Single speed conversion....Chain fell off- Mtbr.com
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  1. #1
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    Single speed conversion....Chain fell off

    I converted my 1x9 to single speed, and used the same chain, and the 16t gear in the back. Under full sprint, hard pedaling, the chain came off.

    3 broken ribs, mild concussion, broken helmet, damaged ego, and many road rash cuts and bruises. ( This was Wednesday)

    Why would this happen? Chain alignment looked perfect. I also tightened the chain for no slack.

    Any insight for the SS conversion pros?

  2. #2
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    OUCH!!! That really sucks, sorry to hear that. Well looks like you had everything in order, the only thing I could think of is maybe you were running a ramped chain ring?
    The unexamined life is not worth living - Socrates
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  3. #3
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    Bike was stock with 1x9. Specialized P2. Still buzzing on vicoden and vodka but maybe I am too strong and flexed the cranks/lower part of the frame to a point that the chain was no longer aligned? I don't know.
    Anyone want a P2 for cheap? lol.

  4. #4
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    Sad to hear you hurt yourself that bad.

    Did you use the 16t cog from the cassette?
    Ride more!

  5. #5
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    Could be the alignment wasn't perfect. I had the same thing happen (minus the injuries - I mean the derailment) recently and shifting the cog one spacer over corrected it. I couldn't see the slightly misaligned chain.

    Hope you heal up quick!

  6. #6
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    No. I used the 16t from the conversion kit I bought.


    Quote Originally Posted by asphaltdude
    Sad to hear you hurt yourself that bad.

    Did you use the 16t cog from the cassette?

  7. #7
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    Quote Originally Posted by makomyday
    No. I used the 16t from the conversion kit I bought.
    What conversion kit did you buy?

  8. #8
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    I would second the guess that your front chainring was ramped (to make it easier for the front derailleur to move the chain from one ring to another under load...) Perhaps some combination of rider strength, frame flex, lateral loading on the chain from the bike having any side movement, etc... made the chain leap off. Sucks you got hurt so badly (always a good idea to "ease" into full power applications with any new or changed drivetrain components next time!). A couple of reasons to use 1/8" chain and ring/cog when you go SS: Larger tooth and bushing width on the chain and rings makes for longer wear, and 1/8" (BMX-style) chains are not designed to have as much lateral flex as derailleur chains, so it is harder for them to get out of line and try to climb off the ring or cog. When I set my bike up as a 1 x 9 I have to use either a front derailleur locked into place, or a chain keeper to prevent my chain from coming off on the inside over bumpy terrain in almost all the gears. Hope you heal fast and don't give up on the bike - but new ring and chain may be a good idea!
    R.I.P. Corky 10/97-4/09
    Disclaimer: I sell and repair bikes for a living


  9. #9
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    If the bike came stock as a 1x9, it probably doesnt have a ramped chainring.
    It could be anything, chain line, alignment of your tensioner, too much slack in your chain and it bounced off, 9 speed chain not fitting properly on your cog (they are thinner than a 3/32" chain, so not ideal for SS use).
    Hope you heal up soon, and jager goes much better with narcotics.
    Sue specialized. Since they're always suing everyone else, it would be nice if someone returned the favor. I realize it probably wasnt their fault, but that just makes it more suiting.

  10. #10
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    I would concur with ISAR you are using a 9 speed chain on a SS cog which is going to be wider than the chain was designed for so it may not have been seated properly, also how worn was your old chain? If it was very warn then it could have skipped on the rear cog.

