Next BMW 5 Series will have all-steel chassis

Rumors | March 11th, 2009 by 18

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 …

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.

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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 ]

18 responses to “Next BMW 5 Series will have all-steel chassis”

  1. I guess not having the best safety ratings has been an issue for them. If they don’t gain any weight and has more strength and rigidity then its the better solution

  2. Tom says:

    wtf this sucks i’m buying mercedes now if they’re going down this path.

  3. @Tom: LOL what are you complaining about . They won’t gain weight, and it safer and more ridged I don’t see where the problem is ?

  4. Gord says:

    I’m pretty sure the new 7 is heavier than the old, so maybe the new 5 series will also be heavier.

  5. Giom says:

    That steel frame construction sounds just as complicated. I wonder how much easyer it is to procuce than the alluminum.

    Another question this raised for me was concerning the Audi aluminum chassis. Is that an aluminum only chassis? Is that why they still stick to it?

    Horatiu, maybe someone over at germancarzone can through together a technical summery of the tech of chassis. That would be very interesting.

  6. Gord says:


    I could be wrong but I believe VW (Audi’s owner) have invested heavily in developping aluminium for car usage. The A8 is all aluminium chassis or spaceframe I believe.

  7. Doug says:

    I’d be very curious to know why aluminum is more expensive to fabricate, aside from the welding issue. Is that a big deal?

    There has been some experimentation with embedding carbon fiber in steel in the last decade. It’s possible they’ve made this work; could add tensile strength in strategic places while keeping the robustness of steel and the same manufacturing process. I’ve only heard of castings working this way, because the liquid metal can get through the fibers, but not stampings.

  8. Gragop says:

    @Gord: They have, they’re big proponents of using aluminum for production.

    I say boooo steel! means heavier BMW’s.

  9. @Gord: Its heavier because its bigger I think, and has more tech in it, the new 7er is bigger than the older one I’ve seen them side by side

  10. Jordan says:

    @Mohammed AlMomen:

    I agree. I think the extra weight is more the car being bigger and the extra tech. dunno what the difference in engine weight is tho. I read a review and this is no slow car. rated at 5.1sec 0-60 i think. faster than the 335i.

  11. Nizer says:

    It’s great that they’re going to lighter materials for other parts – maybe even getting rid of the cheap plastic that lines so much of the interior – but the bottom line is that lighter is better. The way I see it BMW is missing an opportunity to reduce overall weight and that’s bad. The mid-cycle update of the 5-Series added over 200lbs and I’m still trying to figure out what extra “content” we got in the deal. As for safety and workability, if Audi can make it work…

    IMHO, this tilts the bar that little bit more in Audi’s favor.

  12. Giom says:

    @Nizer: If I’m understanding this correctly, I’d say that BMWs issue is a mixed medium. One chassis, but alluminum up front, and steel for the rest. The issue is mating the two materials.

    Now, Audi’s set-up is all alluminum -and that only for the low volume (relatively) A8. I believe the RR Phantom also use a full alluminum chassis.

    As long as they’re using a new state-of-the-art steel composite, I’m happy. They didn’t ‘just go back to steel’.

  13. Jordan says:


    totally agree with you. from what i read it’s not just an all steel chassis. like you said it’s a new state-of-the-art steel COMPOSITE…. i think composite being the key word.

  14. I remember from the factory tour a couple years back , the tour guide told us that BMW mates the front aluminum with the rest using some kind of glue

  15. Nizer says:

    @Giom: I read the new steel composite notes as well. My point was that if they went all aluminum like Audi they could reduce weight, not just attempt to keep weight the same. Colin Chapman’s genius was understanding that when it comes to vehicle dynamics, weight trumps all.

  16. I’m sure the insurance industry had some input behind the decision to go back to an all-steel chassis. BMW initially refused to certify independent body shops to repair the E60 (and E90). There are tales of cars sitting in body shops for months waiting for repairs. IIRC, the repair process involves using adhesives similar to the ones used in the aerospace industry. Also, if you perform welding repairs on aluminum, the entire structure would need to be heat treated again.

  17. Nizer says:

    Here’s a quick comparison to make the point a little clearer. The Audi A8 weighs 4400lb. The new 750i weighs 4564lb. But to make it fair you need to add the weight of 4WD system. Using the 535i vs 535xi, the 4WD adds 250lb. So a comparable 750i with 4WD, if BMW made one, would weigh on the order of 4800lb vs the A8’s 4400lb. That 10% weight saving translates into a faster, more efficient, and better handling vehicle, all else equal. And Audi sells the all aluminum-framed A8 with a $74k base price verses $80k for the 750i.

    Don’t get me wrong, I drive a 535i and am a BMW fan. i just think they need to get back to focusing on building light-weight sport sedans like the 3.0 CS, 2002tii, etc., and get away from building over-contented land yachts.

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