Bit confused by this – there’s no noise or skipping in any gear, shifting to a bigger sprocket is fine, but shifting to a smaller sprocket doesn’t happen with one click.

I have to shift twice then back once to get to a smaller sprocket.

Chain and rear mech are clean, and I’ve just replaced cables and housings to try and fix this BUT IT STILL HAPPENS. 😥

If I back off the cable tension then I have problems shifting to bigger sprockets.

According to a chain checker, the chain just needs replacing, but googling suggests that a worn chain will skip rather than produce shifting problems in one direction.

I guess I’ll change the chain soon anyway, but does anyone have any ideas what could be wrong? Bent rear hanger?

This is 2×10, deore shifter and shadow+ rear mech (but it still happens with the clutch on or off), SRAM cassette and KMC chain.

Slacken the gear cable off a bit?

If I back off the cable tension then I have problems shifting to bigger sprockets.

Something is sticking in the cables (a badly cut cable outer maybe? or a cable end cap that’s not greased?) or the mech’s pivots are tight/bent/etc so it doesn’t move freely.

You can almost always shift to larger sprockets because you’re forcing that via the cable and you’re strong enough to do that. Shifting to smaller sprockets relies on the spring in the mech and if there’s drag it may not be able to overcome that so it doesn’t move far enough.

A bent hanger can cause this but will usually cause problems both ways (or at least it will if you adjust the cable tension)

Check the mech hanger for straightness

I had something similar to this and fitting a new chain sorted it. Surely worth a go for a few quid?

nemesis – Member

Something is sticking in the cables (a badly cut cable outer maybe? or a cable end cap that’s not greased?) or the mech’s pivots are tight/bent/etc so it doesn’t move freely.

You can almost always shift to larger sprockets because you’re forcing that via the cable and you’re strong enough to do that. Shifting to smaller sprockets relies on the spring in the mech and if there’s drag it may not be able to overcome that so it doesn’t move far enough.

I’d start with this. You are dragging the cable onto a bigger sprocket with the cable, but relying on a spring to pull it back down.
Likely that something is sticking in the cable run.

Don’t connect the cable, pedal with one hand while pushing the rear mech across to the biggest sprocket with the other hand. Then keep turning the pedals and let the mech come back down the sprockets a bit at a time, by moving your hand out of the way slowly. If the mech pulls the chain all the way to the smallest sprocket without issue, then the chances are it’s a sticky cable issue.

I’ve just replaced cables and housings

Are you cutting the cable housing too short (bends quickly at barrel adjuster)? If so, it will kink/bind causing friction and drag.

Sticky cable/mech or the b screw (think that’s the name). Too much and the top jockey sits too far from the cassette. I set mine up so the jockey ‘hovers’ just off the gear and check it through the range.

Should have mentioned that it’s full-length housing without any tight bends.

I’ll check the mech movement, the b-screw, the cable run (again) and change the chain anyway. I’ll have a squint at the mech hanger too. In fact I might try putting a spare hanger on and see if that changes anything.

Thanks all

Bump : It was the chain. I finally put a new one on without changing cables, rear mech adjustment or rear hanger and it changes up and down flawlessly.

I didn’t realise that 10-speed could be quite so delicate, I’m sure I wore 9-speed chains well past the recommended change without getting problems.