Friday, July 31, 2015

Dahon MuEX: Components for 10 Speed Ultegra/XTR Di2

In the previous part of the Dahon MuEX upgrade, I have confirmed the feasibility of installing the Ultegra Di2 6770 Front Derailleur and the Di2 battery onto the MuEX frame. Now that the major compatibility concerns have been addressed, I will now gather and study all the required components before installing them onto the bike.

One of the key component for this new Ultegra/XTR Di2 hybrid build is the new XTR Di2 Firebolt shifters. These XTR Di2 shifters are totally different from any other shifters, as the operation method is completely new. The levers/buttons revolves around the handlebar, with the centre of the handlebar as the rotation axis. This is more ergonomic as it follows the natural movement of the thumb, allowing for a shorter shifting stroke and a more comfortable way of operating the shifting levers. Let us now take a closer look at these new shifters!

Shimano XTR Di2 Firebolt shifters, SW-M9050. Can be used as a pair or just one side, depending on setup.

Two textured buttons for shifting up and down. As these are just electronic buttons, they can be programmed to work either way, much like how the road Di2 system can be configured.

The position of the two buttons can be individually adjusted according to preference, by moving the button along the slot as shown.

Instead of a standard clamp like those on flat handlebar shifters, this Di2 shifter uses a screw at the side to tighten the shifter onto the handlebar. Note that this is not a set screw that bites into the handlebar, but it moves a metal plate that presses onto the handlebar, and thus will not damage carbon handlebars.

As these XTR Di2 shifters are designed primarily for mountain bike usage, it is important to have some sort of shifting feedback in the form of a positive click for each gear engagement. For road Di2 shifters, the click is quite subtle, which is OK for road bikes but not for mountain bikes. Therefore, there is a clicking mechanism that is specially built into these XTR Di2 shifters to give the strong clicky feeling during a shift.

Spring mechanism that is built into the XTR Di2 shifter, with the sole purpose of giving the shifter a clicky feel during shifts. 

This pair of Di2 shifters weigh only 128 grams, which is much lighter than a pair of mechanical shifters.

Next, I will also need a Junction A for this Di2 system. The purpose of Junction A is to link up the two shifters, and connect them to Junction B and the rest of the Di2 components. From the Di2 compatibility table, I can see that there are a few different types of Junction A to choose from. I used the Road Di2 compatibility table for reference, as the Ultegra rear derailleur and front derailleur that I have means that this hybrid Ultegra/XTR Di2 setup is classified under the Road Di2 system.

Road Di2 compatibility table.

The types of Junction A that I can choose from are the Ultegra road type (EW67), Alfine Di2 Digital Gear Display (SC-S705), the 3 or 5 port type (EW90-A/B), or the XTR Di2 System Display (SC-M9050). I decided to choose the XTR Di2 System Display, because it can display both the front and rear gears, the battery level, and it matches well with the XTR Di2 shifters.

Shimano XTR Di2 System Display, SC-M9050.

Nice and modern looking display, and it comes with two clamp bands. 31.8mm and 35mm clamp diameter.

Resin composite clamp band for weight savings. No need for a metal clamp band as there is no load acting on the display during normal usage.

Displays the Shift Mode (for MTB Di2), Gear and the Suspension Mode (for MTB Di2)

Battery charging port at the side of the display. However, it can only be used with the newer Di2 batteries, such as the external MTB type or the internal seatpost type.

Three ports at the rear of the display. Two of them will be connected to the two Di2 shifters, while the remaining one will be connected to Junction B.

The XTR Di2 System Display is lightweight at only 30 grams. It functions both as a Junction A and also as a digital gear display.

Manual of the Di2 System Display, showing the different features. The battery level and the selected gears (front and rear) can be displayed. No use for Shift Mode or Sus Mode as those are for MTB Di2 systems only.

If used in a MTB Di2 system, the display will have a lot more functions, such as changing the shifting mode or controlling the suspension mode electronically.

With the XTR Di2 shifters and System Display prepared, the other components that are required would be the rest of the Di2 system. As this is a new system, I will need a new Junction B and new Di2 wires.

Junction B for Di2 systems, internal type. I plan to attach it to the frame in the same way as on the Dahon Boardwalk.

All the Di2 components are ready for installation! The Ultegra Di2 6770 RD and FD are taken from the Dahon Boardwalk.

New Di2 wires to link up all the components

New wires of various lengths, with the lengths estimated using prior experience from setting up Di2 on the Dahon Boardwalk

All the components for installing the Ultegra/XTR Di2 system have been gathered, and the next step is to update the firmware for all these components. After that, they can be installed on the Dahon MuEX!


  1. Great post! Could you get away with connecting the XTR SW-M9050 shifters to the existing Ultegra EW67?