Dahon MuSP: Di2 Shifter and Rear Derailleur

One of the highlights of this new Dahon MuSP is the electronic shifting setup. It is not the first time that I am setting up Di2 electronic shifting on a folding bike, as I have already done it before on the Dahon Boardwalk and Dahon MuEX a few years ago. However, what is new here is internal cable/wire routing for this Dahon MuSP frame, which increases the challenge quite a bit.

Prior to getting these electronic components, I already had the Dahon MuSP frame in hand, in order to study how to set up and assemble the Di2 components onto this frame. I have a plan in mind, but this will be shown in a later post. Only after that was I able to get the required Di2 components, as the set up is rather unconventional.

For this post, let's take a look at the main electronic components, which are the Di2 rear derailleur and the Di2 shifters.

The Ultegra Di2 R8050 rear derailleur is new, as it is a Shadow type road rear derailleur, much like the Dura-Ace R9150 version on the Canyon Endurace. At the same time, it is also styled to look similar to the mechanical version, which is the Ultegra R8000 rear derailleur.

Ultegra Di2 RD-R8050 rear derailleur. Dark grey colour to match most bikes.

Rather strange combination of black and silver bolts here, especially as the black bolt does not match the dark grey colour.

Silver B-tension screw, and the two High and Low limit screws. Easily accessible and visible.

Di2 port is relatively well hidden, behind the main structure and on top of the motor unit. Saver unit also shown here.

View of the cage set. Made of aluminium inner and outer plates.

Inner link shown here with a rough texture, and looks like it is made of glass fibre reinforced plastic.

Weighs 239 grams for this Di2 rear derailleur, which is about 40 grams more than the Dura-Ace Di2 version.

This Ultegra Di2 rear derailleur weighs 40 grams more than the Dura-Ace Di2 rear derailleur, but it is about half the price, with a similar performance as the motor unit looks to be the same. The rational, and more value-for-money choice here would be the Ultegra version, as it is more cost effective compared to the Dura-Ace version.

These shifters are the electronic shifting, mechanical braking version. In other words, it is designed for Di2 shifting, and will be paired with the mechanical road caliper brakes. Although the trend now is for hydraulic disc brakes, it is not suited for this folding bike, which is why I am still using the mechanical brake version.

Ultegra Di2 ST-R8050 electronic shifters with mechanical braking.

Textured rubber hood for better grip and a more high end appearance.

The electronic shift levers have been reshaped and enlarged slightly for better ergonomics.

The tactile feedback of the buttons have also been improved, to give a stronger click feeling, much like the Dura-Ace shifters.

On this Ultegra version, there is even the extra button on top! Previously it was only available on Dura-Ace shifters, but now even Ultegra grade Di2 shifters have it which is really useful.

Hole at the front of the shifter for holding the cast head of the brake inner cable. Also note the grip adjust screw at the left side.

Small hole on the left side is for the brake inner cable to pass through, while the larger brake outer casing will slide into the holding area around the small hole.  

Grip adjust screw located here, which is used to adjust the lever position.

As this shifter will be used by a rider with small hands, the grip adjust screw is turned all the way in, to minimize the reach of the brake lever.

Comparing the position of the lever before and after adjusting the grip adjust screw.

Hidden under the rubber hood are also 3 Di2 ports, which is increased from 2 previously.

This pair of Di2 shifters weigh just 303 grams! Much lighter than the Ultegra 6800 mechanical shifters which weigh 424 grams per pair.

For this new generation of shifters, the hood shape has been adjusted so that regardless of mechanical or Di2 shifting, mechanical or hydraulic braking, the hood should feel similar in the hand. Let's try to compare this Ultegra Di2 shifter with mechanical braking to the Dura-Ace Di2 shifter with hydraulic braking, which is found on the Canyon Endurace.

Comparing the shifters side by side. The hydraulic shifter on the right has a slightly bigger head, but the body size looks similar.

Similar curves on the brake lever, buttons and hood

Appearance comparison from the front. As always, the Dura-Ace lever always looks much more glossy.

Once again, the Ultegra Di2 shifter has practically all of the functions of the Dura-Ace Di2 shifter, except that it weighs a bit more. If you can accept this, then the Ultegra shifters is a much better deal as it is much cheaper than the Dura-Ace shifters.

