If it ain't broke, don't fix it.

If it ain't broke, don't fix it.

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

This specific journal entry covers my unboxing impressions of the SMG3 prototype.

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

If it ain't broke, don't fix it. 

YFCM has made 600+ M3 V8 V2 carbon driveshafts since its introduction in 2016. The replacement rate has thus far been below 3% and exclusively for vibration related issues. Most importantly, there has been 0 case of ungluing at the flanges. 

I've since had YFCM develop the E46 M3 applications. It required a rework of the transmission and CV flanges specific to the E46 chassis - it was a lot of work. 

CTRL+C & CTRL+V from the E9x M3. 

The E9x M3 and E6x M5 not only share the same engine architecture, the driveshafts were essentially one of the same. The tube lengths varied on the chassis (5 series v 6 series) and transmission type (SMG3 v 6spd). 

The transmission flange was however shared across all applications. This allowed the rapid development of a working prototype for me to review. 

M. Lee got an E60 M5 on the lift to validate the specifications in June. 

M. Lee used his off-the-shelf, patented E9x M3 transmission flange and sourced the correct E60 CV flange, and got to work winding the tube.

I received the working prototype in mid July. 

That was fast. 

Unboxing the E60 M5 SMG3 prototype.

This was a familiar feeling - yet it always is a treat. This is truly engineering porn. 

The winded carbon tube. 

The most obvious qualities to the driveshaft is its carbon tube. This is carbon like you rarely see. It is winded from pre-preg & autoclave'd carbon filament sourced from Toray Industries in Japan. 

The various carbon layers are topped off with the signature filament braids. 

The patented flange. 

The flange is machined from 7075 forged aluminum. This grade has roughly 2x the tensile strength and 1.5x the shear strength of commonly used 6061 forged aluminum. 

The self-locking mechanism of the flange is something better understood upon unboxing. The flange is machined following a design file that has the carbon tube fitting within the flange itself - that effectively locks them together. 

The carbon tube and flange joint is then sealed for a weather-proof use. 

The transmission flange is also fitted with the OE style rubber guide. 

The CV. 

The CV flange is a commercially sourced unit specific to the E60 M5 and M6 chassis. 

It is oiled and telescopic. The CV, the carbon tube strength and the guibo allows the driveshaft to endure the SMG3 hits over the long run. 

The cap can be loose upon receiving it. It is held on firmly as you bolt it to the differential during installation. 

The CV also has notches to pry off when removing it for maintenance in and around that area. The CV flange is also sealed off to ensure a weather-proof use. 


Up next: it gets fitted to my V10 M5 SMG3 and beaten hard for months and thousands of kilometres. 

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