I’m still running a triple and my front mech. has suddenly stopped shifting down from the big ring to the middle ring but shifts up, and down from the middle ring to the granny ring without issue.

I’ve replaced the cable and tried all sorts of adjustments and tweaking the mech. angle and playing with cable tension without success.

If I apply a small amount of pressure to the mech. at any point on the mech. the chain drops to the middle ring.

Any ideas? I’m beginner to wonder whether I have a bent cage.

Or a partially seized mech, do you have mudguards?

No mudguards.

I’m running a Singular Swift witch doesn’t have a front mech. cable stop but comes with a nasty shimmed, direct mount adapter; depending on how high I tighten the bolt everything seems to shift and move. The direct mount fitting itself doesn’t seem to great either and the front mech. shifts considerably depending on how tight the direct mount bolt is tightened – this combination is pretty troublesome!

That sounds like it’s prone to binding against itself tbh, is there no other front mech that will fit?

i use one of these mechs, where the cable goes out the front of the mech, https://flic.kr/p/KxifSj

it’s on a surly, which has cable routing for a dropper, so i just attached the mech cable to those.

Could be a bent cage or just that your DM adapter needs twisted around the frame by a degree or so.

Well the chain drops from the big ring in maybe 1 in 6-7 tries, otherwise the mech just rubs against the chain but no drop; the slightest inward pressure on the mech and the chain drops. Shifting up the rings or down from the middle to the granny is fine.

Gradual change or sudden? Presume it’s all adjusted/set up properly?

Seems sudden and was setup and working.

Just go 1x…

I’m new here, did I do it right?

And set up now all OK? Alignment etc? Csge not bent or widened?

I can’t guarantee that the cage isn’t bent or widened; currently looking for a 3×9 direct mount front mech. to buy.

Have you tried rotating it by a couple of degrees?

I’ve tried a variety of different angles without success I’m afraid. I’ll have another play tomorrow (off to work soon) but might try and find a new mech. to try.

Still the same; periodically the chain drops cleanly to the middle ring but about 70% of the time it just sits on the big ring grinding along the mech.

The only other variable is the EBB (I’ve not had one before); depending on its position the curvature of the mech. to the chainrings changes.

EBBs are for tensioning chains in single speed setups.

If you’re  moving it you’re essentially changing the chain length.

I see what people mean about edits not showing up immediately. I just invisibly corrected two autocorrect spelling errors immediately after posting.

Ah…EBB…my guess is the BB is sitting forward of where it “should” relative to the front mech.

The mech then is contacting the chain further back than designed to, and it’s not enough for the chain to drop.

So, having had experience with the rubbish plastic DM adapter On One used to supply, I’d say that the source of your troubles was that the mount moved and thus the cable tension on the mech was not constant. If you’ve since moved the cage and adjusted the EBB then really it’s time to go back to square one and fit and adjust a front mech from scratch after checking chain length isn’t now too long/short.  If you can replace the DM mech and adapter with a banded mech you will find life becomes far more reliable.

Ah…EBB…my guess is the BB is sitting forward of where it “should” relative to the front mech.

So does it need to be directly in line with the seattube?

I don’t know – but they can be really sensitive to set-up (eg the manual usually states the chainstay angles the mech will work with) and if you use a mech fdesigned for larger chainrings, the gap created can cause these issues.

This is the only thing that is obviously not within the likely parameters (and doesn’t explain the suddeness)

the cable tension on the mech was not constant

It would have only reduced, and that would not cause this problem.

I’m clueless to be honest. I’ve ordered a band-on cable stop and have an old XT band on mech. (the equivalent of the DM one I’m using) that always seemed to work, and I’ll try that; if that doesn’t work I guess that I’ll have to play with the EBB.

I suppose that the only other possibility might be the shifter (I bought them from someone on here years ago).

I really can’t afford a drivetrain upgrade at present.

I would try adjusting the EBB until it’s in line with teh seat tube. Cost: £0.

Moving the EBB inline with the seat tube hasn’t changed anything (although I think that I’ll leave it where it is now, as it’ll probably assist shifting) so it’s either the direct mount mech & adapter or shifter.

I’ve fitted a conventional mech. but the band-on cable stop I ordered on Wednesday still doesn’t appear to have been dispatched so I’m a bit stuck. Is there any way to bodge a conventional mech. to a frame without a cable stop (until mine appears); zip ties don’t seem to work?

Interesting. I don’t think there’s any way to bodge a cable stop.

My guess would be a bit of grit in the mech stopping it moving – I have had this happen

Had similar issues years ago when commuting all year round the front me hoch got gummed up with road grime.  took it off clean it deeply and lubed up and worked a treat. Something easy and free to try.