Campag Centaur Rear mech/ chain problem!

richtw
richtw Posts: 118
edited November 2010 in Workshop
Help

I have been meddling with the rear jockey wheels on my mech to see how easy it would be to remove them. Cleaned them, refitted them and now have an annoying chain grinding noise that was not there before....

In short the mech shifts properly but when running an extreme chain angle (39 - 12) the chain is just catching the inside of the outer chain ring making a really annoying grating noise - it did not do this before and I know not to run angles like this but I would like to solve it.....

The limits of the mech are good, and the distance between the mech and the large sprocket are good.... I am lost? Could I have twisted the chain slightly - new chain?

Any ideas as to why it has started doing this and what can I do to resolve it?

Thanks

Comments

  • Ber Nard
    Ber Nard Posts: 827
    Jockey wheels are top and bottom specific - they have slightly different teeth profiles.

    I'd have a look to see if you've got them the wrong way round. They should be marked Upper and Lower.

    Rob
  • richtw
    richtw Posts: 118
    Just checked right way round and rotating in the right direction - confused...
  • Monty Dog
    Monty Dog Posts: 20,614
    With all modern bike transmissions, you'll get chainrub on the inside of the chainring when running from the small chainring to small sprocket - the easiest solution is simply not to put it in those gears - it's not good for the chain anyway.
    Make mine an Italian, with Campagnolo on the side..
  • richtw
    richtw Posts: 118
    Hmm I know but it is getting to me something chronic as it didn't do it before and it does now..... just can't figure out why?
  • EX DH
    EX DH Posts: 194
    probably just quieted down by all the shit that was on the jockey wheels.
  • Velonutter
    Velonutter Posts: 2,437
    Ber Nard wrote:
    Jockey wheels are top and bottom specific - they have slightly different teeth profiles.

    I'd have a look to see if you've got them the wrong way round. They should be marked Upper and Lower.

    Rob

    Hmm, didn't know that, how can you tell which one should go where as there are no instructions when you buy them.
  • Ber Nard
    Ber Nard Posts: 827
    I think it depends on the manufacturer as to whether they are top/bottom specific, certainly Campag are - it's marked on the side of the jockey wheel along with the direction of rotation.

    Don't know how much of a difference it would make to swap them round, though.

    Rob
  • double check you reall ydo have them rotating the corrct way around. It's easy to assume it is correct (one goes one way and the other the other way)

    Stupid question, but you do have the chain passing though the mech correctly and not over one of the metal tabs of the cage
    Recipe: shave legs sparingly, rub in embrocation and drizzle with freshly squeezed baby oil.
  • richtw
    richtw Posts: 118
    Thanks for the replies, yes the jocey wheels are in the right orientation, chain is routed correctly..... taking it into LBS as the mechanic is a rare genius and will get an opinion on Wednesday am!

    Still utterly baffled, now thinking chain may be slightly warped or twisted just enough to catch........
  • brucey72
    brucey72 Posts: 1,086
    Let us know the outcome. I had a similar problem, which just turned out to be a stiff link in the chain.
  • Velonutter
    Velonutter Posts: 2,437
    Ber Nard wrote:
    I think it depends on the manufacturer as to whether they are top/bottom specific, certainly Campag are - it's marked on the side of the jockey wheel along with the direction of rotation.

    Don't know how much of a difference it would make to swap them round, though.

    Rob

    Thanks Rob, I might have been lucky then as all of my bikes are Campag and when I clean and strip the rear mech I never check the jockeys so I will now.
  • richtw
    richtw Posts: 118
    Bent the hangar out by about 1mm, result being the grating noise! LBS straightened it back and all is good again......