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!

Click here for Part 3!

Dahon MuEX: Compatibility Checking for 10 Speed Ultegra/XTR Di2

As part of the consideration when I recently upgraded the Dahon Boardwalk from 10 speed to 11 speed, one of the reasons was to free up the 10 speed Di2 components for another bike. This other bike would be the Dahon MuEX!

The Dahon MuEX was first built to prove that it is possible to build a high performance and lightweight folding bike at an affordable price. This project was successfully completed, with a 20 speed, 9.4kg folding bike costing $1700.

With the launch of the new XTR M9050 Di2 system, there is a component which caught my eye, and that is the new electronic shifter. These are flat handlebar Di2 shifters for the XTR Di2 groupset, but it can also be used with other Di2 components. It would be really interesting to try out these shifters and see how well it works on a flat handlebar Di2 bike.

Shimano XTR Di2 Firebolt Shifters, SW-M9050 

As shown by this compatibility chart, it is possible to match these Di2 shifters with other road components, such as the 10 speed Ultegra 6770 Di2 components.

Of course, before purchasing all the required components, it is necessary to ensure that all the components will work and fit on the MuEX frame. Prior to upgrading the Dahon Boardwalk from 10 to 11 speeds, I had already tried out installing the 10 speed Ultegra 6770 Di2 components on the MuEX frame. The major concern I had was whether the bulky Ultegra 6770 Di2 front derailleur will fit on the MuEX frame.

Testing out the Ultegra 6770 Di2 Front Derailleur on the MuEX frame.

Very small gap between the FD and the frame!

Also, very small gap between the FD and the right crank arm. The solution is to add a BB spacer under the right side BB adapter to push out the crank a bit more.

As can be seen from the pictures above, the FD barely fits onto the MuEX frame, and it has very small clearances with the frame and the crank arm. I had previously found that the FD hanger seems to be welded slightly too far out from the frame seat tube, which contributed to these scenarios. In a way, this is good as it gave sufficient clearance between the frame and the FD. As for the clearance between the FD and the right crank arm, it can be increased by adding a BB spacer to push the right crank arm slightly further outwards.

As for the FD support bolt, I found that it seems to be slightly too short to reach the frame. This support bolt is supposed to touch the frame, to stiffen up the FD and give better shifting.

FD support bolt which can be found on Di2 FD and new Shimano mechanical FD

The solution is to find a longer set screw (M4) to replace the original support bolt (shown on the left)

Now that the FD mounting is no longer a problem, let us check the other components. The rear derailleur will go on as per normal, no special mounting or clearance issues. Same for the XTR Di2 shifters. As for the mounting of the Junction B and the Di2 wire routing, I can follow the setup used on the Dahon Boardwalk, so no problem there.

This leaves the mounting of the Di2 battery as the major problem here. On the Dahon Boardwalk, I used 2 FD adapter clamps on the frame of the Boardwalk to create a fixing point for the battery mount. However, I cannot do the same on the MuEX frame as the frame shape is not cylindrical.

Di2 battery mounting on the Dahon Boardwalk, created by 2 FD adapter clamps.

In this case, the only way is to create my own mounting point for the Di2 battery mount. What it needs is just two threaded M4 holes that are spaced about 33-42mm apart. My idea is to take an aluminium block, tap the M4 threads, and have slots to allow the DIY mount to be tied to the MuEX frame.

Aluminium block, with two M4 threaded holes, and 2 crude slots for inserting cable ties. The block was spray painted black after the machining work was completed.

Fits the battery mount nicely!

Two gaps underneath for inserting the cable ties through

Testing the DIY battery mount on the MuEX frame

A rubber shim was added between the DIY battery mount and the frame, and then the whole thing was tied to the frame using cable ties. This mount is actually quite secure as it does not move around even when the bike lands hard on the ground. Seems that it will work!

Now that the key components have been checked for compatibility with the Dahon MuEX frame, the next step is to gather all the required components and update the firmware, before installing them onto the frame. To be continued!

Click here for Part 2!

Difference between Ultegra 6770 Di2 and Ultegra 6870 Di2

Now that all the top end groupsets are moving towards 11 speeds, Shimano Di2 components have also been upgraded from 10 to 11 speeds. For Ultegra Di2, it has changed from the first generation 10 speed Ultegra 6770 to the latest generation of 11 speed Ultegra Di2 6870. On the Dahon Boardwalk, I have also installed Ultegra Di2 6870.

This new generation of Ultegra 6870 Di2 has been refined and improved from the previous generation of Di2 components. The main differences are in the rear derailleur and front derailleur, with only minor changes to the shifters. Let's take a closer look at the old and new Ultegra Di2 RD and FD, and see the differences and similarities.

New Ultegra Di2 6870 FD, 138 grams

 Old Ultegra Di2 6770 FD, 167 grams. Heavier by almost 30 grams.

Old FD on the left, new FD on the right. The new FD is much smaller in size!

The difference in size of the servo motor, as seen by the size of the casing

New FD is shorter and more compact

Comparing the size from the rear

Another picture comparing the size of the servo motor. This new Ultegra Di2 FD is similar in size to the Dura-Ace Di2 FD.

Some hollow rivets are used for the new FD as shown on the right side

Wire connection port on the new FD is located at a more hidden location

See the difference in the wire routing. Wire for the new FD exits at the rear, which makes it neater than the old FD.

The major difference for the Ultegra Di2 FD would be the size of the FD. This new generation of Ultegra 6870 Di2 FD is much smaller in size than the previous generation. Now, the Ultegra Di2 FD is similar in size to the Dura-Ace FD, which is great.

Another difference is the wire routing, which is neater on the new FD, as it exits at the rear-bottom, and can be well hidden by the frame. Other than these differences, the other parts of the new FD look similar to the old design.

Next, we will compare the old Ultegra Di2 6770 10 speed RD to the new Ultegra Di2 6870 11 speed RD.

New Ultegra Di2 6870 11 speed RD, 256 grams

Old Ultegra Di2 6770 10 speed RD, 272 grams.

Obvious difference in size between the new RD on the left and the old RD on the right

The servo motor on the old RD is much larger than on the new RD!

The old RD sticks out a lot more than the new RD

The limit screws have been moved from the bottom to the top of the RD 

The linkages have been changed, with the crash protection arm located at the bottom of the new RD instead of at the top for the old RD

Close up look at the crash protection arm on the new RD

For the old RD, the limit screws are located at the bottom, together with the stopper plate of the RD. 

Similar to the FD, the main difference for the RD would be the size. As seen from the pictures above, the new RD is much smaller in size than the old RD. In fact, it is similar in size to the new Dura-Ace Di2 9070 RD. All other parts look quite similar, and the wire connection port is also located at the same area on top.

In summary, for this new generation of Ultegra Di2 6870 RD and FD, the component sizes have been greatly reduced compared to the previous 6770 generation. The sizes are now very similar to the Dura-Ace Di2 9070 components, which is really good. This makes the Ultegra Di2 components a very good deal, as the performance and size is similar to Dura-Ace, and yet is available at half the price of Dura-Ace.