Hi Everyone, I'm new to the forum, but have been checking it out lately for ideas as I recently bought a Kestrel 4000 LTD. I have an idea of my own that I would like to share. The Kestrel has DA Di2 components, but was not optimally set up when built. Kestrel made 100 of these bikes in 2011 and I bought one that was used, but still completely stock. The aerobars are 3T Mistral. The bike came with the Di2 TT bar end shifters SW-7971, but not with the ST-7971 brake/shifters because the Mistral bar does not have internal routing for Di2 (though other higher end 3T aerobars now do). I've wanted a Kestrel 4000 frame ever since it was (re)introduced as a production model at the end of 2010. The LTD has been optimized for Di2, but why they chose a bar that doesnt internally route Di2 on a top-of-the-line TT bike I will never know. For that price they could have put on a Pro Evo Missile or HED Corsair, but I digress.
The budget I had covered getting the bike at a very reasonable price and allowed me to purchase the ST-7971 separately. It wasnt until I went to install the brake/shifters and pulled out the existing brakes that I realized I was going to need to figure out how to cleanly route the Di2 cable to the brake/shifters. I'm a bit of a perfectionist and after finally getting my dream bike with DA Di2 I want the thing to be sleek, clean, and mean, and not half-assed. I cant afford to spend another $500-$1000 right now on a new base bar/cockpit that has Di2 fully routed internally, plus I dont want to mess with the position I've dialed in right before I start racing this season. So that got me thinking this week and here is what I have come up with for my DIY Di2 ST-7971 cable routing for the 3T Mistral (and any base bar that is not Di2 internally routed).
After getting the connectors covered with heat shrink tubing I taped the Di2 cable to the bullhorn on the Mistral. The connector sits about 3/4s of the way towards the back of the bullhorn. There is enough clearance for me to grip the bullhorn when braking or shifting without feeling the protruding connector under the bar tape, but if I'm climbing and want to slide my hand rearward at all its really bulky and feels weird. Basically you know the connector is under there. The bullhorns on the Mistral seem longer than most TT base bars and if they were shorter the Di2 connector would sit directly underneath part of the base wing and not extend out to the bullhorns, and therefore be completely out of the way of the grip. Part A of this project was to cut the bullhorns down, since there seems to be a longer handle than really necessary on a TT base bar. This is pretty simple to do if you have ever cut carbon fiber extensions. I used a fine-tooth hacksaw, wrapped the bullhorn in tape and lopped off about 1.5" from each.
With the bullhorns cut down part B of the project was to secure the Di2 cable to the rear edge underneath the wing where it would not disturb the airflow. I tried taping it down with electrical tape, and this does the job, but it doesnt look all that great, and with electrical tape the potential is there for it to start sliding around if it gets wet or heats up in the sun, and it gets all gooey and nasty. I wanted to keep the aerodynamics of the base wing as unaltered as possible and use something that wouldnt have the issues with tape. I came up with using liquid rubber. You can get it in a can that can be sprayed or it can be brushed on. I've tried Plasti-Dip. It easily adheres to painted surfaces and can be easily removed if you ever want to take it off without damaging the paint.
Using masking tape I taped a channel where I wanted to lay the Di2 cable and then 'tacked' a small area with the spray at the junction of the bullhorn and wing to hold the cable in place. Once this tacked area set up a little I then sprayed the entire length of the cable on the underside of the wing. This will hold the cable securely in place giving it a protective coating in case it gets scraped in any way. The heat shrink tubing provides good protection for the connector joins and I sprayed right up this. I did not used the dual walled tubing because you can use the liquid rubber to seal the ends of the heat shrink tube around the cable and the regular heat shrink tubing can easily be removed. I left the connectors uncovered by the liquid rubber so I can easily get at them should I need to take the shifter off. The liquid rubber will just peel away if you want to remove the entire cable from the bar.
For the cost of the liquid rubber can I was able to keep my position the way I wanted with this particular aerobar and not spend hundreds on a new one and have to try to get the position to match or get used to a new position. Maybe I'll replace the Mistral at some point with a newer 3T bar that has internal routing, but for now this seems like its going to work really well.