I keep throwing my chain... driving me F ing crazy!- Mtbr.com
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  1. #1
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    I keep throwing my chain... driving me F ing crazy!

    I'm throwing my chain a couple of times per ride and I can't figure out why. It always happens after coasting through some ruff stuff, when I power back hard on the cranks. I'm tired of banging my knees on the forks.

    Bike set up:
    2010 Gary Fisher Superfly Single Speed carbon 29r
    Blackspire 34t on front
    Singleworks 17t rear
    Shimano HG chain

    Didn't have much trouble out of it when I first set it up, only threw the chain when it stretched and had too much slack in it. I currently have it tightened to to almost 0 slack in the tight spot of the rotation. Alignment was off by 1 spacer in the rear (figured out how to check it with a straight edge) I fixed that but it didn't help. Chain is showing 75% on a stretch guage.

    I've got a bunch of miles on it (1400 on front ring, 700 on chain and rear ring), guess I should replace the whole drivetrain but figured with my luck it'd throw the new chain too.

    Any suggestions before I start buying parts?

    Thanks!

  2. #2
    Out spokin'
    Reputation: Sparticus's Avatar
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    Quote Originally Posted by graluc
    ...

    Any suggestions before I start buying parts?

    Thanks!
    Check for a bent tooth on ring or cog.

    Check your chainline by measuring from centerline of bike to be sure it's perfect.

    Good luck.

    --sParty
    disciplesofdirt.org

    We don't quit riding because we get old.
    We get old because we quit riding.

  3. #3
    master blaster
    Reputation: veloreality's Avatar
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    Quote Originally Posted by graluc
    I currently have it tightened to to almost 0 slack in the tight spot of the rotation.
    there is no reason to have a tight spot. with a quality cog and chainring installed corretly you shouldnt have any problems.

  4. #4
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    Quote Originally Posted by veloreality
    there is no reason to have a tight spot. with a quality cog and chainring installed corretly you shouldnt have any problems.
    Could be a slightly eccentric crank spider.

    --sParty
    disciplesofdirt.org

    We don't quit riding because we get old.
    We get old because we quit riding.

  5. #5
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    I agree with Sparty! I suspect you have some worn teeth on either the front or rear. There is a chance that maybe you have a bent link in your chain as well which could be acting as a ramp if you will and just throwing it off.

    Also keep in mind that if you have almost 0 slack on the tight spot as you call it, that that means there is more slack where there is no tight spot and it may be just enough to allow the chain to catch on the edge of the teeth when you begin to pedal again.

    In my case, my wheel was simply slipping forward. But that is what happens when you have a GT Peace that did not come with the proper tension bolts and you had to buy your own to make it work properly. Sorry for the rant there.

  6. #6
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    Mr. Sparticus is right on.

    A quick check is look at your standing behind your bike so see if it's straight or not. It won't prove it's not the problem, but can easy prove it is.

  7. #7
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    Your chain ring could also be slightly bent if you banged it into a log over time. Just a thought. May not be a big bend but could be enough that it is causing the chain to catch and then throw.

    While standing over the bike look down at the chain line and spin the cranks. If anything moves side to side, this could be part of the issue. Just a thought.

  8. #8
    nothing to see here
    Reputation: Stevob's Avatar
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    Another idea to consider is unmounting your chainring, rotate it 180 degrees, and mount it again. It may just be that your loose spot is only at the point in the crank cycle that you begin to pedal again after coasting. Rotating it might help.
    I see hills.

    I want to climb them.

  9. #9
    Retro Grouch
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    Quote Originally Posted by graluc
    I'm throwing my chain a couple of times per ride and I can't figure out why. It always happens after coasting through some ruff stuff, when I power back hard on the cranks. I'm tired of banging my knees on the forks.

    Bike set up:
    2010 Gary Fisher Superfly Single Speed carbon 29r
    Blackspire 34t on front
    Singleworks 17t rear
    Shimano HG chain

    Didn't have much trouble out of it when I first set it up, only threw the chain when it stretched and had too much slack in it. I currently have it tightened to to almost 0 slack in the tight spot of the rotation. Alignment was off by 1 spacer in the rear (figured out how to check it with a straight edge) I fixed that but it didn't help. Chain is showing 75% on a stretch guage.

    I've got a bunch of miles on it (1400 on front ring, 700 on chain and rear ring), guess I should replace the whole drivetrain but figured with my luck it'd throw the new chain too.

    Any suggestions before I start buying parts?

    Thanks!
    Is this something that has just started, or has it been with your bike for a while? You say you have 1400/700 miles on your drive train, so I'm thinking this chain throwing thing may have recently cropped up. Either that or you installed some worn out parts on a new bike frame.What's the rest of the story?
    Just one more rep and I get the toaster!

  10. #10
    Oaktown Honkey on Strava
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    Laser !

    Just kidding sorta. I used a cheapo flashlight red laser to align first ss - funny I know. Beware of reflection! Anyway,one of the guys I ride with works at Performance Berkely and was howling at that story as he broke out a micrometer. Measered center of Btm Bracket, Rear hub, divided by two, and came off that center line for tensioner and rear cog. I couldn't believe how quiet the tensioner is. The bike I did w/ laser (laugh) has no tensioner and is perfect for last year. I agree w/ previous posts too.

  11. #11
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    Thanks for all the suggestions.

    I'm pretty certain that the alignment is dead on. Used the straight edge method I found on here. The chain ring was off of my previous bike, the chain and rear cog were new when I built this one. I would throw the chain since new if there was any slack at all in the tension. As long as I kept it super tight it was ok. Now it throws no matter how tight it is.

    So far I've inspected the rings again. The front show some signs of wear but nothing excessive, the rear still looks good. They are both umwarped as best as I can tell. I read some interesting posts on multi-speed chains vs. single speed chains on here too. I had an almost new BMX chain so I put that on it last night. It feels like it is spinning better now, more free. Maybe I just killed the chain. I'll post an update after my ride next week.

  12. #12
    aka "SirLurkAlot"
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    The suggestion regarding watching your chainring from above works well. It sometimes helps to take the chain off. You might also want to take it off the crank and lay it flat on a solid surface (ie bench or table).

    If the chainring and cog are fine, I would replace the chain.

    All this assumes that the chain isn't too loose when it's not in the tightest part of the revolution. That's been my experience when it comes loose after bouncing over a rough patch.

    Work piece by piece, take your time and let us know how it works out.

  13. #13
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    I had a similar problem on a bike with sliders. Turns out I was using PC-1 chains that Sram makes specifically for SS. They would continually stretch until breaking. Those chains suck! A new PC-1 chain was lasting me around 1-2 months. Finally some recommended an 8 speed chain and problem solved. It's been on for about 6 months with no issues.
    Truffle Shuffle

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