Very strange this…bike was working fine yesterday but today the mech won’t move to largest or smallest cog. If I multi-shift to the smallest, it will drop in but there is no tension in the chain.

Cable appears to be sitting properly and all other gears are shifting flawlessly…

What needs done? I’m on holiday so have a rudimental toolkit with me – Allen keys and pliers.

B tension moved?

Don’t think so…got bike on a stand and now shifts to largest cog no bother, smallest will go but has no tension…

Will give the b tension screw an adjust.

I had something like this on an NX mech recently, drove me mad, I couldn’t figure it out at all. It was like the extension into the smallest cog just wasn’t there anymore even with the limit screw completely wound out. I ended up swapping it out for a brand new one I had spare and it worked fine (after trying new mech hanger first).

I haven’t tried to fix the old one yet but I assume its full of mud or something clogging it up so its not returning to its most outboard position for the small cog.

Good luck!

shift into smallest cog, fully tension the cable with the barrel adjuster, shift into second smallest cog with shifter and adjust (slacken) tension with barrel adjuster until it shifts cleanly into second-smallest cog, repeat to biggest cog.

Don’t think that will work, the mech appears to have no tension and then sits high resulting in the chain hitting the frame…however, I can’t work anything else out so I’ll release the cable and reset it and try indexing again, ta.