Autocar UK reports that the next generation 2011 BMW 5 Series will have an all-steel chassis, giving up the aluminum materials used in the current generation.
Apparently, the change is being made due to costs issues and most important, ease of manufacture. The aluminum chassis has been too costly for BMW over the years and it was more difficult to manufacture in large volumes.
The E60 5 Series uses an aluminum frame at the front, but the rear is still made out of steel. The new BMW 7 Series was the first model to drop the aluminum front-end.
As our friend EnI points out, the aluminum chassis offered some weight savings, but the structural rigidity was questionable, especially after a collision, the frame was very difficult and extremely costly to repair.
As far as the new all-steel chassis, some special techniques are used by processing the steel – a multi phase steel (tubes are made of thinner steel layers reinforced with some other composites – making them lighter yet stronger than classic steel tubes).
As a result, the weight is quite reduced compared to a classic steel frame. BMW X5, X6 and 7 Series are also using such steel body frame. Bottom line is that BMW is not overlooking the weight issue here, and the new 5 Series will be just as heavy as the E60 model, but more rigid and providing higher safety.
There will be more aluminum, composite plastics and magnesium parts used in F10 5 Series, which will compensate in the end for the heavier body frame.
The new BMW 5 Series GT is built on the same structure, following the same plan, so this is a clear indication of what the next 5 Series will bring to the table.[Source: Autocar ]