BMW 5 Series: Rear axle

Five-link rear axle in the G30

1. Support bearing
2. Shock absorber
3. Rubber mount of the rear axle support on the body
4. Rubber mount of the rear axle support on the rear axle differential
5. Air deflector
6. Camber control arm
7. Wishbone
8. Camber link
9. Wheel bearing unit
10. Wheel carrier
11. Trailing arm
12. Control arm
13. Compression strut
14. Axle support

The five-link rear axle is characterized by precise wheel guidance with outstanding driving dynamics.

This is particularly noticeable with respect to the following characteristics:

• Directional stability, target precision
• Load transfer characteristics
• Self-steering response
• Lane changing stability
• Transient handling characteristics (cornering/straight-ahead driving)

It has been possible to substantially reduce the conflict between the goals of driving dynamics and comfort by implementing the following measures:

• Double-elastic mounting.
• Rubber mounts between rear axle differential, rear axle support and body.
• Preload-reduced rear axle mounts.

  Lower torsion stress on the rear axle bearings thanks to spring struts positioned wide to the outside.

• Large support area for the rear axle support.
• Low unsprung mass thanks to innovative sheet steel wishbone technology in conjunction with aluminium forged wishbones and aluminium-wheel carriers.

The large support for the rear axle support and the preload-reduced axle construction are of great significance for the outstanding driving dynamics on the one hand and for acoustic decoupling on the other hand. This makes it possible to install powerful, high-torque engines and to reduce the introduction of road noise into the vehicle.

It has been possible to produce the various wishbones, with the exception of the upper wishbone, in a sheet steel design. Sheet steel wishbones offer similar weight advantages to aluminium forged wishbones, but are cheaper to produce. They are always used when a simple mounting geometry is used (straight wishbones). The top wishbone has been manufactured as an aluminium forged wishbone because of its more complex design.

Replacement of the rubber mounts on sheet steel wishbones as a service operation is not permitted.

The entire wishbone must be replaced in the event of wear to a rubber mount.

Notes for Service

The following table shows when wheel alignment is necessary on the rear axle when a component is replaced.

The following table shows when wheel alignment is necessary on the rear axle when a component is undone.

Rear axle positioning

Comparison of rear axle on the G12 with the G30

1. Rear axle of the G12
2. Rear axle of the G30

1. Body
2. Mounting for rear axle support
3. Centering mounting for rear axle support
4. Rear axle support
5. Rubber mount of the rear axle support

On the G12, no centering mounting dowels are fitted on the body for alignment of the rear axle. A new special tool was used to align the thrust angle when installing the rear axle support.

The centering mounting dowels are used on the G30. No special tool is required for installing the rear axle support.

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