Need some technical expertise

[SamIAm]

On one of my bikes, when changing from the big to small chain ring, the chain goes into limbo between the two rings. It doesn't wedge down in between the rings, just kind of floats to the side of the small ring.

It is a Compact Campy 10 set up, the chain is 10 speed and the limit screws are set appropriately.

It happens on 10% of such shifts, no issue going from small to big.

Has this ever happened to anybody else?

[AngryScientist]

i recommend taking a look on the stand. is the FD snapping down to the small ring quickly? meaning is the FD hanging up mid travel? if so, might be some cable friction/binding issue.

if not, how old is the big chainring? as they wear, the ramps and pins get less effective, if its super worn, that could be the problem too...

[eddief]

what happens if you turn the inside limit screw to allow the derailleur to bring the chain in some more? seems at some point the FD will spring enough toward the inside and the chain will have no choice about coming down to the small ring. if you can make it do this, then it would suggest you need to then back it off to the balance point just beyond what it is doing now. or maybe the angle of the dangle of the FD needs to be twisted some.

[chuckred]

That exact thing, but much more random. Probably 1 in a hundred or less. Of course never when in a stand. Never enough to really trouble shoot as it doesn't seem easily repeatable.

On one of my bikes, when changing from the big to small chain ring, the chain goes into limbo between the two rings. It doesn't wedge down in between the rings, just kind of floats to the side of the small ring.

It is a Compact Campy 10 set up, the chain is 10 speed and the limit screws are set appropriately.

It happens on 10% of such shifts, no issue going from small to big.

Has this ever happened to anybody else?

[rccardr]

Grit is most likely the culprit, probably in the spring area. Doesn't happen when you shift to the big ring because you're adding tension to the cable instead of relying on the spring to overcome any resistance.

Remove the FD and wash it out thoroughly in solvent or Simple Green, working the mechanism while it's immersed in fluid. Then re-lube all pivot points with Mobil 1 or Trilube, reinstall and adjust.

[Black Dog]

This can happen when you are on a small cog 12 or 13 and shift from the big ring to the small ring. The angle of the FD can have a big effect in this situation.

[UberBike]

How old is the setup ?
Check to see of the FD cage is still parallel, I've seen this happen a few times when the cage started to bow out from age.
Often going to a cheaper chain that might be slightly wider is an easy fix.
Cheaper model or KMC has been the trick for us.