Eleven speed road groupset, about 6000km on the chain. Shifting is crisp everywhere except the 11 and 12 tooth cogs, where it jumps forward under pressure. Fine when spinning lightly, skips when I stand up. New cable and outer fitted last month and the B tension looks right. Chain checker reads just under 0.75.
Replace the chain at 0.5 on 11 speed and you will usually get three or four chains out of one cassette. Waiting for 0.75 costs you a cassette every time, which is much worse value than the chain you were trying to save.
0.5 on 11 and 12 speed, 0.75 on 9 speed and below. Narrow chains have less material to lose.
Worth checking the jockey wheels while you are in there. Sloppy upper jockey adds noise and vague shifting, though it will not cause the skip you describe on its own.
Under power only is a wear symptom. Under all conditions is an adjustment symptom. Useful rule of thumb.
@lowtech_lior · 3mo ago · 3 replies
Chain and cassette, and your checker is already telling you so. Just under 0.75 on an 11 speed is well past the point where the small cogs are gone - they have the fewest teeth sharing the load, so they wear first and they are the first place a stretched chain skips.
The test is to fit a new chain only. If it skips worse in the small cogs immediately, the cassette is worn too. If it is silent, you caught it in time. At 6000km on 11 speed it is nearly always both.
Indexing is not your problem. Cable and B tension issues cause hesitation across the whole range, not load dependent skipping in two cogs.
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@lowtech_lior · 3mo ago
Check the hanger anyway while the wheel is out, it costs nothing to look. But a bent hanger does not care which cog you are in.
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@chain_wear_chase · 3mo ago
I was hoping it was the hanger. Fine, both then.
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