Lots of ink has been spilled on carbon driveshafts and it needs to be debunked.
"The tubes are weaker than steel!"
A common myth is they are weaker than steel driveshafts.
The reality is carbon tubes achieve much higher torsional rigidity specifications: they are up to 3x stronger than steel.
I highly recommend to watch the following video by Richard Hammond comparing material properties of carbon vs steel driveshafts at the Lotus factory.
Many believe BMW M dropped the carbon driveshaft in the F8X M3/M4 due to carbon tube weakness.
That is wrong.
"They unglue at the flange!"
This isn't totally wrong: it is technical challenge many brands failed at.
BMW M suffered from ungluing transmission flanges. They issued an official recall on the F8X M3 & M4.
MFactory notoriously failed when attempting to retro-engineer the authentic, patented product you're about to read on today.
Due to their poor transmission flange design, they had to use a larger diameter carbon tubes to match the outside diameter of the transmission flange.
Below is the counterfeit MFactory V3 using a transmission flange riveted to the tube.
In short: vibrations are the results of poor engineering and quality control.
The ungluing transmission flange problem led many brands making carbon driveshafts to use a double CV joints or U joints.
These designs eliminate the flexdisc (guibo) that is specifically designed to reduce drivetrain vibrations and clunk noises.
The picture below shows the YFCM E46 M3 driveshaft that retains use of the OEM guibo.
Below is the CV flange on the YFCM driveshaft to bolt up to the differential.
The results are much heavier driveshafts, added vibrations and a product with a very narrow range of use.
The added weight, larger diameter tubes and riveted flanges make balancing the carbon tube of these inferior products extremely difficult.
As such, they use balancing weights across the tube.
Below is the MFactory counterfeit V3 driveshaft on the right that I personally tested on my E92 DCT M3. It had 3x weights across the tube.
"Even BMW M dropped it!"
BMW M dropped the carbon driveshaft as they needed space in the transmission tunnel to fit emissions related equipment. The carbon tubes have larger diameters.
"BMW will begin adding a particulate filter to the exhaust system at some point in the future to stay compliant with stiffening emissions regulations.
Carbon fiber driveshafts have a larger diameter and therefore take up too much space under the car. The "M-specific high-performance" steel driveshaft being used in its place is narrower enough to work."
- Source: Autoblog.
How YFCM researched and patented a unique transmission flange design, developed a proprietary carbon tube manufacturing method and engineered their own proprietary balancing equipment.