So I have a new bike, direct from manufacturer, had a little issue which was very swiftly/excellently resolved, but it meant that I didn’t ride it before the thing was sorted as I wanted to keep it clean before invisiframing it.

The thing that needed sorting meant I had to cut the gear cable, so I don’t know if it was set up and indexed all nice a smooth before I got my hands on it (I could have spun it in a stand but didn’t).

The thing is now for the life of me I cannot get the gears (Shimano SLX M7100 1×12) indexed, I’ve set up dozens of mechs from 8 to 12 speed inc converting my Trance to 1×12, never ever have I had so much trouble.

B tension is all set up and the cassette is in line with the line of the mech, checked a couple of youtube vids plus the Shimano manual.

If I have the indexing set up so I can get out of 12th gear into 11th it shifts ok, then into 10th is ok but catches a bit.

If I then try to change to 9th it goes straight to 8th. if I back off the cable a bit it’ll go into 9th, but then wont get out of 12th on one click. If I continue down the gears it’ll miss out gears and generally be shit, but it’ll sit in some gears ok, and which ones vary as I tweak the cable.

After 3 hours I cannot find a sweet spot where it’ll sit in all the gears and shift sweetly between them, its like the chain is too big (it’s not, it’s stamped M7100), I’ve even changed the cable.

Chainline looks ok, will sit in 1st no problem, in fact it will sit in 12 and 1st really well, just in between is awful.

Any ideas before I try to book it into a local shop for them to have a look (and wait another week or two to ride it)!?

Is the hanger bent?

Not obviously so, but I haven’t taken it off and had a close look, will do that now

Mech hanger tool.

Buy one.

Learn to use it.

Say goodbye to shitty gear changes.

Scotroutes, as I’m often trying to figure this kind of problem out… can you elaborate? Are they expensive tools? Easy to use? ta

@OP and stablebarns
(other manufacturers of course are available):

Have you routed the cable through the shifter correctly ?

Are you sure b-tension is correct? 12 speed is really finicky.

These big cassettes are fussier the 11-32 of old. Mech hanger alignment is a possibility. Worth getting the tool, then it is very easy to check and fix. Also the b tension is more critical. Conversely I’d say indexing is less critical so you can be a bit out and it’ll still shift. The negative side to this is that you can feel you have it aligned when you actually don’t.

Nice one scotroutes, that tool looks very useful… Also very straightforward. Nerve Wracking bending a non steel frame though? I mean how much strength does a carbon road frame have in that area where the mech is attached? Or does the hanger always give first? I guess that’s it’s job after all. To give out first, bend or break.

nickjb indexing is less critical than B tension? Or HAnger alignment less critcal? I couldn’t make out which order youwere prioritising?

Yeah I think a hanger alignment tool is going to be in order, hanger doesn’t look bent but still… thankfully brand new wheels or I’d be buying a wheel truing stand at the same time..

I think everything is as it should be, spent a while with magnifying glasses making sure that the cassette is aligned with the line on the mech (b tension), and have changed the cable and made sure it is installed correctly.

I even measured the distance between the sprockets on the cassette, all the same as far as I can tell.

So I think I have it narrowed down to either alignment or a dodgy shifter or dodgy mech, probably alignment.

FWIW I prefer the X Tools version to the Park one.

https://www.chainreactioncycles.com/lifeline-x-tools-pro-gear-hanger-alignment-tool/rp-prod122319

With the hanger tool, it takes very little pressure to move the hanger, you are not going to bend the frame. Read the instructions, obv you need to rotate the wheel with the tool to avoid any minor buckle in the rim from affecting the alignment. i.e line the tool up with the valve.

IIRC an old bolt up axle is the same thread as a mech mount – so screwing one one in instead of the mech gives you a rough and ready check of alignment. I have used this a couple of times

I had something like this. The hanger was pretty straight off the bike, but the interface with the carbon frame made it effectively not straight. So a quick tweek with an alignment tool put the hanger in alignment with the wheel. Shifting has been perfect ever since. Took me ages changing stuff until I eventual bought a tool. It’s amazing how out of alignment a lot of hangers really are.

I have the park tools one and use it a lot – prob a couple of times a year on each bike. It is surprising how easy it is to bend a hanger – 9 times out of ten if my shifting starts playing up, a quick tweak with the tool and it’s sorted!

obv you need to rotate the wheel with the tool to avoid any minor buckle in the rim from affecting the alignment. i.e line the tool up with the valve.

yeah, I was just sat daydreaming about riding my new bike on nice loamy trails and I realised this 🙂

tool ordered, we have 8 bikes (1 single speed so none of this shit) in the family so should get quite a bit of use, cheers

Missing spacer?

I can also recommend a hanger alignment tool. Have had one for many years and use it a lot.

One bike I had, the hanger kept going out of line. Had to use this 2 or 3 times per year to keep things running true. I’m sure the frame was actually misaligned on that bike from new!! Snapped a hanger once & 2 new hangers but never totally cured the skew!

I always use the alignment tool before starting any gear reindex on any bike. Saves so much time.

Only other thoughts for the OP: stupid one, but is the derailleur deffo 12sp and not 11sp? This might cause the sort of ‘nearly but not quite’ shifting.

Are the bearings/bushing in top jockey wheel ok? No play? Again, this would affect an accurate shift (esp on 12sp).

Is the wheel in straight?
Have you routed the cable correctly at the clamp bolt?
Is there anything interfering with the cable run, such as a down tube mounted mudguard?

” I had to cut the gear cable”

I’d be looking at this. Is the end of the outer crushed and pinching the inner?

mtnboarder +1

What else changed when you cut the cable? Did you remove the mech or cassette?
Was the bike out the box?
What bike?
Is the wheel in straight and correct?

I doubt this is the OPs issue but I spent ages faffing about with the indexing on one of my bikes the other day. Was just about to break out the alignment tool when I realised the derailleur bolt was half unscrewed – doh!

Wow, thanks for all the replies guys. I didn’t cut the outer, reused this, but replaced the cable, I removed the mech before dropping Frame and forks off with invisiframe, just because I could to avoid it getting knocked in transit.

Got work now, but going to take a look at the way the cable is attached to the mech later, have a nagging feeling…