    Healing vibes on the injurys' though dude, don't give up on SS though, chains bust on geared bikes as well (maybe more often with all the side loads pulling the plates apart)

  11. #11
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    I missed that little detail about it being 1x9 to begin with - but on the issue of SS conversion with the cog being wider - I have seen a number of kits that came with 3/32" cogs, as they would expect that someone may be converting over a formerly-derailleur equipped bike. That said, it COULD be a 1/8" cog and that would not let the chain drop into the trough of the tooth profile and cause problems (even split the chain side plates in some cases...) Also, even though it is not likely ramped, the 3/32" front ring, if you end up going with a 1/8" chain might let the chain slop around and cause problems. Homebrewed Components makes nice, very reasonably priced cogs and rings. Check what you have and if you need something, get his ring/cog and a KMC 1/8" chain and you should be set. And if you sue the Big S you will have tons of money to buy multiple rings and cogs and maybe even a Ti SS frameset. (Make sure you buy a seatbag or something from Epic Designs!)
    R.I.P. Corky 10/97-4/09
    Disclaimer: I sell and repair bikes for a living


  12. #12
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    I bought the kit that included a black tensioner and 3 single cogs with the spacers to convert a regular mountain bike, but this frame has horiz dropouts.
    I would think the new single gears would be ready for a mountain bike chain.

    Bike is new, with no wear on the chain or front ring.

    Side note: The doctors had a lot of questions after they xrayed my face and head. I guess 30 screws and plates in my face didn't look to normal to them, lol

  13. #13
    I'm gonna have to kill ya
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    Wow you must have good scrap value with all that metal work :P

  14. #14
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    Quote Originally Posted by ATBScott
    I missed that little detail about it being 1x9 to begin with - but on the issue of SS conversion with the cog being wider - I have seen a number of kits that came with 3/32" cogs, as they would expect that someone may be converting over a formerly-derailleur equipped bike. That said, it COULD be a 1/8" cog and that would not let the chain drop into the trough of the tooth profile and cause problems (even split the chain side plates in some cases...) Also, even though it is not likely ramped, the 3/32" front ring, if you end up going with a 1/8" chain might let the chain slop around and cause problems. Homebrewed Components makes nice, very reasonably priced cogs and rings. Check what you have and if you need something, get his ring/cog and a KMC 1/8" chain and you should be set. And if you sue the Big S you will have tons of money to buy multiple rings and cogs and maybe even a Ti SS frameset. (Make sure you buy a seatbag or something from Epic Designs!)
    The problem is a 9 speed chain is on average .01" narrower than a 3/32" chain, which means that it can fit tight on even a 3/32" cog. The cheap stamped cogs that come in a kit are generally pretty close to 3/32" (i have some that are a few thousandths over, and some that are the same amount under, all from the same manufacturer). I just checked 3 different 3/32" stamped steel cogs. One fits fine, one comes close but not quite, and one doesnt fit at all.

  15. #15
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    Quote Originally Posted by makomyday
    I bought the kit that included a black tensioner and 3 single cogs with the spacers to convert a regular mountain bike, but this frame has horiz dropouts.
    I would think the new single gears would be ready for a mountain bike chain.

    Bike is new, with no wear on the chain or front ring.

    Side note: The doctors had a lot of questions after they xrayed my face and head. I guess 30 screws and plates in my face didn't look to normal to them, lol
    damn! metal detectors must be a PITA! Hope it wasnt all mtb related injuries.

  16. #16
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    Ooohhhhh.
    Sorry to hear about the injuries. Heal well
    Robb
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  17. #17
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    were you using a spring-loaded tensioning device? if it's being used in a push-down capacity, maybe the spring failed to do it's job. i could also see a stick getting caught in there causing this.

  18. #18
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    Could also be you pulled the chain too tight. The cog in your conversion kit was likely cheap, meaning there's a high chance it's not perfectly round. If you pulled it way tight on a loose bit of the cog, then cranked on it, you probably overcame the torque on your axle bolt/skewer, slammed the wheel forward getting it misaligned in the process and derailed your chain.

    Remember when you're setting your chain tension that you still want a little bit of slack/movement and remember to check for tight spots in the chain/cog.

  19. #19
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    Where in the pedal stroke did the chain come off?
    My kona hot isn't the stiffest bike, and my chain will occasionally come off due to frame twist. It always happens near the bottom of the pedal stroke. I guess because the frame is only flexing enough when my foot is pushing through the 3 o'clock position, the chain then derails as my foot is at about 4-5 o'clock. It happens quite gently, if standing, my foot just stops at the bottom. So I wouldn't think it would be the problem you are having.

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