The Big Build
A Step by Step Guide into Our Latest Build
Scott Plasma 3 TT Di2
Our latest project is about to start and we thought we would give you an insight in to the stage of the build from start to finish.
Our latest build will take one of the the best Time Trial/ Triathlon frames in the world complete with a full internal Shimano Ultegra Di2 6870 (11 speed) groupset. It will be of a similar specification to our previous Scott Plasma 3 TT build (which can be found here).
We will be updating this post regularly throughout the build. Feel free to ask any questions you may have regarding the build process, or if you are interested in buying the finished bike, then please contact us using our contact form.
The Frame
The Scott Plasma 3 TT Di2 specific full carbon fibre frame complete with front brake cable outer sleeve (factory fitted) and Shimano Dura-Ace 7800 (frame specific) rear brake caliper (fitted by us).
Di2 Internal Cabling Installation
First we install the Di2 internal cabling, this is not a complicated task but can be fiddly. We start by removing the access panel above the bottom bracket and then feed through 4No. Di2 EW-SD50 ETube electric wires which connect using the SM-JC41 (internal) junction box.
Choosing the best length cable to run to each component is important to allow sufficient slack for future maintenance, we have chosen the following:
Internal Battery (SM-BTR2-1) to SM-JC41 - 800mm
Rear Derailleur (RD-6870-SS) to SM-JC41 - 650mm
Head Tube to SMJC41 - 1400mm
Front Derailleur (FD-6870) to SM-JC41 - 300mm
Bottom Bracket Installation
Before purchasing your bottom bracket you need to check which type is required to suit your frame and chainset. The bottom bracket we have used for this build is the Shimano Dura-Ace push fit to suit our Shimano Ultegra Hollowtech 2 chainset.
Before inserting the bottom bracket into its housing you need to ensure that there is no Di2 cabling dropping into the area of the bottom bracket chamber, this can be pushed up into the bottom of the vertical down post. Before you insert the bottom bracket ensure that you are inserting in the correct way, on the main body of the bottom bracket there is a demarcation indicating the left and right sides this can be seen in the image below.
Once the bottom bracket has been inserted it is not quite as simple as 'pushing it to fit' you will need a tool to do this. You can make a simple too from threaded rod and bolts however, we have used the tool that Shimano provide for mere extortionate price of £40. Once you have placed the tool through the bottom bracket carefully wind the tool using a spanner and hex key until the outer face of the bottom bracket is flush with the frame. Finally you can then pull fix the access panel back to the frame ensuring that the Di2 cable for the front derailleur is slotted through the gap provided.
Front Fork and Headset Installation
The bike comes complete with the headset bearings as pictured in Figure 1 below. However, unlike most other bikes, the installation of the fork is complicated as a result of the rear brake cable and Di2 cable to the bottom junction box actually running through the steerer tube of the forks.
figure 1 figure 2 figure 3
In order to install the forks, you must first install the lower headset bearing (the fork crown race is built into the forks on this bike, so the bottom bearings simply drop onto the steerer tube (Figure 2). The rear brake cable outer housing and Di2 cable then need to be pulled through from the top of the steerer tube to the bottom, as shown in Figure 3 above.
figure 4 figure 5 figure 6
Next, thread the rear brake cable housing and Di2 cable through the hole on the back of the steerer tube and up out of the steerer tube (Figure 4), then thread the fork steerer tube with cable up through the head tube, gently pushing the brake housing and Di2 cable with it to avoid damaging them (Figure 5). Once through, install the upper bearing over the cables and steerer tube, then gently push the rear brake cable housing and Di2 cable back down and out through the top front hole of the steerer tube, ready for installation into the bars (Figure 6).
Handle Bar Installation Part 1: Assembly
The Plasma 3 TT frameset comes complete with the flat 'shark tooth' stem and colour matched PRO Missile Evo full carbon bars. The beauty of Di2 is that it enables shifting from both the base bar (bull horns) AND the TT extensions (this is not possible with mechanical shifting systems). However, installing the four Di2 cables and two brake cables is quite onerous, especially when the PRO Missile Evo 'riser kit' (shown here in the narrow setup) are also used as the Di2 cables are run fully internally through the bars and feed out straight into the stem. We used flexible plastic tubes to daw string through the bars, then used the string to pull the Di2 cables through. This may sound simple but it's quite complex and you need to take your time and you'll eventually get all of the cables through.
The photos above and below show the bars once all of the various shifters, brake levers/shifters, Di2 cables and brake cables have been installed. The cables are ready to be run into the stem for connection to the 5 port junction box which will be fitted just beneath the stem. The TT shifters (for the extensions) used where the Shimano SW-R671 Di2, and for the drop down bars we used the dual shifter and brake lever Shimano Ultegra ST-6871 Di2 (these differ from the Dura-Ace brake lever/shifter that look very similar as the Dura-Ace version have carbon fibre levers compared to the Ultegra which have aluminium).
Handlebar Installation Part 2: Stem Installation and handlebar mounting
Above are shown the complete 'shark tooth' stem (as used with this frameset on the pro team bikes), an exploded view of the stem and a close up of the unusual top cap, bolt and metal bar that sits in the steerer tube and is used to preload the headset bearings.
To install the stem the bar is slotted across the steerer tube (above left). This needs to be inserted with the chamfered end facing the font of the bike as it allows clearance for the cables running up from the frame to come through into the stem. This cables are shown in the middle and right photos once the top cap is installed and tightened (just enough to load the headset bearings), using the small bolt. The four bolts on the back of the stem should then be tightened with the stem facing forward.
The pre-wired bars are then installed with the rear brake cable being run into and through the bike frame via the rear brake cable housing (above left). The four Di2 cables and the brake cable with housing are then all fed through the hole in the bottom of the stem to serve a) the 5 port Di2 junction box (which also requires the Di2 cable from the frame to be fed through and also connected), and b) the front brake cable with housing.
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