dynamic handling coupled with hallmark Mercedes comfort are major strengths of the A 45 AMG. This AMG high-performance car features state-of-the-art axle technology. The McPherson front axle and four-link rear suspension are all-new developments from Mercedes-AMG. During design and development, the focus was firmly on ensuring maximum performance and the best possible traction when driving extremely dynamically. New, stiffer steering knuckles are used on the front axle. As well as ensuring direct steering behaviour, they also see to it that the camber remains constant when cornering at speed. Experts refer to this as "camber stiffness". The rear axle features all-new strut bearings, while the subframe is rigidly connected to the body. All of the understeer/oversteer characteristics have been optimised along with the rear axle spring travel. Hallmark AMG features include the front and rear axle with more negative camber as well as optimised, stiffer elastokinematics for much higher lateral dynamics.

The AMG sports suspension is equipped with specifically tuned spring/damper units, new head bearings and larger stabilisers, meaning that the driver benefits from a more direct driving feel and a reduced rolling tendency in fast double bends. Alternatively, the A 45 AMG can be equipped with the optional AMG Performance suspension. Stiffer spring/damper units all round result in even better road feel as well as reduced body pitch and roll.

AMG speed-sensitive sports steering for highly precise steering

The electromechanical dual-pinion AMG speed-sensitive sports steering ensures agile cornering and exceptional feedback at the critical limits. The basis for this is the AMG-specific, speed-dependent power assistance and a constant steering ratio (14.5 : 1). The electric motor is located on the steering gear to save space. Sporty response from centre position, optimum road feel and highly precise steering, especially when adopting a sporty driving style, are among the key attributes of the AMG speed-sensitive sports steering. The high-performance control unit processes the parameters captured by the ESP® control unit – including vehicle speed, steering angle, steering angle speed, lateral acceleration and also understeer/oversteer characteristics – and in a split second calculates the forces which the driver needs to input into the steering in different driving situations – from parking to high-speed motorway driving. Active damping enhances the feeling of safety when driving straight ahead at high speed.

The electromechanical dual-pinion AMG speed-sensitive sports steering additionally enables various steering assistance functions which are activated by the ESP® control unit. These include:

  • Countersteering in case of oversteer
  • Corrective steering when braking on road surfaces offering
    different levels of grip (split-friction braking)
  • Compensating crosswind and road gradients
  • Use of Active Parking Assist (optional extra)

A Class

AMG high-performance braking system with a wealth of convenience functions

The A 45 AMG owes much of their excellent dynamic handling to the AMG high-performance braking system. One of its major attributes is the spontaneous and reliable braking effect. Vented, cross-drilled and grooved disc brakes are fitted on the front and rear axle. The front axle features 4-piston aluminium fixed callipers, while the rear axle has single-piston combination callipers.

Brake data at a glance:

AMG high-performance braking system
Front   axle:
Brake   calliperBrake   disc

 

Diameter
Thickness

Weight*

4-piston aluminium fixed calliperIntegral technology, vented,   cross-drilled, grooved

350 mm
32 mm
12.2 kg

Rear   axle:
Brake   calliperBrake   disc

 

Diameter
Thickness

Weight*

Single-piston combination calliperIntegral technology, vented,   cross-drilled, grooved

330 mm
22 mm
7.2 kg

*Weight of the brake disc

One particularly convenient feature is the HOLD function as also seen in 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.

The electric parking brake is standard and features servomotors that act on the rear axle's combination callipers. The parking brake is operated using a button on the instrument panel to the left of the steering wheel below the light switch, freeing up space on the centre console where the handbrake lever would normally be. A useful convenience function makes hill starts easier: if the driver is wearing the seat belt and accelerates enough to drive away, the parking brake is released automatically. 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.

Two wheel/tyre combinations to choose from

Contact with the road is provided by wide-base 235/40 R 18 tyres – fitted on AMG 8 x 18 alloy wheels as standard. The two versions available as optional extras are one size larger: the AMG 8 x 19 alloy wheels with 235/35 R 19 tyres are available in a choice of two colours, high-sheen titanium grey or matt black with high-sheen rim flange.