Chain suck ..........again

bazza333
bazza333 Posts: 86
edited June 2012 in MTB workshop & tech
Long story so I'll keep it short.
My Giant XTC1 has suffered from chain suck ever since I got it and even changing out the Raceface cranks for XT made no difference. In fact the only original parts left in the drive chain are the two mechs. I've never managed to solve this.
This weekend I decided enough was enough and with the bike in the stand I eventually managed to cause chain suck on demand and now realise whats happening!!!
When going from the middle to granny ring - just as the last piece of chain is about to drop off the middle - the outer side plate of the chain just catches one of the (lifting???) pins in the OUTER ring and gets carried up to the chainstay. It can be any of the pins.
I've checked there are two spacers in the driveside BB (Chainline is already over 52mm to the seat tube) so all I can think of doing is slightly spacing out the big ring????
Any thoughts would be appreciated.

Bazza

Comments

  • cooldad
    cooldad Posts: 32,599
    Have you got the right size chain?
    I don't do smileys.

    There is no secret ingredient - Kung Fu Panda

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  • bazza333
    bazza333 Posts: 86
    Depends what you mean by right size...it's certainly the right type and (without checking) I believe it has the correct number of links....it's something like an IG/HG90???
  • cooldad
    cooldad Posts: 32,599
    ps you don't have chain suck
    http://www.fagan.co.za/Bikes/Csuck/
    I don't do smileys.

    There is no secret ingredient - Kung Fu Panda

    London Calling on Facebook

    Parktools
  • bazza333
    bazza333 Posts: 86
    I think my chainstay would disagree with you but i can see where you are coming from.
  • nicklouse
    nicklouse Posts: 50,675
    bazza333 wrote:
    Long story so I'll keep it short.
    My Giant XTC1 has suffered from chain suck ever since I got it and even changing out the Raceface cranks for XT made no difference. In fact the only original parts left in the drive chain are the two mechs. I've never managed to solve this.
    This weekend I decided enough was enough and with the bike in the stand I eventually managed to cause chain suck on demand and now realise whats happening!!!
    When going from the middle to granny ring - just as the last piece of chain is about to drop off the middle - the outer side plate of the chain just catches one of the (lifting???) pins in the OUTER ring and gets carried up to the chainstay. It can be any of the pins.
    I've checked there are two spacers in the driveside BB (Chainline is already over 52mm to the seat tube) so all I can think of doing is slightly spacing out the big ring????
    Any thoughts would be appreciated.

    Bazza
    And what rear cog are you in when this happens?

    And it ain't chain suck.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • bazza333
    bazza333 Posts: 86
    One or two from the top. I'm not doing anything extreme like big to big.
  • nicklouse
    nicklouse Posts: 50,675
    bazza333 wrote:
    One or two from the top. I'm not doing anything extreme like big to big.

    so which are 1 or 2 from the top? what is top? the smallest cog number 9?
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • bazza333
    bazza333 Posts: 86
    No not 8 or 9 (small cogs) - when in 1 or 2 and going from middle to granny - basically when coming to the start of a climb. The chain side plates can catch on the big ring pins and get lifted up to the chain stay end result being chain jams ans another scar in the stay.
  • The Rookie
    The Rookie Posts: 27,812
    Is the chain the right length?

    Shift down in the big ring before shifting to the granny (ideally whouldn't be in granny in 9 or pref 8 anyway, poor shifting practice really) that way you move the chain at the rear towards the granny and reduce the risk of it catching the pins.
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.
  • YeehaaMcgee
    YeehaaMcgee Posts: 5,740
    He said NOT 8 or 9
    My photos
  • nicklouse
    nicklouse Posts: 50,675
    How worn is the middle ring?

    The chain should be no where near the big ring lifters in those gears!
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • The Rookie
    The Rookie Posts: 27,812
    YeehaaMcgee wrote:
    He said NOT 8 or 9
    Oops misread!

    Agree Nick, the chain shouldn't be anywhere near those pins....middle ring back to front?
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.
  • nicklouse
    nicklouse Posts: 50,675
    Just a thought.

    Have you ever had the chain rings off?
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • YeehaaMcgee
    YeehaaMcgee Posts: 5,740
    nicklouse wrote:
    Just a thought.

    Have you ever had the chain rings off?
    bazza333 wrote:
    chain suck ever since I got it and even changing out the Raceface cranks for XT made no difference. In fact the only original parts left in the drive chain are the two mechs.
    I'm guessing that's a yes, the chainrings have been off.
    My photos
  • bazza333
    bazza333 Posts: 86
    edited June 2012
    Correct - chain rings have been off (+3 different big rings - raceface/shimano/middleburn). That is a good theory and I will have a look in daylight but it has always had this type of problem ever since it was new....
    I believe the chain length is correct but again worth checking. I remember it certainly has a fair bit of tension.

    Wild guess on my part but..............could it be related to front mech travel??? IF the mech was adjusted to move the chain further off the middle ring when changing could that possibly mean it would be "hanging" on less teeth when it reaches the bottom?
    I only suggest that as a test run last night was perfect....but it was only a gentle ride round the roads and obviously I'm was being careful.
  • YeehaaMcgee
    YeehaaMcgee Posts: 5,740
    Ah, 3 different BIG rings? What about the mid ring? Has that been changed?
    My photos
  • bazza333
    bazza333 Posts: 86
    yes! Raceface to Shimano... :-)
    Basically the whole raceface setup got changed out when the BB went after less than 3 months. I lost patience and changed to XT.
  • nicklouse
    nicklouse Posts: 50,675
    So have they been fitted correctly? All aligned correctly? All the markers are aligned and in the correct place?
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • bazza333
    bazza333 Posts: 86
    The short answer is yes....as far as I know. However the bike has always had this problem no matter what kit has been fitted although I can't honestly say the chain catching on the pins has always been the issue as I only noticed that this week.
    I'll check the fitting etc over the weekend.
  • The Rookie
    The Rookie Posts: 27,812
    Can you take a photo of the chain catching the pins, to be clear this only happens during the shift from middle to lower ring? And the chain is catching the OUTER ring?

    Side on pic of the gears in 'big big' to show chain length would be a nice easy check.....
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.

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