Weird gear indexing issue

[ChrisS]

Well weird to me anyhow...

I'm on 1x11 with a SRAM 10-42 cassette and Shimano XT M8000 mech and shifter. It's shifting perfectly all the way up and down apart from one gear change. If I try and shift from 10 to 9 it just clicks away until I shift up another gear and then it jumps up to 8. Not had the issue until a couple of weeks ago, but I can't seem to fix it never mind what I do to the cable tension.

Anyone have any thoughts or things I could try?

[slarge]

Have you missed a spacer out of the cassette?

Same problem here, turns out I missed a spacer..... obvious if you look at it..........

[ChrisS]

Would have been a neat solution, but I'm pretty sure that's not the case. The cassette was installed by the LBS back in Feb along with some other work, but the problem has only started in the last few weeks.

[chrisjones]

Do you have a bit of something trapped in the cassette?

When you say 10 & 9 are we talking the big cogs? I find that the big (low) end of the cassette tends to be th most sensitive to mis-adjustment. I think it is because the step between the individual cog diameters tends to be bigger, so there is more of the adjacent cog for the chain to pick up on (if that makes sense?).

[ChrisS]

Do you have a bit of something trapped in the cassette?

When you say 10 & 9 are we talking the big cogs? I find that the big (low) end of the cassette tends to be th most sensitive to mis-adjustment. I think it is because the step between the individual cog diameters tends to be bigger, so there is more of the adjacent cog for the chain to pick up on (if that makes sense?).

No, the small cogs... Nothing trapped in the cassette.

[PaulE]

Don't know if it applies to SRAM, but if it's the biggest 2 cogs, have you tried winding the b-tension screw in a touch? They can rattle a bit loose over time and cause the top jockey to catch (at least on a Shimano mech they can)

[ChrisS]

Don't know if it applies to SRAM, but if it's the biggest 2 cogs, have you tried winding the b-tension screw in a touch? They can rattle a bit loose over time and cause the top jockey to catch (at least on a Shimano mech they can)

Sorry no it's the small cogs. I did try adjusting the b-tension screw anyhow to see if it made a difference, but I just messed with the low end then

[Cheeky Monkey]

Has the mech stop somehow been knocked out (I assumed going from smallest sprocket to second smallest)?

Bent the mech hanger?

Mech bolt come loose? (yep, I'm guessing wildly but they're the obvious things I'd check).

However, my other recent thread may indicate I am not best placed to advise on drivetrains and shifting

[ChrisS]

Has the mech stop somehow been knocked out (I assumed going from smallest sprocket to second smallest)?

Bent the mech hanger?

Mech bolt come loose? (yep, I'm guessing wildly but they're the obvious things I'd check).

However, my other recent thread may indicate I am not best placed to advise on drivetrains and shifting

It's the shift from the second smallest to the third smallest that's the issue. Mech hanger looks fine, but I do have a spare so could try swapping it anyhow and check bolts at the same time.

Not sure what you mean by the mech stop?

[ScotRoutes]

Always, always, always check mech hanger alignment before fannying about with indexing. I wouldn't even trust a new one.

There's a very good Lifeline X tools alignment tool for this. I much prefer it to the more expensive Park Tools version.

[Cheeky Monkey]

Has the mech stop somehow been knocked out (I assumed going from smallest sprocket to second smallest)?

Bent the mech hanger?

Mech bolt come loose? (yep, I'm guessing wildly but they're the obvious things I'd check).

However, my other recent thread may indicate I am not best placed to advise on drivetrains and shifting

It's the shift from the second smallest to the third smallest that's the issue. Mech hanger looks fine, but I do have a spare so could try swapping it anyhow and check bolts at the same time.

Not sure what you mean by the mech stop?

I meant the high and low limit screws, sorry, tech' language deserted me ;-)

[Laurensdad]

Always, always, always check mech hanger alignment before fannying about with indexing. I wouldn't even trust a new one.

There's a very good Lifeline X tools alignment tool for this. I much prefer it to the more expensive Park Tools version.

This.

[ChrisS]

Always, always, always check mech hanger alignment before fannying about with indexing. I wouldn't even trust a new one.

There's a very good Lifeline X tools alignment tool for this. I much prefer it to the more expensive Park Tools version.

Not done that... Will see if I can find a mate with an alignment tool. Thanks

[ChrisS]

I meant the high and low limit screws, sorry, tech' language deserted me ;-)

Ah no worries - I've set them.

[boxelder]

Worth also checking for a stiff chain link if it's the small sprockets.
I've got the same problem on two bikes between 2nd and 3rd gears......... Must be mid summer gremlins.