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My old chain was skipping a lot, so I replaced it with a new one. The new chain barely skips at all, except for in the highest gears/smallest three cogs on the back cassette. The skipping comes progressively often as the gear increases.

The cassette does not look worn out. The rear derailleur seems to be indexed correctly but curls up very tight in highest gears.

I cut the new chain to be the same length as the old. In order to do this I only had to remove one link in the chain, which makes me wonder if the previous chain was cut too short (or too long).

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    Has it ever worked correctly with the old chain? Just to make sure your rear derailleur actually has enough capacity … – Michael Apr 15 at 18:16
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    Put the chain on the largest sprocket and post a picture of the smallest sprockets from as close up as possible. Without the chain on them obviously. – Carel Apr 15 at 19:36
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The cassette does not look worn out

A cassette that is worn does not look worn.

It'll skip anyway despite not looking worn.

I suspect your cassette is simply too worn.

(Interestingly, for chainrings the opposite is true: a chainring can look very visibly worn due to the non-even wearing at different crank orientations, and still work.)

The new chain barely skips at all, except for in the highest gears/smallest three cogs on the back cassette. The skipping comes progressively often as the gear increases.

This is exactly the symptoms of a worn out cassette. The skipping happens at the smallest sprockets. The smaller the sprocket is, the more likely it's to skip.

The skipping always happens when putting a new chain. With the old worn out chain, it won't skip unless it's practically destroyed as the cassette wear matches the chain wear. After a new chain is put in, the wears no longer match and thus the skipping starts.

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  • "The skipping happens at the smallest sprockets. The smaller the sprocket is, the more likely it's to skip." I think that’s only true if they are worn more. Which is often the case because there is simply less material on a smaller sprocket. – Michael Apr 15 at 18:14
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    @Michael it can also be true because fewer teeth are engaged – Chris H Apr 15 at 18:59
  • I was hoping this wasn't the case but it sounds likely. It became really bad after cycling in snow for a week and I gather the grit salt can erode the cassette quite badly. Before I get a new cassette is there any way I can know for sure that it needs changing? And are there any other likely causes for skipping? – Hello World Apr 18 at 14:08
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When you are on the largest chainring and largest sprocket the rear derailleur should look very extended. Some movement should still be possible. It should shift freely from second largest to largest sprocket and you should be able to e.g. push the chain to the chainstay.

On the small-small combination the derailleur shouldn’t be completely folded, i.e. there should still be some spring to it. There absolutely shouldn’t be any slack i.e. the chain visibly hanging down.

Generally the chain should be as short as possible to improve shifting performance and avoid chain bounce.

You don’t need much chain tension. If it skips even on the big chainring your cassette is probably worn too much.

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The skipping may come progressively often because you apply progressively more power (higher gears). I assume you are trying the smaller cogs at similar speeds.

Chain length may be an issue, but most likely the issue is the cassette. If your old chain skipped a lot, it is almost sure that it abraded a lot of of material from the cassette, especially when applying higher torque (---> smaller cogs on the rear are more worn out).

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