New BMW M3 and M4s will be fitted with steel driveshafts instead of carbon fiber ones as a result of the German manufacturer complying with emissions regulations, according to Autoblog.
Apparently, the old carbon shafts were too thick to accommodate a new particulate filter on the exhaust system. A narrower, "M-specific high-performance" steel part will take their place instead. BMW asserts that it has engineered the steel shaft to retain the "superlative performance and handling qualities" achieved with the carbon fiber component. How true that is remains to be seen. Not only would a steel driveshaft result in a beefier curb weight, but it would also mean more direct weight for the engine to move, making it less rev-happy than before, however slightly.
We guess those who absolutely demand a woven shaft in their luxury sports sedans will just have to drive an Alfa from now on.