Fitting Shimano Di2 Electronic Ultegra gears to a Lynskey Titanium frame

 At the opposite extreme to a 1978 Raleigh shopper, is this swanky thang from Tennessee:

It's a Lynskey R300 road bike, to which I'm going to fit Shimano Di2 Ultegra (6870, so an older version of the groupset, but it's still totally brilliant!). Now, the challenge is that at each bulkhead in the frame, the passage holes are smaller than the tubing. That means, there's a lip around each junction, which makes it awkward to thread anything through. The photo below of the bottom bracket may show this better than my explanation:

There are 6mm exit holes, but these are ok to work with, and standard for Shimano grommets. Here's the one in the head tube (and yes, Lynskey did confirm that the electronic wire (connecting Junction boxes A to B) is intended to go in from this hole around the steerer and into the down tube:

And here's the hole on the chainstay, which I will be wiring up first:

My "threading" wire of choice is an old gear cable, also shown in the photo above. I like using this, as it can be taped easily to the electronic wire plug and still fit in the 6mm hole and pass round tight corners. I'll show you how later. But, the first step is to get this gear cable into the chainstay, with the nipple at the cassette end.  After thinking about it, I fashioned a hooky type tool out of wire:

One end is a shepherd's crook, the other is a simple L hook and the middle is a loop. So, I ended up using this tool quite a lot today! First job then is to use the shepherd's crook to lift out through the chainstay hole the non-nipple end of a gear cable, inserted into the bottom bracket, like this:

Eagle-eyed readers will see that I snipped off the very end of the sherpherd's crook, to make it easier to pull out of the 6mm hole. Basically, it's like fishing - poke the gear cable with one hand, try to hook it out with the left. It's relatively easy because you can feel the gear cable touch the hook and you can sometimes see it through the hole too. Once that was done, attach the nipple end of another gear cable to the nipple end of this cable. Using masking tape, wrap them up: 

And pull the nipple end through, to end up like this:

Now we're cooking! This nipple end can then be taped to the electrical wire plug:

To create a hinged affair that can fit in a 6mm hole and go around corners. It looks like this:

Which can then be carefully drawn into the chainstay and out of the bottom bracket:

In the photo above, the first electrical wire is installed. A similar technique is used for the head tube - down tube connection. Looking in under the head tube, you can see the gear cable inserted into the entry hole for the down tube:

The gear cable comes out of the BB to the junction box:

The wires going from the seatpost battery to the bottom bracket, and the front mech to the bottom bracket are much easier. And from here, it is quite fiddly to get all your electrical wires where you want them AND to insert the junction box into the down tube, leaving enough space for the bottom bracket itself to be installed. By the way, for this Lynskey recommends copper ease anti-seize and also to PTFE tape the threads on the bottom bracket bearing units. Certainly, I took my time, used lots of patience and avoided frustration by thinking carefully about every step before executing it. 

It shifts like a dream and rides like a magic carpet! Here are some photos of it (I'll cut the steerer down later, after I've settled in on a riding position).