I have been using KMC X10.93 chains for the past 6 years. I replace the chain on a yearly basis (I ride about 3.5 - 4.5 k miles per year). This year after my annual major cleaning and maintenance cycle everything seemed fine for the first couple of weeks. Then I noticed a strange sound and feel every now and then from the drive chain. It's hard to describe, so instead I will tell you what i did.

1. replaced the big chain ring - no affect
2. Had bottom bracket looked at - it was fine.
3. Swapped my rear wheel with my wife's rear wheel - seemed to solve the problem but only rode with it for about a week - 100 miles.
4. replaced the cassette - first time I only used the spacer that came with the wheel 1.8mm (11s hub - 10 speed drive chain) - problem was probably worse
5. added the spacer that came with the cassette (105 11t-28t) to the one that came with the wheel - better than 3 but not really better than when I started (step 0)

One thing I did come to notice was that the "sound" definitely was chain related and switching the rear gear + or - one cog and back did seem to help once the noise stated - this is what lead me to replacing the chainring and cassette.

BTW, the bike and hence the original chainring and cassette had about 24000 miles on them so $70 worth of parts are not really wasted even if they were still "OK"

The other thing that I noticed when I changed the chain was that it looked a little different that what I had been getting all along.

Here is a picture of the links cut from one of my older chains and the latest one I installed not too long ago - both are KMC X10.93 chains.


Notice how the design of the bottom chain (newest) is very different than the design of the top chain (cut links from an older chain) particularly the upper left edge and lower right edge of each link (not to mention the black inner links vs the gray inner links)

Since the problem seemed to go away when I swapped wheels and got worse when I installed a new cassette without the proper spacer, and it seems to be affected by switching gears back and forth, I am beginning to think the noise might just be related to "bad" tuning of the rear derailleur and this new chain design is either more sensitive to it or at least makes a lot more noise when the alignment is off.

Can anyone speculate on what the reasons might be for this design change are, and what the implications might be? Anything else I can try to figure out what might be the cause of this somewhat random noise I hear.

Quick summary - Replaced chain - occasional weird chain related noise, replaced chainring and cassette - no affect, suspect new chain design (shown above) to be a factor.

First of all, clearly explained and good photo visual that easily shows difference.
Haven't a clue, first guess was purely a weight saving thing, but the cutouts have distinctly different shapes top vs bottom.

Are you sure chain direction is right, obvious question I know...

Only recently have a first 10sp bike in the family now, and I've used kmc 8 and 9 speed chains, so am interested to hear the answer to this.
Official answer from kmc may be worth the time of an inquiry to them.

I recall responding to an earlier post with a similar question and the chain manufacturer had indicated in ad copy that they were shifting aids.

As the clearances have gotten narrower and narrower the fudge window (of how all meshes with each other) has also gotten less. Not mentioned was when the wheel (with it's own cassette) or the original cassette were changed is if the read der cable "index" tension was also reset. If not then the very slight difference of cog location WRT the der's indexing position might not have been well coordinated.

As to the chain plate's differing scalloping I strongly doubt they are a factor for your issue. The plate's contours are more about the shifting smoothness and responsiveness then effecting after shift chain rub.

other things to check out are the cable condition, the guide pulley's wear and that cure all (by many people's claim) a bent der hanger. Andy

I can't say with certainty but I recall a couple years ago searching for the best price on one of these that they may have made a slight change in the design at some point and the packaging and designation changed a little as well and if anything would improve your shifting. Your old chain may be the older design and were still being sold as a not-so-old NOS. Notice there are different markings on the chains in your photos. Anyways just something to look into and I would contact KMC to confirm this. Also have you tried making any adjustments to the derailleur cable, might just need a little tweak.

Did you tighten down the cassette retaining ring good and tight? I was getting a noise in a couple of my middle cogs and could not figure it out for the longest time. Finally went over everything and found the retaining ring was not torqued down. Noise went away immediately.

Ive experienced this with both bikes with too loose and even too tight cassette tightening.

Did you measure the widths of the 2 chains? The deeper relief on the new chain may be needed because the plates are a little wider. That would make the chain easier to join and more reliable, but also more likely to rub on adjacent cogs.

em

I looked at an X10 that came on a bike I bought last year and it looks like your old one.
I'm not sure exactly what that means...

BTW, I should have replied to this some time back, but eventually I did figure out that the issue I had was due to the bearings in the freehub being worn out. I painstakingly replaced the bearings, only to have 2 spoke break with in a month, so I ended up replacing the wheelset.

Stuff'll happen when you put your bike to use for a while.