Wednesday, December 27, 2017

Dahon MuEX: 1x11 Drivetrain - Installation

Finally, after preparing the 11-32T 11 speed cassette, the short cage Ultegra Di2 rear derailleur, and the front single Ultegra 6800 crankset with Wolf Tooth 48T chainring, it is time to assemble all these new components to the Dahon MuEX!

It was already set up with a 2x10 speed Ultegra/XTR Di2 system, so there is no need to start from scratch. The advantage of having a Di2 setup is that it is modular. So if you just need to upgrade the rear derailleur, just unplug and replace the rear derailleur, and you are done! No need to change the shifters or the Di2 wires.

In this case, since I am going from a front double to front single drivetrain, the front derailleur can be removed, along with the left side shifter. The new Di2 wiring layout is shown below.

New 1x11 speed Di2 wiring layout. No more front derailleur or left side shifter.

Once everything is connected, the Di2 setup box SM-PCE1 can be connected to the system to update all the Di2 components. This ensures that the latest firmware is used and all the components are compatible with one another.

Previously, when the Ultegra Di2 front derailleur was installed, a 2.5mm spacer had to be placed under the right side bottom bracket cup to prevent the crankarm from touching the front derailleur. Now, without the front derailleur, there is no need for this spacer.

Red 2.5mm spacer under the right side bottom bracket cup can be removed.

Ultegra 6800 crankset with Wolf Tooth 48T chainring installed! Looks really good with the red chainring bolts.

Close up look of the interface between the chainring and the crankarm.

Front derailleur removed!

Ultegra 6800 11-32T 11 speed cassette installed!

Special short cage edition Ultegra Di2 RD-6870 rear derailleur for 11-32T cassette. Very ample tire and ground clearance.

Chain path when in the rear low gear. Rear derailleur cage is not over stretched even though it is a short cage, because there is only one front chainring.

Good clearance between cage/chain with tire

Another view of the clearance.

Setting the chain to the rear top gear puts the chain in the smallest sprocket, closest to the frame. Still ample clearance between chain and frame.

Chain path when in the rear top gear. Rear derailleur cage is slightly extended to maintain some chain tension to minimize chain slap.

Another view of the Di2 rear derailleur on the cassette.

Handlebar gets tidied up a bit, without the left side shifter and the Di2 wire between the left side shifter and the display.

Now it is 11 speed as shown on the display! I love the digital gear display, like how I first tried it on the Dahon Boardwalk Di2.

The bell can be mounted at the left side handlebar area, inverted for a neater look. Activate the bell by pulling the bell lever with the index finger, similar to how a shifter is operated.

No interference between the bell and other parts when the handlebar is folded down

Sufficient clearance for the bell when the bike is folded

View of the folded Dahon MuEX 1x11 speed

View from the drive side 

View from the non-drive side

For practical reasons, a kickstand is added to the bike despite the additional weight. Kickstand weighs about 157 grams.

Revised bike specifications, with the new 1x11 speed Di2 setup. Weight without pedals is reduced from 8.7 kg to 8.4 kg.

This setup has already been tested at the recent OCBC Cycle 2017, and there is no problem! The gear range is sufficient for climbing and also a bit of downslope pedaling. Of course, if you wish to pedal fast down the Sheares bridge slope, the gearing is not high enough. On all other days, this gearing is sufficient 99% of the time.

Gear shifting has been simplified, as there is just one shifter to shift across the 11 speeds on the rear cassette. The overall bike weight has also been reduced, due to the removal of the left shifter, front derailleur and second chainring. Even though the wide range cassette is slightly heavier, overall weight loss is still about 300 grams. Lastly, I get to utilize the components that were removed from the Canyon Endurace, using it to convert this Dahon bike to 11 speeds.

Thursday, December 21, 2017

Dahon MuEX: 1x11 Drivetrain - Wolf Tooth 48T Chainring on Ultegra 6800 Crankset

After successfully modifying the 11 speed 11-32T cassette and the Ultegra Di2 rear derailleur, the only component remaining that needs to be prepared is the front single crankset.

The Dahon MuEX currently has a 2x10 speed drivetrain, and it is using the Ultegra 6700 53/39T crankset that is designed for 2x10 speed. Converting it to a single chainring is easy, as I will just need to get a narrow wide chainring that has a 130mm BCD to fit the crank arm.