Dahon MuSP: Crankset and Cassette

On the Dahon MuSP, a front single setup will be used. This means a 1x11 speed drivetrain, which is sufficient for everyday casual riding. My preferred front single crankset would be a Shimano road crankarm with Wolftooth Drop Stop chainring.

From my experience, the 105 5800 crankset is a great choice for setting up a front single crankset. The 105 right crankarm (340 grams) is just slightly heavier than an Ultegra right crankarm (325 grams), but is quite a bit cheaper. However, I want to install a full Ultegra groupset, and not mix the components. Therefore, I still decided to use the new Ultegra R8000 crankset for this setup, even though it is more expensive.

Ultegra R8000 crankset, with the chunky right crankarm as seen here. Similar to the Dura-Ace R9100 crankset used on the Canyon Endurace.

Right crankarm weighs 325 grams, which is only a little bit lighter than the 105 version.

Wolftooth Drop Stop chainring, 46T. This is larger than the 44T chainring which I used on the 451 Wheelsport Fantasy and also Java Freccia mini velo.

Comparing the 46T narrow wide chainring to the original Ultegra R8000 50T chainring

However, with the new chunky crankarm design, it is not a straightforward swap to the Wolftooth chainring, as there is some interference on one of the four arms. Therefore, some cutting and filing is required on the Wolftooth chainring, in order to make it fit on the Ultegra R8000 crankarm.

Special curved profile on the original Ultegra R8000 chainring, to clear the crankarm.

First we need to know which area on the Wolftooth chainring to remove. This can be done by placing the Wolftooth chainring onto the Ultegra chainring, which fits neatly on the chainring bolts.

Once placed together, the area to cut off can be seen here. Need to match the profile on the original Ultegra chainring.

Mark the area to remove with a marker, and either cut or file off the interference area. It was quite a bit of workout, as the chainring is made of heat treated aluminium which is quite hard.

Blue coloured Litepro chainring bolts to match the overall blue theme of the bike. It comes in a set of 5, but only 4 is needed.

With the Wolftooth chainring and blue chainring bolts installed! The blue chainring bolts really stand out.

Right side crankset weighs 426 grams.

Left side Ultegra R8000 crankarm weighs 194 grams.

This gives a total crankset weight of 620 grams, which is considered quite lightweight. Note that the crankarm length for this R8000 crankset is 165mm.

Moving on to the cassette, we will use an Ultegra R8000 11-30T cassette. Previously, when building the Crius AEV20 folding bike, I used an Ultegra R8000 short cage rear derailleur with the 11-32T cassette. The maximum recommended cassette size for short cage rear derailleur is just 30T, not 32T. Therefore, it was difficult to get the rear shifting tuned properly, although it can be done.

This time, I decided that it would be better to stick to the recommended specifications, which means a maximum sprocket size of 30T for the Ultegra Di2 R8050 rear derailleur.

The gear sprocket sizes for the 11-30T cassette is 11-12-13-14-15-17-19-21-24-27-30. This gear range should be sufficient for casual cycling, with more gearing details shown later in this post.

24-27-30 teeth sprockets are mounted on the same aluminium spider

19-21 teeth sprockets are mounted on a carbon fibre spider for lower weight.

In total, the Ultegra R8000 11-30T cassette weighs 270 grams. This is a big increase from the Dura-Ace R9100 11-30T cassette, which weighs only 206 grams.

Cassette installed on the Wheelsport rear wheel! All new and shiny.

With the 11-30T cassette, the gear range is quite wide, and sufficient to handle most conditions. Using the different sized chainrings will just shift the gear range higher or lower.

From my past experience, a 44T chainring is good for 451 wheels, while 48T is used on 406 wheels. Both gives a top gear of 88 gear inches, which is sufficient most of the time. The only time when this top gear is lacking is when we want to pedal down a slope.

This time, I decided to shift the gear range slightly, by using a 46T chainring instead of a 44T chainring for the 451 wheels. As shown below, this yields a higher top gear ratio, at the expense of a higher low gear.

Gear range of 46T chainring with 11-30T cassette, on 451 wheels is 33.7 to 92 gear inches.

At the top gear ratio of 46/11 teeth, a cadence of 100 RPM will move you at 40km/h, which is more than sufficient for a folding bike.

