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  1. #1
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    Chain jumping out of large ring on harder efforts?

    I have a Shimano Ultegra di2 set up, 53/39 in the front with a 28-11 in the rear. Chain is tight and not worn, and derailleurs are adjusted correctly.

    I am having an issue with my chain coming off to the outside of the large ring when I am lower in the rear cog, anything in the 13,12,11. It has happened twice on a steep and fast downhill with a couple bumps under moderate power, and once when I was sprinting in the 53/12 under high power(I was sprinting so as much as I could put out anyway). Before this happened everything worked fine, and shifted normally. I have adjusted the front derailleur so that it is almost rubbing on the chain on the outside of the big ring to act as a chain catcher or sorts, but is there another reason that I should look towards to fix this?
    Thanks for the help!

  2. #2
    tlg
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    Did you check the height and angle of your FD?

    Check for bent teeth on your chainring.

  3. #3
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    Quote Originally Posted by tlg View Post
    Did you check the height and angle of your FD?

    Check for bent teeth on your chainring.
    Yea the height is fine and it is angled correctly. The weird thing to me was that if it was a front derailleur issue I would think that it would happen all of the time not just under increased load.

  4. #4
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    Things can flex around quite a bit when you are humping down on the peddles. I would check for a loose bearing or crank arm. If they chainring is slightly bent is may be very bent under load.

    Ride Safe,

    Joe

  5. #5
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    Quote Originally Posted by bmwjoe View Post
    Things can flex around quite a bit when you are humping down on the peddles. I would check for a loose bearing or crank arm. If they chainring is slightly bent is may be very bent under load.

    Ride Safe,

    Joe
    It just had the crank off about 500km ago, so I would hope everything is still nice and tight in there. I will check that out and see if the chain ring is noticeably bent or off
    Last edited by misterwaterfallin; 06-13-2013 at 03:02 PM.

  6. #6
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    Chain was installed in the correct direction, right? Newer Shimano chains are unidirectional, though I'm not sure if/why improper orientation would do this.

    Otherwise I'd think the chain is still a bit long, which can be a bit sensitive since you're running an 11-28.

  7. #7
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    Quote Originally Posted by Ventruck View Post
    Chain was installed in the correct direction, right? Newer Shimano chains are unidirectional, though I'm not sure if/why improper orientation would do this.

    Otherwise I'd think the chain is still a bit long, which can be a bit sensitive since you're running an 11-28.
    Yes right direction. I thought it might be a bit long but when it is in the 53/28 it is very tight, so tight I don't think I can remove a link without it seizing up.

    What was weird to me is that it just started happening. I race a crit on Saturday with quite a few out of the saddle sprints and I was there at the end sprinting for the line with no issues. Come Tuesday of this week and it falls off.

  8. #8
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    Did you check for any kind of frame damage? FD mount cracked, cracked BB? Sometimes these kinds of mysterious issues crop up because some component got compromised, somehow. Try to grab your FD cage, and see if it somehow behaves unusually. Same with your cranks, and chainrings. Any lose bolts anywhere? Cracked chainstay or seatstay? What you are describing is extremely unusual, so something is fishy here...

  9. #9
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    I did check for something being loose/bent. I grabbed both crank arms and flexed it back and forth as hard as I could and it wasn't loose or really flexible at all. I am having a Quarq installed next week so at that point I will make sure that everything gets a solid once over but there isn't any damage from wheat I can tell

  10. #10
    wyrd bi ful rd
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    Just wondering if you have managed to resolve this issue ... curious as to what is happening ...

  11. #11
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    Quote Originally Posted by c_h_i_n_a_m_a_n View Post
    Just wondering if you have managed to resolve this issue ... curious as to what is happening ...
    I did...by putting on a Sram Red Quarq.

    I think the issue was a slightly bent tooth on the outer ring. It was causing the chain to roll over towards the outside, and with enough force it would pop off. Rotor cranks are garbage in my opinion, I certainly won't be running one after this.

  12. #12
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    Chain jumping out of large ring on harder efforts?

    Rotor chainrings you mean? Don't know how/why a crank would lead to a bent tooth on the chainring.

    Were you using the round or oval rings?
    A road bike needs disk brakes like a fish needs a bicycle (with apologies to Ms. Dunn)

  13. #13
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    Exactly, chainrings.

  14. #14
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    You have Ultegra Di2 and you opted for Rotor chainrings?

  15. #15
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    The OP problem is characteristic of a worn large chainring (aka sharkteeth). So, yeah, changing the crankset will fix that too.
    * not actually a Rock Star

  16. #16
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    Quote Originally Posted by Ventruck View Post
    You have Ultegra Di2 and you opted for Rotor chainrings?
    That's how the bike came, I didn't opt for that. Presumably it came that way to save money on the manufacturers end.

    Quote Originally Posted by Creakyknees View Post
    The OP problem is characteristic of a worn large chainring (aka sharkteeth). So, yeah, changing the crankset will fix that too.
    Under 1000km on the set, so not overly worn. They may have been bent from the front derailleur pushing the chain over under load or something weird like that. Either way I'm glad to not be using them any longer

  17. #17
    wyrd bi ful rd
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    Can you post pictures? From the side and front profile of the bent tooth?

    If the tooth is bent then possibly from hitting something on the ground? Would not think that the derailleur pushing the chain over under load will bend the tooth on the chainrings ...

  18. #18
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    Quote Originally Posted by Ventruck View Post
    You have Ultegra Di2 and you opted for Rotor chainrings?
    Quote Originally Posted by c_h_i_n_a_m_a_n View Post
    Can you post pictures? From the side and front profile of the bent tooth?

    If the tooth is bent then possibly from hitting something on the ground? Would not think that the derailleur pushing the chain over under load will bend the tooth on the chainrings ...
    I already attempted a straightening job which worked and got me through my race last Saturday so there's not much to show at this point. It was very evident what was happening. By turning the crank you could see the point that the chain would try to roll off of the chain ring

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