However, I decided to use the newer Ultegra 6800 crankset from the Canyon Endurace instead. Function wise, there should be no difference regardless of the crankset used. In this case I prefer to use the Ultegra 6800 crankset as it will be of the same series as the Ultegra Di2 RD-6870.

Picture taken from a magazine. Looks good!

What I will require will be a narrow wide chainring, to replace the double chainrings on the Ultegra 6800 crankset. As previously tested successfully, the Wolf Tooth narrow wide chainring is an excellent choice. The 4 arm design of the chainring matches the 4 arm crankset quite nicely, while the narrow wide teeth design eliminates chain drop issues.

For this bike, I decided to go with a 48T chainring, which will give me a similar gear range as the 2x10 speed setup when used with the 11-32T cassette. This chainring size was not available in the Shimano road 4 arm design until recently, which was what allowed this project to proceed.

Wolf Tooth 48T narrow wide chainring, designed to fit the Shimano road 4 arm crankset.

Specifications laser marked onto the chainring for easy identification

Narrow wide teeth design improves chain retention, eliminating the need for a chain guard to prevent chain drops.

Thicker chainring bolt mounting area to allow the bolt head to be recessed, while also improving appearance with the crankarm.

Slight appearance difference with the older 44T chainring, as there is no step but instead has a smooth transition between the hole and the teeth area.

Weighs 103 grams. Not much lighter compared to the Hollowglide chainring.

Red anodized aluminium chainring bolts by LitePro.

Perfect chainring nut length. Just below the flat surface where the bolt head will rest on. A little grease helps to prevent the threads from seizing.

Chainring and bolts installed!

Looks super good! Black chainring on the dark grey crankarm, with red chainring bolts to match the other red highlights on the Dahon MuEX setup.

Right side crankarm set weighs 441 grams

No change to the left side crankarm, weighs 197 grams including the plastic crank arm fixing bolt.

This gives a total crankset weight of 638 grams, which is an average weight for a front single crankset. There are lighter setups out there, some of which may actually be cheaper, such as those from LitePro or Ridea. However, I still prefer to use the Ultegra crankset to match the Ultegra rear derailleur.

Since all the 3 key components have been prepared (11-32T cassette, Ultegra Di2 rear derailleur, 48T front single crankset), the next step would be to install all these components onto the Dahon MuEX. Check out the details of the installation in the next blog post!

Saturday, December 16, 2017

Dahon MuEX: 1x11 Drivetrain - Ultegra Di2 RD Cage Modification

This project's objective is to convert the drivetrain on the Dahon MuEX from 2x10 speed to 1x11 speed. The most challenging part of this project is to install the 11 speed 11-32T cassette onto the 10 speed freehub body of the Kinetix Pro wheelset. With that successfully done, it is now possible to continue this project.

As the rear cassette gets upgraded from 10 to 11 speed, the Di2 rear derailleur also needs to be upgraded to match the same number of speeds. Unfortunately the rear derailleur cannot be simply reprogrammed to work for 11 speeds, therefore a change is necessary. The current 10 speed Ultegra Di2 RD-6770 will be replaced with the newer 11 speed Ultegra Di2 RD-6870 from the Canyon Endurace.

This Ultegra Di2 RD-6870 is the mid cage version, as it was chosen to be compatible with the 11-32T cassette. The more common short cage version can only work properly up to 28T sprockets.

Not only is the cage length different, the design of the linkage and other parts are also slightly different. This is to account for the different cassette shape as it moves from the smallest 11T to the largest 28T or 32T sprocket. As shown below, most parts are the same, but the Plate Member is different which affects the guide pulley position and movement.

Ultegra Di2 RD-6870: Difference between Mid and Short Cage versions

In other words, if you use a short cage version for a 11-32T cassette, or a mid cage version for a close ratio cassette (such as 11-25T), shifting performance may be compromised. If you have a 11-28T sprocket, I think either the short or mid cage version will be OK.

As for the longer cage on the mid cage version, it is longer because it needs more chain slack capacity, as the chain difference is greater on a 11-32T cassette than on a 11-28T or smaller cassette.

Chain capacity required = (Front max - front min) + (Rear max - rear min)

On the stock Canyon Endurace, the front crankset is 52/36T while the cassette is 11-32T. Using the formula above, the chain capacity required would be (52 - 36) + (32 - 11) = 37T, exactly the maximum that the mid cage rear derailleur can support.

