chain drops between front rings??

dieselgeezer
dieselgeezer Posts: 231
edited October 2010 in Workshop
Any thoughts as to why, when shifting from 50 to 34 ring, the chain sometimes, but not always, doesn't travel far enough over to actually engage the teeth of the 34. It seems to get stuck in "no man's land" between the 50 & the 34 meaning no forward motion. Have tried altering the front mech limit screws but to no avail. It's a 9 speed with Ritchey compact chainset.
Thanks in advance.
-- "I am but a spoke in the wheel of life" -- Ghandi

Comments

  • Monty Dog
    Monty Dog Posts: 20,614
    Sticky front mech cable or gunged up mech?
    Make mine an Italian, with Campagnolo on the side..
  • disconnect the cable from the deraillieur. the cage may swing further; see if the chain meshes then.
    Go for the break
    Create a chaingang
    Make sure you don't break your chain
  • Airwave
    Airwave Posts: 483
    I've had the same thing a few times.When changing from the 50 down to the 34 the whole thing comes to a shuderring halt.So much so that the chain has marked the stays as it's got jammed between the rings&pulled the rear mech up&tight.Checked the cable-ok.The mechs well cleaned&oiled.Seems to happen infrequently for no apparent reason.But really annoying when it does.
  • John.T
    John.T Posts: 3,698
    Airwave wrote:
    I've had the same thing a few times.When changing from the 50 down to the 34 the whole thing comes to a shuderring halt.So much so that the chain has marked the stays as it's got jammed between the rings&pulled the rear mech up&tight.Checked the cable-ok.The mechs well cleaned&oiled.Seems to happen infrequently for no apparent reason.But really annoying when it does.
    Chain suck. Not the same problem as the OP. Common on MTBs. Make sure the chain and rings are clean and lubricated. Also check the rings for wear.
  • Presumably the "fault" lies with the inner ring. I put a new CT2 ring on last winter so I reckon it's only done about 3000 miles. The chain is clean. I'll make sure the ring is as well. Thanks for the tip.
    -- "I am but a spoke in the wheel of life" -- Ghandi
  • Airwave
    Airwave Posts: 483
    Just checked the wear on the rings.They look fine.But the piece of the thin piece of metal bridgeing the front&back of the mech has cracked.But weather that is the cause or has caused the problem i don't know.Just going to order a new front mech.
  • John.T
    John.T Posts: 3,698
    Airwave wrote:
    Just checked the wear on the rings.They look fine.But the piece of the thin piece of metal bridgeing the front&back of the mech has cracked.But weather that is the cause or has caused the problem i don't know.Just going to order a new front mech.
    Probably a result of the chain suck.
  • John.T
    John.T Posts: 3,698
    Presumably the "fault" lies with the inner ring. I put a new CT2 ring on last winter so I reckon it's only done about 3000 miles. The chain is clean. I'll make sure the ring is as well. Thanks for the tip.
    Are both rings the same make and both marks lined up with the crank.
  • AndyI
    AndyI Posts: 156
    Have you checked the chain to ensure a 10sp chain (which is narrower than 9sp) hasn't been fitted by mistake? Once the chain is derailed by the mech it should fall into place on the small ring without sticking. the gap between the rings should not be wide enough to trap the chain. The Ritchey Compact with octalink b/b appears to be 9sp specific. Also, check the chainring bolts to ensure they are tight.
    A racing mind in a touring body.
  • AndyI
    AndyI Posts: 156
    Another thought: the Stronglight website shows the CT2 compact chainring for 10/11 speed only. I wonder if your replacement CT2 inner ring is compatible with a 9sp set up? Having said that I run a 105 triple 10sp chainset with a 9sp chain and cassette and it works perfectly. Still, tricky things bikes, and if it's not a 9sp specific chainring it could be exacerbating your problem.
    A racing mind in a touring body.
  • satanas
    satanas Posts: 1,303
    The whole "x speed specific" thing re cranksets is a furphy IMO. I've successfully used 7/8 speed cranksets with 9 and 10 speed chains a number of times. If the cause *is* chainsuck, then it's likely the outer ring that's the problem.

    However, if the chain is actually sitting between the rings (no "drive"), the problem is not chainsuck. As well as adjusting the limit screws (and checking that cable tension is low enough to allow the mech to move further in), you could try *carefully* bending the front edge of the outer cage plate in slightly. This should speed shifts up. Don't do this is your derailleur has a carbon outer plate! You may find that by the time you've got the chain to shift down satisfactorily, it goes too far and lands on the BB shell; in this case a Deda Dogfang (or similar device) is recommended.