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Several months ago I replaced all gearing parts and switched from an 8 speed to a 10 speed system. All parts were brand new.

After replacing I noticed the chain slipping occasionally. Though I drive for months now, the phenomenon first happened days after replacing all parts.

I had the derailleur cable tightened after several weeks and once more after several months (it was tight enough this time).

It happens

  • on the cassette (whatever it is)
  • without heavy load (not accelerating from stand, riding uphill, putting only slight pressure to drive slow)
  • with moderate and heavy force too
  • without bumpy road
  • not during shifting the gears
  • with front gear 2 and rear gear 3 - 8, front gear 3 and rear gear 8 - 10 (I rarely drive lower gears, can't say whether it happens or not)
  • at most once within 50 km
  • with the same rate after more than 1000 km
  • with the rear derailleur Dyna-Sys switch on and off

I can't

  • reproduce it (at will)
  • say whether it happens in all gear combinations or not
  • say what exactly happens (chain trying to change the gear or messing things up somehow on the gear) since I can't see it

I had two thoughts:

  • the joined link could be a little bit stiff (but I can't see any stiffness when spinning the chain in stand)
  • the derailleur is not properly justified (I had it realigned after several weeks and months, though must admit, I'm not a professional in doing this)

The chain is properly and regularly lubed.

Should I still assume a stiff link or the derailleur being misaligned? What could be another reason?

And no, this was not a mixed setup. I read this question on a new bike too, I already addressed the mentioned issue, I think.

Setup:

  • FC-T521 3 speed crankset
  • XT 10 speed cassette CS-M771-10
  • XT FD-T780-6 66-69° 3/10 speed front derailleur
  • CN-HG95 10 speed chain
  • Shadow Plus RD-M786 10 speed rear derailleur
  • I personally find that tuning the derailleur is a tough trick to get right. Perhaps try bringing your bike to a professional and ask if he can see a problem with it. If he sees the problem fast enough he might not even charge you for it (don't count on it though ;)) – Bono Jul 23 '17 at 7:47
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    This is a difficult one to diagnose without a bike in front of me, but there are , as you noted, 3 options here. A stiff link is a likely culprit. I note that you were unable to find it is the stand, if so. Try checking the chain by pedaling it backwards on the stand, slowly, and watching for the derailleur cage to "jump" slightly as the chain passes through. Second, a poorly adjusted derailleur can cause the chain to try to move to the next higher or lower gear. 3rd, you derailleur hanger may be bent. Solution to the last two is the same. Align the derailleur hanger, and set it up again. – zenbike Sep 12 '17 at 3:23
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Make sure the outer gear cables are cut properly (after removing the outer cable end caps), also make sure these end caps are not bent and are properly fitted. Check if there are any bends in your inner gear cable (if there is a bend in your inner gear cable this could prevent the cable from moving through the housing properly).

  • I accepted your answer as it matched my case best. When replacing the outer cables I did not cut them using a proper cable cutter. Thus the ends where crimped. This might have caused too strong friction. Though I'm not 100% sure if that replacement cured or at least reduced the slippage, the bad cable cutting was definitively an issue. – try-catch-finally Dec 19 '17 at 23:06
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a theory: you might have too much friction between the derailleur cable and its housing. such friction could prevent the chain from going to the intended place when you shift; when the friction subsides, the cable would move and the chain would slip into place.

apply some lube to the cable and slide the housing back and forth to spread the lube along. this could help if my theory is correct.

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    If he had new brake parts, they might have replaced his cables or cable outers with teflon lined ones. In that situation, it's best not to lubricate. – RoboKaren Jul 22 '17 at 23:20

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