For sustained efforts, if you can maintain 90 RPM at the top gear ratio of 46/11 teeth, your speed will be 36km/h, which is not easy even on a road bike. In other words, this gear range is surely sufficient for the folding bike for casual riding.

Dahon MuSP: Wheelset, Tires and Brakes

Moving on to the second part of the Dahon MuSP build, let's check out the wheelset, tires and the brake calipers.

As I have already used on many bikes, the Wheelsport wheels are a good combination of weight, price and performance. Also, they come in a variety of specifications (406 or 451 size, 74 or 100mm front OLD, rim or disc brakes) and also colours, so they can fit almost any bike you want.

Dahon MuEX: Sunny 406, 74/130mm, Black
Dahon Boardwalk: Smart 1.0 406, 74/130mm, Gold
Crius AEV20: Smart 1.0 406, 74/130mm, Black
Wheelsport Fantasy: Smart 1.0 451, 100/130mm, Black

Therefore, it is a natural choice to get a Wheelsport wheelset again for this new Dahon MuSP folding bike. Also, this is the only brand which has a blue coloured wheelset, which is one of the requirements for this bike.

For the Dahon MuSP, the wheelset specifications that I require would be the Smart 1.0, 451 sized, with 74mm front and 130mm rear OLD. The blue colour specification is not so commonly available, so I had to wait patiently for the blue wheelset to arrive.

Smart 1.0, 451 size, blue colour! The special spoke pattern always makes it stand out from other wheelsets.

Black bladed spokes which looks nicer than standard round spokes. I noticed that the blue on the hub and the rims are a different shade of blue.

Front wheel weighs 580 grams, which is not that lightweight. Mostly due to the 30mm high rim profile.

Rear wheel is 799 grams

This gives a total wheelset weight of 1379 grams! It is a rather average weight for a 451 wheelset, which will surely be heavier than a 406 wheelset as it is larger in size. If you have a more generous budget, you can consider a custom carbon wheelset, which is significantly lighter at around 1100 grams!

Ascent Cirrus Elite Carbon Wheelset

Zefal/Velox cloth rim tape to replace the original plastic rim tape. Slightly thicker and tougher to prevent punctures caused by sharp rim holes.

For 451 tires, there are not many good choices. If you want narrower tires for lighter weight, get the Schwalbe One (23-451), which only weigh 323 grams for a pair.

However, if you want wider tires for more comfort, the Panaracer Minits Lite (28-451) would be a better choice. This is exactly the same one as what I used on the Java Freccia mini velo, before I disassembled it.

Brand new Panaracer Minits Lite tires. I had to get new ones as I had already sold away the previous tires which were very lightly used.

28-451 sized, which is wider for a more comfortable ride.

Average weight of 200 grams each, for 400 grams per pair.

Schwalbe SV7A 451 inner tubes weigh 100 grams each.

Blue Wheelsport wheelset with the Panaracer tires installed!

Lightweight titanium QR axles will be used to reduce the weight slightly.

Front 74mm QR axle weighs 23 grams

Rear 130mm QR axle weighs 27 grams.

This pair of titanium QR axles weigh just 50 grams in total, which is about half the weight of standard steel QR axles.

Moving on to the brake calipers, this is the first time I can install standard reach road brake calipers on a folding bike. Although the stock bike comes with Shimano Sora brake calipers, I wanted to install the full Ultegra groupset, which also has the latest brake caliper design.

Ultegra R8000 road brake calipers. On first look, it may look similar to the previous 6800 version, but it actually has a lot of subtle but important differences.

Quick release lever has been redesigned so that when closed, the tip of the lever is hidden within the brake arm instead of sticking out.

There is no longer a gap on the top brake arm, as the mechanism has been redesigned.

Rear of the brake caliper, with 2 black nuts used.

Cam roller mechanism has been redesigned, to use a stamped steel design to hold the roller. Note the new adjustment screw at the left side (green colour).

Additional steel plate for stiffening the whole brake caliper, by linking up the left and right pivots.

New adjustment screw is located on the side brake arm, instead of at the top arm.

Ultegra R8000 brake calipers weigh 362 grams for a pair, which is a 10% increase compared to the Ultegra 6800 generation. This is due to the additional steel plates for stiffening the brake caliper.

The new Ultegra R8000 brake calipers are reported to have improved brake power, although it comes at the expense of additional weight. I can't wait to install them to try it out!