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I have a few months old bike with SRAM Rival 1x. I have changed the cassette (to get closer gear spacing) and chain and can get the rear derailleur to shift almost perfectly swift and accurate both ways - apart from around the middle cog and onto the next one or two larger cogs. Here the shifting often can be, but not always is, hesitant or even not working, making the chain rub in-between cogs.

I have sized the chain by the standard procedure: Around largest cog and around the chainring bypassing the rear derailleur and then adding three inner and three outer links plus the powerlink, that is, a few links more than the four links recommmended by SRAM.

Since the bike is quite new and hasn't been out in mud or heavy rain, that is, the issue would not be lack of cleaning.

What could cause these problems with shifting at that particular point on the cassette?

  • Make sure your derailleur hanger is straight, the cable is properly routed through the derailleur, and that your cables are clean. – MaplePanda Oct 4 '20 at 18:24
  • Thanks, but those standard checks have been tried. What else could cause the issue only in specific regions of the cassette and only upwards (to larger cogs)? – agibsen Oct 4 '20 at 20:27
  • Big possibility: the new cassette is not compatible with the old derailleur. You might need a different model that swings inwards on a different path. How’s the current setup’s B gap? – MaplePanda Oct 4 '20 at 21:56
  • The cassette is an original SRAM PG1130, which should be completely compatible according to SRAM's charts. I had it work flawlessly with a similar cassette on a similar bike with Apex 1x. Also, if it was incompatible, it probably wouldn't exhibit near-perfect shifting? – agibsen Oct 5 '20 at 10:13
  • @agibson That’s weird. I don’t know what else to try then. – MaplePanda Oct 5 '20 at 16:27
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I have tried replacing the few months old cassette with a brand new identical cassette. While the shifting still isn't 100% perfect it has noticeably improved with no specific problem cogs anymore.

Update: I installed the original SRAM PG-1130 cassette (11-32) and a new PC-1130 chain (replacing a PC-1110 chain) sized around largest cog and the chainring bypassing the rear mech - plus three extra inner links and three extra outer links and the power lock link. Now the shifting was crisp and flawless across the entire cassette. However, I was missing the crucial, "sweat spot" 16T cog. So, with the same chain and length, I swapped the cassette back to the 11-28T (also PG-1130 series). And the shifting remains flawless! I think the main issue has been too short a chain all along - although I initially followed the official advice from SRAM with two extra inner links and two extra outer links for a 1x setup (They need to update those recommendations...)

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