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Adjusting rear derailleur.

The problem occurs when moving up the cluster.

When cable tension is not enough the chain doesn't move from 7th to 6th cog (small ones).

When I increase cable tension (adjusting screw) the 7th to 6th is fine but from 3rd it jumps to 1st (instead from 3rd to 2nd).

From the other side, when loosing cable tension 3rd to 2nd is fine but 7th to 6th is not.

Any suggestions ?

photo of rear mech with chain on fourth cog

photograph of thumb shifter in position five

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I'm a little unclear as to your situation. If I read it correctly, the derailleur has trouble moving down the cluster, especially 7 to 6 and 3 to 2. What's confusing is you mention inadequate cable tension when there's a problem going from 7 to 6. When the shift is made going from larger cogs to smaller (lower to higher gears), the shifter is releasing a set amount of cable and overall cable tension is decreasing. The symptom of over shifting from 3 to 1 may be a result of not enough cable tension to prevent the derailleur from moving all the way to the start position under the small cog.

At any rate, be aware that the number one cause of shift problems is excess friction somewhere in the system. This could be caused by excess dirt or a physical flaw in the cabling. First thing to do is check that your rear wheel is fully into and centered in the rear dropouts. Examine your cabling including the ferrules (outer cabling caps) for wear or contamination. You could disconnect your internal cable from the rear derailleur, and while holding it with your fingers, manipulate the shifter through its range. Every shift should cause the inner cable to move smoothly without any areas of resistance. If you feel resistance, you could isolate where it's happening by moving you grasp up the cabling to the next area of exposed inner cable and shift again.

If it appears to be a cable issue, it's best to change the entire cabling, both inner and outer as well as ferrules. Damage or wear in one area infers that another spot may be close to worn as well, and, besides, you can't just change a section of inner cable.

Another thing to check is if the derailleur hanger is straight. This is a little complicated involving a specialty tool. However, a good estimation of the hanger straightness can be seen when looking at the hanger and derailleur from behind the bike. The hanger should be straight down and the derailleur cage parallel to the rear cogs. A bent hanger can often be replaced or using the hanger alignment tool to correctly align the hanger

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  • The problem is moving UP the cluster. When I add tension the move from 7th (smallest cog) to 6th (smallest after 7) is fine, but the move from 3th to 2th jumps to 1th. I got that probably the issue is cable and its housing.
    – Michael D
    Commented Sep 23 at 9:08
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    @MichaelD would you feel confident enough with tools to replace the housing and inner cable? That may be the quick fix, if there's too much friction in the line.
    – Criggie ♦
    Commented Sep 23 at 20:00
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    @Michael D Sorry. For so many years I've not used a shifter with an indicator. In my head, I simply had the cogs counting up from smallest...at any rate, my advice remains relevant. One thing you might also check is the B-gap. This is the distance between the upper jockey wheel of derailleur and the large (1st gear) cog. The chain should also be in the smallest front chain wheel. The distance (gap) should be 5-7mm. There is a screw on the derailleur (B-screw) that you turn to manipulate this gap. Clockwise increases the distance, CCW, reduces the distance.
    – Jeff
    Commented Sep 24 at 2:30
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    @Criggie, yes I am confident enough to replace the housing and inner cable. Usually, I've thought, that if the problem with cable or housing the shifting doesn't work at all.
    – Michael D
    Commented Sep 24 at 8:59
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Recently I had very similar symptoms as yours, I had a cable tension issue when I replaced my rear shifter with a new one and the derailleur was shifting from 8th to 7th when my shifter was in fact moving from number 7 to 6.

I resolve it by following this steps:

  1. If you have more than one front chain ring, shift chain to the biggest front chain ring, this is to align the chain with the smallest rear cog.

  2. Shift chain to the smallest rear cog and make sure shifter is on the highest number, in your case 7.

  3. Screw shift cable tension adjustment inwards, the one at the end of your cable housing on the derailleur, until it's nearly completely in.

  4. Unscrew the cable pinch bolt on rear derailleur, add tension (I use a pair of long nose pliers) and then lock the pinch bolt, make sure there's no cable slippage.

  5. Adjust your H (high) limiting screw so that the chain does not travel outwards pass the seventh cog, it must run smoothly without skipping noise.

  6. Move rear shifter to number 6 and if needed, add cable tension by unscrewing adjustment until the derailleur shift the chain over to 6th cog and runs smoothly.

  7. At this stage all other shifting from 5 to 2 should be easy, you may still need to tweak the cable tension adjustment a quarter of a turn at a time if needed.

  8. Move rear shifter to 1 and also shift the chain to the smallest front chain ring and then adjust the L (low) limiting screw so that the chain does not go over the biggest cog into your wheel spokes.

In my case I changed the old seven speed rear shifter to an eight speed one and testing the chain length was done before hand.

This resolve my problem, I hope it helps you too.

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    These steps are appropriate except that when setting the H limit screw, best practice is to do this without any cable tension (ie: when the inner cable is free from the pinch bolt). This assures that cable tension does not influence the setting, which is a state in which the derailleur spring is not stretched. It is the starting, baseline setting where the tips of the teeth upper jockey wheel of derailleur rests in line, under the outer plane of the smallest cog wheel. The chain should also be on the largest front chain wheel (the highest gear of the system).
    – Jeff
    Commented Sep 24 at 10:30
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    When setting the rear der's low, L-limit screw ( and the B-gap--distance between the tips of the teeth of the der's upper, jockey wheel and teeth of the large rear cog), the chain should be on the smallest front chain wheel and largest rear cog--lowest gearing setting. When you remove slack from the inner cable when fixing cable into the pinch bolt just AFTER setting the H-limit screw, it's important to remove the inner cable slack, but NOT so much as to cause movement of the upper jockey wheel out of its beginning setting under the outer plane of the small cog wheel.
    – Jeff
    Commented Sep 24 at 10:42
  • OK @Jeff then if I understand things correctly, when the chain is on the smallest rear cog, the amount of tension on the chain should not affect the amount of tension on the cable, thus the reason why the chain alignment takes precedence.
    – MindDBike
    Commented Sep 24 at 12:08
  • Hi @Jeff, I stand corrected and I edited my answer.
    – MindDBike
    Commented Sep 24 at 12:44
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    You are correct that cable tension doesn't correlate to chain tension so much (one could argue that a chain on the largest rear cog, a position where inner cable tension is maximum, is under more tension from the derailleur cage having its spring in extension at this position versus the other cog positions) however, it's best to think of cable tension in terms of what it's doing to the position of the upper, jockey wheel of the derailleur.
    – Jeff
    Commented Sep 24 at 23:01

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