The fix is in.

The fix is in.

"These build journal entries are part of a Special Series on the development of the E60 M5 & M6 Carbon Fiber Driveshaft by YFCM Composites.


I doubled down on the SMG3 using modern carbon technology used in the F8x M3. The SMG3 is damned no more.


In this entry, I record a video clip and document my driving impressions in a caricature that only SMG owners will resonate with: the anticipation flexes.


These entries are written in collaboration with M Lee: lead engineer and patent holder to YFCM's innovations."
- Matt

The anticipation flexes

The stock SMG3 driving experience is best described with the anticipation flexes that all owners instinctively do, in various sauces, depending on the RPM and SMG's hydraulic pressure. 

The high rpm flex. 

I most often characterize this when I assume I'm in 6th gear about to slam in 7th.

I catch myself pushing my body against the seat expecting the whipping action of the SMG3. 

I was actually in 7th gear. 

The low rpm and reverse flex. 

The low RPM behaviour of a stock SMG3 is downright atrocious. It will hesitate or  slam in gears, rattle the flywheel and upset the entire drivetrain, rocking it forward and backward on its mounts. 

The any range shift flexes. 

No matter what range you are, what throttle pressure you apply and what Drivelogic setting you're in, you're flexing and bracing yourself. 

No more flex. 

The carbon fiber driveshaft has critical benefits: 

  1. It's stronger: carbon tubes have higher torsional rigidity than steel. 
  2. It's lighter: carbon is lighter than steel. 
  3. It absorbs more shock: the tubes are wider and hollow.
  4. It's 1 piece instead of 2: it deletes the center bearing.
  5. It's vibration free: it retains the flexdisc (guibo). 

All while being backed by a 1 year replacement warranty. 

The engineering prowess is in the self-locking flange, and its design allowing use of the original flexdisc. 

The magical element: stiffness. 

The 1 piece carbon driveshaft core technical improvement over the 2 piece steel driveshaft is stiffness. 

The tube's stiffness is entirely derived from the unique pre-preg, winded carbon fiber construction by YFCM. 

Stiffness has one overarching benefit: the drivetrain is tighter

The carbon driveshaft is winded, cut, glued, riveted and its flanged machined to precise tolerances. 

Tighter is smoother.

It's better in the daily zones. 

The carbon driveshaft solves arguably the biggest SMG drawbacks: the daily driving experience.

I've recorded a low speed, low RPM, low temperature video. These are the worst possible conditions for the SMG3. 

Tighter is faster. 

Improved throttle response. 

The tighter drivetrain tolerances improve throttle response by reducing slack. 

I previously recorded a video clip with the intention to showcase the mid and top end sound of the S85 CSL carbon plenum. It also featured the flywheel and carbon driveshaft behaviours at Wide Open Throttle (WOT). 

The high engine speed kickdowns and S6 WOT shifts across the mid and top end are nearly DCT fast.

Tighter is maddest.

At 310kph, it didn't vibrate. 

That's all I'm going to say about that. 

The S6 WOT madness is channeled. 

Ever since I first experienced full throttle S6 shifts at redline, I had developed the habit of lifting just ever slightly to smoothen out shifts. 

Doing this with the carbon driveshaft now has the opposite effect. The clucth operation is executed faster, and lifting creates a jerk. 

Keep it floored. 

As you keep it floored through S6 shifts, it feels nearly like the signature torque transfer through WOT gear changes experienced in DCT gear shifts. 

The shift interruptions are visually represented by the slight speed loss in the middle of the blue line. 


The V10 SMG3 application has been the most impactful use of the carbon driveshaft technology. 

There are no drawbacks. 

It's purely a positive. 

The YFCM carbon driveshaft should be your first mod if you care about the driving experience. 

It makes the SMG3 truly great again. 

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