The buildup to Interbike has been both long and hectic for us, but we are totally thrilled with the result of our first project, the Titus Project-29.  This is not only the next step of the mountain Di2 project we started almost 2 years ago, but has countless applications for the road group as well.  A programmable Di2 brain that in this setup uses a single shifter with multiple modes including both sequential shifting of front and rear derailleurs together as well as the ability to manually shift either derailleur independently.

The – new – Di2 Brain

The central part of the project is this little “brain” that makes virtually anything possible.   This was designed and built for us by forum member jeffr (Jeff Roberson.)  Jeff’s resume is really very impressive and we are completely honored that he undertook this project fabricating everything we wanted and then so much more.  We can’t express our gratitude to him enough.  This little board, a proof of concept, that he built not only takes Di2 to the next level, but kicks open countless doors for the future.

Component and Build Description

We started with a custom Titanium hardtail frame from Titus.  Then we added a modified Cannondale Carbon Lefty fork.  For the wheels we used the sub 950 gram tubular set that we showed earlier this year(Edge tubulars, Tune Cannonball/Dezibel and Pillar spokes)  Dugast tires were added to the wheels to finish them off.  For the brakes we went with Kcnc’s new X7 disc brake system but added in some Scrub Race Day rotors to cut the weight even further. We used a whole host of other Kcnc parts such as the Morion ceramic headset and their hollow headset spacers. We also used the new double chainring K2 type cranks from Kcnc. Other Kcnc products on the bike were the bar end plugs, skewers, valve extenders, grips, seat collar, Ti DLC Knife pedals and Ti pro lite seatpost as well as a mix of Kcnc tuning parts to color and lighten the rear derailleur. A custom Edge (now known as Enve) stem had to be made to house the brain, and a pair of Edge/Enve sweep bars were mated to that. The bike was finished off with a Tune Kom Vor saddle and Tune’s new bottle cage.

The finished bike weight tipped the scales right at 16 pounds.

At first glance the bike appears to be pretty straight forward, much like last years Di2 mountain bike.  Notably absent however is the battery, which this year was placed inside the seat tube.   The most important missing piece though happens to be the left shifter.  In it’s current mode the shifting is done via the single right shifter.  Although potentially limitless we’ll describe two shifting setting currently programmed into the brain.

Complete Bike Build

Automatic Mode

Two buttons, one for an up shift and one for a down shift.  The brain basically uses calculated gear inches to decide on the proper next gear.  It’s not as simple as a linear list though.  The bike does not just run back and forth through pre-set options.  It is configured to remove duplicate gears as well as cross chaining.  But more importantly it reduces the amount of front chainring shifts it makes.  If you are in your small ring and reach a point where it needs to shift the front to get a higher gear it does that.  But then if you shift back to a smaller gear it does not return the chain to the small ring with the next down shift.  It knows there are other options to get that same gear by staying in the larger ring and as long as one of those options does not create a bad chainline it will go for one of those.  That means in moving from the lowest gear on the bike to the highest it only needs to shift the front derailleur once.

Manual Shift Mode

There are also other modes available such as a manual shift mode.  In a manual mode the right shifter buttons independently move the rear derailleur up and down as they would in a normal Di2 setup.  To shift the front derailleur both buttons are pushed at the same time.  Since the bike is a double up front there is no need to tell it what direction to shift in manual mode, but only to shift to where it currently does not reside.

Other Shift Features

One other nice feature that Jeff built into this brain is the ability to dump gears.  As a further improvement gears can be dumped as many as 13 at a time and in either the up or down direction.  He opted to slow this dumping from it’s full potential speed in to reduce the chance of dropping a chain.  However, even in this slowed down mode it can go from the highest gear on the bike, a 42/11, to the lowest gear on the bike, a 29/32, in just over 1 second and without having to soft pedal.

There are also other modes which will eventually be mentioned.  Jeff, when asked, simply replied, “if you can think of it, it can probably do it.”