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I have been having problems with cogs being skipped when shifting up or down.
Heavy pedaling will cause shifting sometimes.
To fix this I tried resting the high and low limit screw and reindexing the rear derailleur.
That did not fix the shifting problems so I replaced the shifter and adjusted the derailleur.
I still have the same shifting problems after getting a new shifter.

Is this an issue with the rear derailleur? It is about 8 years old and has been bang up plenty of times.

Is the hanger bent?

any thing else I should be checking?

rear derailleur hanger

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  • unrelated: is it rust on the hub and the spokes? or just dirty?
    – EarlGrey
    Commented Apr 29, 2021 at 5:28
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    Hanger is bent. Have you checked chain and sprockets for wear?
    – Noise
    Commented Apr 29, 2021 at 6:17
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    It’s basically never the shifter (unless its ratcheting mechanism is broken, which is pretty obvious). It’s either a bent hanger, bad rear derailleur adjustment, friction in the cables, chain wear or cassette wear.
    – Michael
    Commented Apr 29, 2021 at 7:14
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    @JoeK : The hanger looks OK but there is this odd 'S' curve in the pivot of the derailleur. And shouldn't the b-screw be visible from the rear?
    – Carel
    Commented Apr 29, 2021 at 10:25
  • @EarlGrey I have cleaned the cassette and chain. I haven't tried the hub.
    – pedalfaster
    Commented Apr 30, 2021 at 4:52

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The cage and it's pulley wheels look fairly straight up and down...so close that it shouldn't be an issue with shifting, although this is a game of millimeters and one can't absolutely rule out an alignment issue from a single photo. One thing I do notice is that the photo appears to show the upper, jockey wheel doesn't seem to be directly under the cog the chain is on. If this is true, than the system is not properly indexed. The guide pulley (jockey wheel) should run right beneath the the selected cassette cog. The barrel adjuster should be manipulated to get that in position (after appropriate shift tension is demonstrated by shifting successfully from 1 to 2 and 2 to 3). Specifically, here you would loosen (counter clockwise rotation) the barrell adjuster which tightens the inner cable causing the derailleur to move more inside where it will line up underneath the cog the chain is on. Obviously you'll want to make sure that the shifter is at the correct detente correlated to that gear. The limit screws will be set by now, but it's not unheard of to adjust the H or L screw by an ⅛ turn if there is trouble encountered when shifting to the extreme most cogs on each end of cassette.

You need also to evaluate the wear situation of chain and cogs. If the chain is worn (stretched) significantly, it will begin to ride over the teeth of the worn cog. This may be exacerbated by increased tension on the chain when peddling hard. Ghost shifting is also a symptom of wear and/or excess friction in the cable system (many causes). Look also to compatibility issues. The shifter and rear derailleur should be the same brand in most all situations: Shimano with Shimano, SRAM with SRAM. The cable actuation ratios of the 2 manufacturers' rear derailleurs are different and their shifters' cable pull differs because of this. As a result, mixing brands of shifters with the other guy's derailleur causes shifting to be very quirky. Any rear derailleur marketed as a 7, 8, or 9 speed will work with the 7 speed shifter (which I assume you are using) as long as they're the same brand.

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    “Specifically, here you would loosen (counter clockwise rotation) the barrell adjuster which tightens the inner cable” Or in other words: It looks like you need more cable tension. If that makes it refuse to shift to smaller cogs there is probably excessive cable friction.
    – Michael
    Commented Apr 29, 2021 at 14:34
  • @Michael Yes. I would agree that if tightening the inner cable is necessary to properly line up the pulley wheel to the cog and that leads to poor or slow shifting back down the cassette, there is likely something else going on and excess friction somewhere is one possibility. If alignment is good as far as derailleur hangar and cage and the high limit screw is set correctly so that the jockey wheel is lined up with the outside plane of the small cog, when the proper cable tension is obtained to make the shift up to the next couple of cogs, the jockey wheel alignment is going to be on as wel
    – Jeff
    Commented Apr 29, 2021 at 22:09
  • @Jeff both shifter and rear derailleur are Shimano. The replacement shifter is right speed/cog number. I replaced the housing and cable for the shifter, but i could have done it wrong. I think I had the chain and cassette replaced a couple years ago. I'll look up ways of evaluating the wear on the cods and chain. I was following Park Tool's video on rear derailleur adjustment. I could never get consistent shifting without skipping cogs with the bike in a repair stand or on the road.
    – pedalfaster
    Commented Apr 30, 2021 at 5:13
  • I'm sorry to hear that. It definitely distracts from the ride, and then where is the carefree pleasure in shifting with impunity up and down the cassette maintaining the RPM's? Perhaps the derailleur should be changed. Eight years of consistent riding infers there may be some wear. Less than ideal spring tension--the opposing force to cable tension--may play a big role in poor shifting. Revisit the cable routing. Park Tool has a vid. Outers need to be secured at cable stops. The ferrules fully in and set snug within the stops.
    – Jeff
    Commented Apr 30, 2021 at 6:33

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