[Closed] Chain jump... but only in SOME sprockets? Any ideas? 🤔

Mech. hanger straight.

By eye, or using a tool?

I spent ages trying to sort a similar issue.
Was a problem with the mech, buying a new one fixed it

Mech. hanger straight.

By eye, or using a tool?

My first thought too. I've had the same on some middle sprockets and was down to twisted mech hanger.

Eye v Tool...

By eye. Bizarrely, however, it was riding/shifting fine. I installed the new cassette/chain/cable. It now jumps in the middle sprockets, without me having ridden it (to damage the hanger)?!

So I'm fairly confident it's not bent / I wouldn't know how it got bent.

Nonetheless, a good shout to use the actual tool/gauge & go from there 👍🏻

Re: new mech. suggestion...

Assuming the hanger isn't bent, would this skipping/jumping be a typical symptom of a worn derailleur as opposed to a worn shifter? 🤔

TIA 👍🏻

I changed *almost* everything when I was getting skipping in one gear.

Chainring, chain, cassette, cable
Did the mech hanger with the proper tool

Took everything apart, put it all back together again. Re-indexed a few times.

I even changed the mech (an old Xt 10spd) for another old 10spd XT out of the spares box.

Spoke to the mechanic at the bike shop and he said it's almost always the mech.

Bought a brand new 10 speed Deore mech for ~£30 and it was immediately sorted.

Now have a spare cassette and chainring!

Spacer in the wrong place on the cassette or maybe the b link is bent, it can be aligned the same way as the mech hanger as you can unbolt the mech from it.

By eye.

Get the tool on it, they’re cheap enough if you don’t have one. IME since getting one 9/10 mystery gear errors seem to resolve with a check and straighten of the hanger.

Thought one. Mech hanger. 11 and 12 speed is sensitive. Needs a tool.

Thought two. Is the cable clamped on the correct side of the pinch bolt?

Had a similar problem recently, it was the cassette sockets gaps.

Something had caused two sprockets to bend in slightly, the application of a screwdriver to bend it back and a file for the fine tuning and its golden.

Thought two. Is the cable clamped on the correct side of the pinch bolt?

This.

Thought two. Is the cable clamped on the correct side of the pinch bolt?

Yep, this.
I had exactly these symptoms (albeit on a 12speed)
Cable was clamped wrong way round!

Generally speaking a variation in shifting quality along the cassette is a bent mech hanger.

Thanks for all the suggestions, folks - appreciate it.

Will get an alignment tool on it...

Re: cable on 'correct side' of pinch clamp, it's where it has always been - (looking at mech.) diagonally, 'top left to bottom right' (so to speak), towards the underside / through the 'groove'. Never thought about this tbh... what would be considered to be the incorrect way/location? Cheers.

Image of how to clamp cable on p14

Is the sleeve which the bolt to the hanger goes through, worn so the mech "floats" on it too much giving alignment issues?

Generally speaking a variation in shifting quality along the cassette is a bent mech hanger.

Echo's my thoughts. Even if it looks straight by eye. 12 speeds are really sensitive to it. I've replaced so many more mech hanger that's solved issues like this than I ever have done in the past with 9, 10, or even 11 speed.  I have a couple of spare hangers just for this

So, turns out the mid-cassette double-shift shifting issues are indeed as a result of a slightly bent hanger. Straight by eye. Slightly bent according to a tool / gauge. Lesson learned.

The tricky thing now... it's an integrated hanger on a steel frame 🙈🤔

Steel hangers on steel frames will take a lot of bending and re-straightening. It’ll be fine.

Glad you sorted it.

Now you have the tool, get it on every bike you own. I found most needed a slight tweak and even if I thought they were ok I saw the benefit.