While dated now, safety features of the 124 chassis are still saving lives

Safety

Body structure

Many structural safety features were developed for the E-Class chassis:

  • Side impact protection consists of two structural crossmembers beneath the front seats, one under the rear seat, and one at the base of the windshield (arrow).

The crossmember below the windshield also serves to prevent intrusion of the engine.

  • In 1973 Mercedes-Benz found that most frontal collisions do not occur straight on, but rather as offset impacts where the cars meet at an angle. Collision data revealed that 40% or less of the frontal area of the vehicle is involved in the impact.
  • A forked load bearing front end structure was developed to divert impact forces and also help prevent intrusion into the passenger compartment. During an offset-frontal impact, a substructure of reinforced steel panels serves to deform the body progressively and redistribute the kinetic energy. Through this structure, the incoming loads are shared by both sides of the body unit rather than concentrated to one side.

Other features contributing to vehicle safety:

  • Fuel tank located above rear axle for rear end impact safety
  • Structural body and chassis reinforcements with ten high tensile-strength crossmembers for superior cabin protection
  • "Safety cell" passenger compartment with front and rear body sections designed to crumple and absorb energy
  • High-strength low-alloy (HSLA) steel panels and formed stiffeners in the underbody and doors for increased rigidity
  • Bumper mounted crossmembers welded to side members for dissipation of offset-frontal impact forces.

 


Supplemental Restraint System (SRS)

At the time of the model’s US debut, the standard Supplemental Restraint System (SRS) included a driver side airbag in the steering wheel and pyrotechnic seat belt tensioners for driver and passenger.

  • A passenger side airbag was available in later years.

The airbags are the "supplemental" restraint component of the system because the seat belts are the primary restraint in a collision. For airbags to work effectively, seat belts must be worn at all times.

  • The driver side airbag is located in the hub of the steering wheel. The airbag is constructed of a cloth bag folded in a particular way, inflated by a solid fuel gas generator integrated in the airbag unit. The ignited fuel burns very rapidly to instantaneously inflate the bag. After deployment, the gas rapidly escapes from four vents in the bag.

Beginning in 1990, a passenger side airbag was available as an option and later installed as standard equipment. The passenger airbag uses two gas generators. The generators are not fired in unison. The first is activated simultaneously with the driver’s bag and the second 15 milliseconds later.

  • The main components of the SRS are:
  • SRS light in instrument cluster
  • SRS impact sensor
  • SRS control module
  • SRS airbag(s)
  • Seat belt tensioners

The SRS light in the instrument cluster illuminates for about two seconds when the vehicle is started. This is a self-check of the SRS circuit. If a problem is found, the indicator light stays on and the SRS system is disabled.

The SRS impact sensor is mounted on the center tunnel of the body, behind the ashtray. The sensor electrically signals the SRS control module when a programmed deceleration threshold is reached. This signal is the basis for activation of the airbag(s). All the electrical contacts of the airbag system are gold plated to eliminate the possibility of corrosion and electrical resistance.

Crash research has shown that static seat belts are inherently loose and seat belts do stretch. Belt slack is also an integral part of the belt retractor design. Crash analysis further revealed that in severe collisions many drivers suffered steering wheel or windshield injuries even when seat belts were worn.

  • The E-Class features an automatic tensioning system that incorporates gas-generating (pyro-technic) technology. The tensioner retracts up to five inches of belt when the airbag is triggered. The combination of airbags and seat belt tensioning has made the cabin of the E-Class car a safe place to be in today’s harried driving environment.

 


Chassis and Suspension

This heading covers the various integrated electronic braking (ABS) and traction-enhancing systems (4MATIC, ASD and ASR) as well as the front and rear suspension information.

  • For more detailed information on braking, traction, and suspension systems, see Chapter 9 .

ABS (antilock braking)

ABS is the German acronym for Antiblockier System or anti-block system. ABS was first available in European Mercedes-Benz passenger cars in 1978. ABS became standard equipment on all Mercedes-Benz cars sold in the United States and Canada in 1986. The system has proven to be trouble-free and highly reliable.

  • ABS components include an electronic control module, a hydraulic control unit, and speed sensors at the wheels.

 

  • When the wheel is rotating, the wheel speed sensors output a voltage proportional to wheel speed. The control module uses this signal to calculate wheel acceleration. If a wheel is about to lock up, the brake fluid pressure at the wheel is modified by the hydraulic control unit based on input commands from the ABS control module.
 

The system either reduces or maintains the brake line pressure during intervention. The ABS system does not have the ability to apply the brakes.

  • The rapid regulation of the brake fluid pressure during ABS intervention is what causes the brake pedal to pulsate and chatter.
  • 4MATIC, ASD, or ASR systems do not conflict with ABS braking.
  • *info from Bentley Publishers.