Chain coming off

Michael1965
Michael1965 Posts: 12
edited May 2017 in MTB workshop & tech
Hi guys, I've recently converted my mtb to a single front cog and 9 rears, I'm having a bit of an issue with the chain coming off the front when I'm in first gear, the problem seems to be being caused by the alignment of the front cog , if I eye it from the back to the front it's way out !! Is there anyway I can move the bottom bracket over towards the frame or even the cog? I need about 5mm, any help much appreciated

Comments

  • poah
    poah Posts: 3,369
    does it come off as soon as you change in to 1st gear or is it coming off when riding?

    did you come from a triple or double chainset? if its the triple is it on the middle position? assuming you are running a HT2 BB or similar you can adjust the chainline by moving spacers assuming you have enough clearance between the ring and the stay.
    CCDB IL coil CS first impressions

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  • The Rookie
    The Rookie Posts: 27,812
    Are you using a narrow wide chainring, a plain single speed or a ramped and pinned one for shifting one?
    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.
  • Michael1965
    Michael1965 Posts: 12
    Hi there, it comes of while I'm riding it, it was a triple set before and yes I'm using the middle one, I don't recall seeing any spacers on it ??? I also don't understand what the stay is?
    I don't know what a narrow wide chain ring is or anything about the pin, I don't think I'm as professional as some on here, the bottom bracket is the square taper type if that's any help,
  • larkim
    larkim Posts: 2,485
    When you've converted to a single cog, have you just removed the big cog and small cog and left the middle one in place, with the derailleur mechanism removed too?

    If so, your chainline *should* be in about the right place (it wouldn't make sense for your middle ring to be badly aligned before, though I suppose that can't be ruled out).

    In that situation the chain can find it difficult to stay on as the old cog that you're using is designed to allow the chain to move off it onto the bigger or smaller cogs with ease. What you might find you need is a narrow/wide chainring instead which is designed to hold onto the chain much more tightly (as it never needs to move).

    They can be picked up cheaply for about 20 quid from places like planet X.
    2015 Canyon Nerve AL 6.0 (son #1's)
    2011 Specialized Hardrock Sport Disc (son #4s)
    2013 Decathlon Triban 3 (red) (mine)
    2019 Hoy Bonaly 26" Disc (son #2s)
    2018 Voodoo Bizango (mine)
    2018 Voodoo Maji (wife's)
  • poah
    poah Posts: 3,369
    is it coming off on smooth or rough ground?
    CCDB IL coil CS first impressions

    MTB Scotland youtube channel
  • Michael1965
    Michael1965 Posts: 12
    It comes off on any ground condition, I've got a funny feeling I kept the big chain ring! Hence its so off set, maybe I should either go for a narrow wide chain ring?
  • JGTR
    JGTR Posts: 1,404
    If you are using your original middle ring then that's your problem, it's not designed to be used as a single ring, it need the front derailleur to stop the chain falling off.

    Fit a narrow wide chain ring, specifically designed to be used on its own as a single front ring.

    Also measure your chain line and work out if you need spacers, some rings come with spacers, everything you need is on google.

    Or just refit your front derailleur and use it as a chain device.
  • larkim
    larkim Posts: 2,485
    Michael1965 wrote:
    It comes off on any ground condition, I've got a funny feeling I kept the big chain ring! Hence its so off set, maybe I should either go for a narrow wide chain ring?
    Wow you must really like being in pain heading uphill!

    You've definitely gone down a non standard approach there, the usual plan is to have a front ring which has between 30 and 34 teeth up front. What were you hoping to achieve by going with just one ring up front?
    2015 Canyon Nerve AL 6.0 (son #1's)
    2011 Specialized Hardrock Sport Disc (son #4s)
    2013 Decathlon Triban 3 (red) (mine)
    2019 Hoy Bonaly 26" Disc (son #2s)
    2018 Voodoo Bizango (mine)
    2018 Voodoo Maji (wife's)
  • The Rookie
    The Rookie Posts: 27,812
    Depends on the usage, I have a 1x9 running a 44t NW and a 12:28 cassette.
    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.
  • Michael1965
    Michael1965 Posts: 12
    Thankyou everyone for your help with this, I don't struggle to much up hills, although there are not many in Norfolk!!! With reference to the 44 teeth front and the 12/28 cassette does that set up work ok?
  • The Rookie
    The Rookie Posts: 27,812
    That works fine for me on my commuter bike, yes, was running a 46T but that was just a bit too much.

    Its on a road crankset though, you'll probably struggle to get much over a 38 or 40T for an MTB crankset as a single ring.
    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.
  • Michael1965
    Michael1965 Posts: 12
    Hi guys just a brief update, I changed the bottom bracket for a 10mm shorter one and it seems to have stopped the chain coming off, the chain ring us running very close to the frame though around 2mm but it's not touching, I've also changed the cassette to a 11-34 to help my up hills when I do my sponsored rides this year, rode it yesterday and so far the chain has stayed on, I need to go wash the bike now!! Thanks guys

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