Slight indexing issues on new 11 speed drivetrain -- normal?

Question

I have a 20" folding bike that is about a month old and came with a Tiagra drivetrain. I subsequently switched it out to a 11 speed drivetrain (Shimano 105 R7000 with flatbar SL-RS700 shifter). The cassette is an ultegra 11-30t and the chain is a KMC X11EL. 56T single chainring in front. all are brand new.

I was having indexing issues in that when I tuned the tension just right for the smaller cogs, the bigger cogs would have its indexing slightly off such that it will chatter. I would then have to turn the barrel adjuster clockwise, but when I went down to the smaller cogs, I would then experience a bit of chain chatter.

Having Googled extensively I thought the issue would be either the cable or the hanger. So I changed the shift cable and housing and made it slightly longer than needed to avoid shifting issues due to kinks etc. Then I bought the park tools dag3 and aligned the hanger to about a 1mm-2mm tolerance (think it was off by about 4-5mm at the start).

Changing the cables and housing didn't change a thing, though aligning the hanger seemed to help somewhat. However, I am still experiencing the symptoms (in that when I index for the smaller cogs, I need to make the cable tension looser by about two or three clicks when I move to the larger cogs for it to be perfectly indexed) though I am able to find exactly one or two barrel adjuster positions that works reasonably well.

However, I notice that, when shifting from smallest to largest cogs, everything seems ok. But when shifting from the largest to second to third largest cogs, I get the same chatter noise and I need to turn the barrel adjuster about two clicks clockwise. But if I do so, I get a very slight chain chatter on the 2nd and 3rd smallest cogs. I tried changing shifter cables again to another Shimano but this did not help. The sound is very subtle but noticeable. I confirmed this by recording a slow motion video on my phone and the chain rubs against the smallest cog ever so slightly sometimes. Turning the barrel adjuster back anticlockwise works but then I end up with the same issue on the larger cogs.

Now the kicker is... I feel this only on the bike stand but when riding, I don't notice it at all. I brought it to a reputable LBS near my house and they mentioned that my drivetrain was perfectly smooth (though granted the shop is a little noisy so I was unable to reproduce the very slight chain chatter on the smaller cogs).

I also noticed on the park tools video on rear derailleur adjustment, the guy also needed to turn the barrel adjuster clockwise a little to get the larger cogs to stop chattering, but when he moved back to the smaller cogs, if you hear carefully there is actually a little bit of chain chattering against the next cog, though he claims in the video that it is indexed properly.

So... Could my expectations just be too high? I've already tried 2 different cassettes, shifters and RD, even put on a new hanger and realigned so I'm really not sure what else could be wrong (kmc cables being too thick, perhaps?). Also played with b tension which didn't really help much.

I'm wondering if it's normal for the upshifts to be very slightly different from the downshifts? And is it normal for indexing to be very slightly off in different cogs?

Answer 1

On my 11 speed Ultegra R8000 I initially had some noise and vibrations even though the chain was perfectly aligned. Apparently the cassette has some very aggressive teeth and narrowly spaced cogs which tend to catch the chain slightly if there is no load. It went away with time, probably because of wear.

If you can see that the chain is perfectly aligned with the sprocket while in a certain gear and it shifts nicely (under load) I’d ignore the noise.

Answer 2

I'd say in this case the best you can do are to:

• Ensure that you are using the official Shimano stainless cables and housings (SIS-SP41). My experience with cheap knock-off housings has been that indexing with them is off. You might think the housing is a non-important component that can be bought from any manufacturer, but actually this would be wrong. The housing is very important for proper indexing operation.
• If the housings and/or cables are old, you might as well change them anyway (but in your case they apparently aren't old)
• Ensure you use end caps on the housing, and that those end caps are of the proper type (Shimano plastic). There are different types of end caps: some have O-rings and some don't. The segment of housing near the rear derailleur should use O-ring end caps, with the others it's your choice (MTB riders may want O-rings everywhere for minimal dirt intrusion and road riders may want O-rings only on the rear derailleur housing segment for minimal friction when new). Some shifters and/or rear derailleurs might use a non-standard end cap type, to make sure check the official Shimano documentation.
• Ensure every housing segment if of perfect length. See The Four Commandments of Cable Routing. So you by making the housing segments bit too long might have actually violated the commandments. However, on folding bikes you have to not only consider the optimal of length when unfolded, but also the consideration that the bike can be folded without housing segments limiting folding in any manner.
• Ensure you cut the housings using the proper tool (a wire/cable cutter, not a diagonal cutter) resulting in a good cut. For perfectness, you could bend the housing into the form it's on the bike, and do the cut while the housing is bent in its final form. This means the small wires on the housing are all cut to perfect length in bent form (but if you make it straight you'll see they are not perfect in the straight form, which is fine since the housing is not straight when mounted to the bike)
• If you don't have whole-length housing (so that there are exposed inner cable runs), after the housings have been installed to the bike, do what is called by Shimano "removing the initial cable slack". You operate the shifter and rotate the drivetrain to move the rear derailleur to its fully actuated position (big sprocket). Then you pull on some run of exposed inner cable hard. The derailleur is already fully actuated so it can't move anymore (it'll hit the low limit screw). If you use a lever shifter such as thumb shifter, downtube shifter or bar-end shifter you can pull very hard on the exposed inner cable (but you must resist the movement of the shifter by using your other hand), if you use a trigger shifter such as STI or Rapidfire shifter then you should ideally somewhat limit the force you use to pull the inner cable so the shifter won't break. The purpose of this is that pulling hard on the inner cable seats all housing ends and end caps.

Even if you follow all of the above mentioned best practices, my experience is that the indexing will always be a bit off. If it's so much off that you have to push the derailleur far away from the sprockets using the B tension screw then something's wrong in your setup. You should be able to shift gears after moving the derailleur very close to the sprockets using the B tension screw.

In Shimano systems, the rear derailleur upper pulley anyway has a bit of float on it. This is there to allow running well even if there's minor inaccuracy in the indexing. The indexing should be so accurate that the floating upper pulley eliminates all nasty sounds from minor inaccuracies.

Also you should adjust the indexing only on one gear. Which gear to use depends on the mismatch direction. Take a hard look at whether the rear derailleur moves too little or too much per shift. If it moves too little per shift, then adjust the rear derailleur on the second smallest sprocket so that you make the chain rub slightly against the third smallest sprocket and then rotate the barrel adjuster in the other direction to just eliminate the rub. If it moves too much per shift, then adjust the rear derailleur on the second biggest sprocket so that you make the chain rub slightly on the biggest sprocket and then rotate the barrel adjuster in the other direction to just eliminate the rub.

Answer 3

It sounds like your folding bike has short chainstays, which result in marginal chain angle at both extremes of the cassette. This issue is common on bikes with very short chainstays, such as folding bikes or kid's bikes.

I don't know about for the latest 11-speed drivetrains, but Shimano traditionally warned against running their road components on bikes with chainstays less than 405mm. A a 20-inch kid's bike or folding bike may have chainstays of 350mm or less. Possible solutions for short-chainstay bikes include using an internal-gear hub, or a more forgiving drivetrain (such as 8spd) which may be more tolerant of the chain angle. There are also drivetrains marketed for short-chainstay bikes, such as the Microshift Acolyte (also 8-speed). If you stick with your 11-speed, you may just need to live with a little bit of noise in the highest or lowest gears.