Rear derailleur shifting backlash

Question

I have a problem with my rear derailleur, which I cannot find a solution to.

The shifter has some kind of backlash, when I shift up it all goes perfect, same as if I go down. But when I try to turn the shifting direction, so for example I go up a gear then I try to go down a gear then it just doesn't shift. I need to go down twice to go to the next gear. If I go down again it works fine. I was suspicious of the limit screws but this happens mid-way too. So for example from gear 4 to 5. And it is repeatable, I can never just go up to 5 then go down to 4 with one click. And after the two clicks the next clicks work fine and take me gear by gear.

I have a 9-gear Shimano Deore XT derailleur, bike is relatively new, 6 months old.

Trying to find a possible explanation to this, hence a potential fix. Any help would be appreciated.

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Thanks a lot guys. I will try cleaning the wire and look for dirt around. I keep my bike inside and clean it regularly. I only touched the limit screws because I was worried something might have moved, generally I do not touch these. I'll post back once I have some time to fiddle with it. Thanks again.

Answer 1

Presuming this combination of shifter/cable/cassette/rear mech used to work fine together, then something has changed.

I'd start by lifting the bike, and make sure you can actuate the rear mech by pulling on some exposed inner wire while slowly hand-pedalling. You might need an assistant, a workstand, or some cord to suspend the bike a little.

The symptoms are consistent with some resistance in the outer cable housing - your hands are strong enough to force the inner cable through the outer when changing to a lower/easier gear, but when changing to a higher gear only the derailleur's spring is pulling on the wire.

Check the rear mech for general dirtiness - if it is caked up with dirt and oils then the pivots will resist movement. Clean it good-n-proper

If that doesn't help, check for rust on your inner cable, and any damage to the inner or outer. If found, replace both.

If you store your bike outside in the weather, then stop doing that.

The rear limit screws are generally not something you ever need to touch once they are set - the edges of the cassette do not change.

Answer 2

You should only need to adjust the limit screws if the derailleur can’t move to the highest or lowest position because it runs into the limit screws.

In your case the barrel adjuster for cable tension should be all you need. If you can’t get shifting up and down to work properly it’s usually because you have too much cable friction. This could be due to damage or simple wear of the cable and cable housing.