"These build journal entries are part of a special series on the development of the S85 SMG3 carbon forged steel lightweight flywheel by TTV Racing. 

This specific journal entry covers my unboxing impressions of the flywheel and a dive into its technical specs."

- Matt

The M5 V10 life forces you into positivism [...]

In August, my V10 M5 broke down as I begun testing of the prototype carbon fiber driveshaft.

The radiator's electrical fan failed and the S85 would quickly overheat in stop and go traffic. Shout out to Michael @ Luciano Auto Wreckers out in the Bronx for sourcing a used unit: I still owe you for this!

[...] and finding irrational ways to make up for time at the shop. 

I ended up doing just that: I got with TTV Racing who developed the S65 DCT lightweight flywheel and got to task developing the SMG3 S85 Lightweight flywheel.

The lowdown. 

TTV Racing already had the specs to make this. I quickly received the flywheel via DHL express later in September and unboxed it to cover its technical features. 

It's machined from carbon forged steel. 

The flywheel is made from carbon forged steel. It's a higher density material than commonly used aluminum.

Carbon forged steel is also materially stronger. It matters most to us V10 owners due to its increased resistance to deformation from heat & torque. 

Carbon steel offers a wider range of machining optimization possibilities: you can occupy the same space with less weight, or more space with similar weight. 

This leads us to the next point. 

It works with OE clutch & software. 

Most companies have you spend to get their package of clutch & aluminum flywheel.

TTV Racing designed the flywheel to fit with the OEM clutch. That plays a big part in how street friendly these end up being. 

The surfacing of the flywheel is machined to match the OE clutch. 

Upgrading your clutch is also quite pointless on the S85 V10. It comes standard with a dual disc design: it's extremely tolerant to power. 

The OE clutch is made by Sachs. It has never felt weak contrary to what some aftermarket clutch manufacturers say in the brochure. More info in the upcoming installation journal entry.

The flywheel is machined to fit with the OE starter. The alignment is guided by a slightly larger bolt hole. More information will be found in the journal entry covering the installation. 

These dowel pins are machined to fit into the OE clutch. 

 

It will require new aftermarket bolts. 

In preparation for your install, you will need to source new bolts as the OEs are encased into the OEM flywheel and cannot be retrieved easily. 

The TTV flywheel is designed to fit with Grade 12.9 bolts in M12x1.5x35mm dimensions. I used the ARP bolt kit #: 764-1003.

It's high speed balanced. 

TTV has 2x high speed balancing machines in house designed to achieve OE matching balancing to match with the inductive sensors of the S85. This is critical as it has a direct impact on the camshaft positions.

The balancing is done by machining speed holes on the flywheel: taking away weight at areas specified by the balancing machines. 

The 3rd balancing hole was punched through. This was deemed inconsequential by Ben at TTV after balancing validation. More on this in the installation journal entry. 

  

Up next: time to install this and give you a few tips.