Ultegra Di2 RD-6870-GS, which is the mid cage version. This is different from the short cage version which I had previously.

The mid cage version has a longer cage to increase the chain capacity, allowing it to be used on a drivetrain with a larger difference between the smallest and biggest gears.

At this point, we have verified that the mid cage rear derailleur is suitable for use with the 11-32T cassette. If they are both installed on the Dahon MuEX, they will work fine, and I can move on to the other components. However, are there any other issues, and is there any room for improvement?

One main problem of using mid or long cage rear derailleurs on small wheeled bikes is the decreased ground clearance and tire clearance. Due to the smaller wheels, the rear derailleur cage will be closer to the ground and also the tire. There is usually no issue with ground clearance, as you will not be taking the small wheeled bike off-road onto uneven ground. On flat ground there is no issue with ground clearance, even when going over humps.

However, tire clearance can be an issue, especially if you have wider tires, such as the Schwalbe Kojak. When the rear derailleur is shifted to the lowest gear, it is close to the spokes and also the tire. From my previous experience on modifying small wheeled bikes, using a road mid cage rear derailleur on 20" wheels with wide tires will leave quite a small clearance between the cage and tire. It will still work with no interference, but it gets a bit too close for my comfort.

On a normal drivetrain with a front double crankset, the mid cage is necessary to provide sufficient chain capacity. However, since this will be a front single 1x11 speed drivetrain, the front chainring will always be the same size as there is no front shifting.

Referring to the formula again for chain capacity,
Chain capacity required = (Front max - front min) + (Rear max - rear min)

If the front chainring is fixed at a certain size, the chain capacity thus depends solely on the rear cassette size. 32T (max) - 11T (min) = 21T. Only 21T of chain capacity is required if a front single chainring is used, which can be satisfied even with a super short cage (which does not exist).

In other words, a rear derailleur with a short cage will have sufficient capacity to satisfy a front single setup. In this case, if I take the mid cage RD-6870, and change just the cage to a short cage, I will get a rear derailleur that is compatible with the 11-32T cassette but with reduced chain capacity. This is not a problem for this front single drivetrain, but the advantage is that I get more ground and tire clearance, while it is also a little more lightweight.

Which rear derailleur cage is compatible? From the exploded view diagrams of the RD-6870, you can see what parts are interchangeable or compatible.

Exploded view of the Ultegra Di2 RD-6870. This only shows the user replaceable parts, which are mainly the components of the cage.

From this table, I found that the cage set components (inner and outer plate) are basically interchangeable with the mechanical Ultegra RD-6800 rear derailleur.

Therefore, I will need to cannibalize a short cage from the mechanical Ultegra rear derailleur, RD-6800. If you prefer, you can order spare parts from Shimano, and buy just the short cage set. However, this is more troublesome and you have no idea how long this part will take to arrive.

Short cage mechanical RD-6800 on the left, mid cage Di2 RD-6870 on the right. The idea is to move the short cage over.

To swap the cage set, the bolt shown here needs to be removed to detach the cage set. Before that, the guide pulley needs to be removed to access this bolt.

Before dismantling the mid cage Ultegra Di2 RD-6870, it is weighed for reference. About 268 grams with the mid cage.

Mid cage parts dismantled from the Di2 RD-6870

Short cage parts dismantled from the mechanical RD-6800

As the cage parts are compatible and similar, it is a straightforward swap. With this modification, I get a short cage Di2 RD-6870 that is capable of shifting well even up to a 11-32T cassette. The other combination (mechanical RD-6800 with higher chain capacity, but is only compatible up to 11-28T cassette) is not that useful, although it can still be used normally, just with a longer-than-necessary cage.

Special edition Ultegra Di2 RD-6870 with a hybrid of mid cage design and short cage capacity.

With the short cage, the rear derailleur looks more compact

After changing to the short cage, this rear derailleur now weighs about 10 grams less at 258 grams.

The objective of going through all this hassle is to get a short cage version of the Ultegra Di2 RD-6870 that can shift well up to the large 32T sprocket. It will have better tire and ground clearance when installed on the 20" Dahon MuEX folding bike.

After completing the modification of the 11 speed 11-32T cassette, followed by this special edition rear derailleur, the next step is to convert the Ultegra crankset to a front single crankset.