BMW To Replace Carbon Driveshaft In M3, M4 With A Steel One Due To Emission Requirements

BMW announced that from November of this year onward it will start replacing gradually the carbon driveshaft in the M3, the M4 and the M4 Convertible with an M specific high-performance driveshaft made of steel.

This measure deemed necessary from BMW in order to create “the necessary technical basis for meeting statutory emissions requirements”, which translates into making the M3/M4 compatible with a petrol particulate filter (PPF) that will be required to be installed in major markets at a later point in time.

The company says that the newly developed steel driveshaft is designed up to the high standards of the M3/M4 models, leaving their performance and handling qualities unaffected.

This pre-enabling process will happen for production-related reasons and needs to be carried out universally for all versions of the M3/M4, sans the limited M4 CS and M4 GTS special editions.


  • I would need more infos to understand this decision…

    • Mike Sinyaboot

      The needed particulate filter will not fit due to the diameter of the carbon driveshaft. The steel driveshaft will allow the filter to fit.

    • Kash

      BMW needs to fit new or more filters to the exhaust system to meet impending emission standards, the carbon fiber shaft takes up more room than the steel one. The steel one is just small enough to give them just enough room to squeeze in the filters without having to change too much else.

      • Bash

        How do you know that!? That’s great!

        • jez zza
        • Kash

          Probably read it somewhere the other day, but I also know things made from carbon fiber, like driveshafts and other tube like items, tend to be bigger or have larger diameters to create a more rigid structure than their metal counterparts but they also tend to be woven around a foam core to give it shape before being sealed and cooked and hardened and all that good stuff so the foam core needs to be large enough to maintain its shape to maintain the CF piece’s shape.

      • TheBelltower

        Wow. The more you know…

        • Kash

          pros and cons of CF parts i guess.

      • pcurve

        you’re right. just did video search of Steel Shaft Vs Carbon Fiber Shaft and latter is very thick. (though it was over 3 times stronger)

      • chuck2

        Yep, sad what they have to do bc of ‘packaging’ now.

  • john1168

    I want to know why a steel drive shaft is better for emmissions over a lighter carbon fiber one. I think the engine can rev faster with the carbon fiber one but is there more torque with the steel one??? I have no idea…

    • Kash

      Has nothing to do with weight or power or revving and everything to do with size and needed space. The CF shaft has a larger diameter than the steel one. the steel one leaves more room for more filters to help improve emissions even with the added weight of the steel shaft the cars will still have better emission scores than they did with the CF shaft.

      p.s. The car can rev faster with the CF shaft than the steel one.

      • john1168

        Thanks for the info. That makes sense.

      • TheHake

        So M4 drivers are getting shafted?

        • Kash

          pretty much yeah. lol.

  • Dennis James

    Well, Giulia Quadrifoglio will still have the carbon fiber driveshaft 🙂