Wednesday, June 27, 2018

Crius AEV20 1x11: Drivetrain Selection

As I am building a folding bike from scratch, I can choose every component that will be assembled onto the bike. From the Crius frameset to the Wheelsport wheels, everything can be customized.

The drivetrain selection plays a big role in determining how well the bike will ride and shift. Therefore, I like to choose proven components that will work well, even though it may not be the lightest. There is usually also a budget constraint, so it cannot be the top level model as well, it needs to be affordable.

When I think of these three things: 1) Functions well / 2) Reasonable weight / 3) Affordable, the Shimano 105 groupset comes to my mind. Being the third tier road groupset, after Ultegra and Dura-Ace, it is relatively affordable, and yet performs well and close enough to the higher end components.

The newest 105 R7000 groupset was recently announced, and it looks to be really good. In fact, the all black finishing on the new R7000 will really match well with this bike's all-black theme. However, it is not available in the market yet, so I have to choose something else.

For choice of crankset, since this is going to be a 1x11 speed setup, I will go with a 105 5800 crankset, plus the proven Wolftooth Drop Stop narrow wide chainring, which I have used on the Dahon MuEX and the Java Freccia mini velo.

The Ultegra R8000 crankset seems to be all black also, but at twice the price of the outgoing 105 5800 crankset, I cannot justify the price difference. Besides, I am mainly using the crankarms only, the chainrings, however nice, will not be used for this 1x11 speed setup.

Right side crankarm alone weighs 340 grams.

Left side crankarm plus the plastic crank arm fixing bolt weighs 205 grams.

The full front single crankset thus weighs 655 grams. Not really lightweight, as there are lighter combinations out there. However, I like to stick to proven stuff that assembles and functions without fuss.

Wolftooth 48T Drop Stop chainring. Expensive stuff, but looks good and works really well.

All black, as requested!

105 5800 crankset with Wolftooth 48T chainring.

The cheap and good SM-BBR60 Hollowtech II road bottom bracket.

Moving to the rear derailleur, this is where I dared and wanted to pick something untested. I had a choice of picking the 105 5800 rear derailleur, which is affordable and good. However, I wondered how a Shadow road rear derailleur will look and function on a 20 inch folding bike?

The Shadow road rear derailleur was introduced with the latest generation of road bike groupsets, starting from Dura-Ace R9100, then to Ultegra R8000 and the new 105 R7000 series. However, as stated, R7000 was not available yet. Dura-Ace is all black, but out of the question as it is so much more expensive. That said, I did use the Dura-Ace R9150 Di2 rear derailleur on my road bike...

That leaves the only choice to be the Ultegra R8000 rear derailleur. Although I plan to use it with a 11-32T cassette, I chose the short cage version (which is rated up to 30T), so I hope it will work. I did not want to use the mid cage version as the longer cage might interfere with the wide Kojak tires.

Ultegra R8000 Shadow rear derailleur, short cage version. Looks very much like the mountain bike derailleurs.

With an interesting looking new cable adjust construction, designed to look slimmer to match road bikes.

You may have realised that many mountain bike Shadow rear derailleurs (Deore and above) do not have cable adjust bolts on the rear derailleur. This is because there is already a cable adjust bolt at the flat handlebar shifter, so the one on the rear derailleur can be left out.

However, on road drop bar shifters, there is no cable adjust bolt. So it is a good idea to have one on the rear derailleur, else an inline cable adjust will be required.

Very low side profile as you can see! This is the most outward position, and it is barely protruding from the bracket of the rear derailleur.

Black plastic sleeve to guide and protect the inner cable during shifting.

Cable fixing bolt

Weighs just 198 grams!

I am quite impressed with the low weight of the rear derailleur, because the Shadow construction looks rather chunky and looks like it might weigh more than the shorter cage Ultegra 6800 rear derailleur.

Comes with a special short length of outer casing, with a metal cap on one end and a cap with tongue on the other side.

The end with the metal cap needs to be inserted at the rear derailleur end, not the frame.

Instructions printed on the box of the rear derailleur. Should only cut the outer casing at the end with the plastic cap, not the metal cap.

The problem with this instructions is that I am unable to follow it when I build this folding bike. Since there will be a long full outer casing from the shifter to the rear derailleur, I cannot use this short section at all. Most likely I can only use the metal cap...

Finally, for good shifting performance, the choice of cassette is also crucial. As this is a front single setup, it is important to select a cassette with a wide enough range for city usage. This means a 11-32T or a 11-34T cassette.

As already mentioned in a separate post, the 11-34T cassette has a big jump from 11T to 13T, which is really not ideal for a comfortable gear step. This means the 11-32T cassette is the best choice for a relatively wide gear range.

Once again, I could choose between the 105 5800 or the Ultegra 6800 11-32T cassette. The main difference is weight and cost. I decided to get the cheaper 105 cassette as I already went over budget with the Ultegra R8000 rear derailleur...

105 5800 cassette uses a steel lockring instead of an aluminium one on the Ultegra cassette.

Number of gear teeth can be seen here. Coming down from 32T is 28T, 25T, 22T, 20T, 18T and so on.

Comes with a plastic holder which is useful if you know how to use it to slide the whole cassette onto the freehub body.

Only the largest three sprockets in the 105 cassette are mounted on the aluminium spider, the rest are individual sprockets.

Back of the aluminium spider. On the Dahon MuEX, I did a modification on the Ultegra cassette to fit the 11 speed cassette on the 10 speed freehub body, but it is not required here as an 11 speed freehub body is available.

Resin spacers are used instead of aluminium spacers. Material is PPS which is very compression-resistant. In fact, if you drop one on the floor, it sounds exactly like a metal part.

Weight of the 105 11-32T cassette is 305 grams. Just 25 grams heavier than the Ultegra version.

For a detailed comparison between 105 and Ultegra cassettes, check out this other post.

Next up will be the other components that will be installed on this bike, such as the brakes and the shifters.


  1. Hi Steve, I read your post with interest as I'm planning to build a 1x drivetrain flat bar road bike. I've been procrastinating a long time to do this and am in the process of gathering information and suitable parts. I could do something similar to your choice of parts, except for shifters and maybe I'll stick to 105 rear derailleur. Any thoughts on a 12 or 13-speed drivetrain or is this even available today?

  2. Will a 130 mm BCD Wolftooth also work with the 105 5800 crank?

    1. No, the 5800 crankset is 4 arm with 110mm BCD. You will need to get a matching chainring like what I use on the Dahon MuSP.

  3. Gotcha, I was looking at the 105 5700 on Aliexpress and that one has the 130 mm BCD.

    Regarding 11 speed shifter, is there a Shimano version to SRAMs GX11 trigger found on the Tern Verge X11? I'm hoping that since you last wrote this blog that there is now a Shimano alternative. Please advise.

    1. What shifter alternative are you referring to? Basically the shifter and rear derailleur must be compatible to each other, with the same brand. The road and mtb versions are also different.

    2. The Tern Verge X11 uses the SRAM X1 RD and Sram GX trigger. Also found by accident a Shimano SL-RS700 for flatbar. I'm guessing this is compatible with an Ultegra or 105 RD?

    3. Yes you are right. The SLRS700 flat handlebar shifter is compatible with 11 speed Shimano road RD.

  4. Aloha I would like to order tools as to remove the bottom bracket, chain ring, and chain protector. What do you use? Are the tools universal for folding bikes? Please advise.

    1. Chain ring will use either hexagon keys or Torx wrenches. Standard tools.

      There are a few differe t bottom bracket tools, depending on what type it is. Take note not to cross thread the bottom bracket threads to avoid damaging your frame.