Chainring issues on new bike- Mtbr.com
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  1. #1
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    Chainring issues on new bike

    So I bought myself an 11' Rockhopper and I am already having issues. Probably because I'm uneducated and just ramming about things but I'm still just a little confused.

    I went on a ride today, my fourth after buying my ride Monday, and I bent my 2nd sprocket or my 2nd chainring. (I might be using the wrong terms) I was on a some what severe climb and I had decent momentum. I started climbing and putting a decent power stroke on the bike then boom, the chain popped and I pull over to see that the chain was bumped off of the 2nd sprocket and was wedged in between it and the frame. It was wedged in so tight I had to smash it out with an allen wrench and a rock. After examining everything, the chainring was bent to hell.

    I'm just wondering what went on down there... I didn't shift with a load on the drivetrain, I was in a decent gear to keep tension on the chain. I'm just trying to learn more about what's going on. Any ideas?

    Do you think that either my LBS or Specialized will help me out a bit since it's a brand new bike?

    Thanks.

  2. #2
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    Sounds like the front derailleur adjustment may have been off a tick. Happens to the best of us and the result is that the chain gets tossed and might jam like yours did. I know you likely felt like you were in a jam (pun intended) and needed to do what you needed to do to continue on your way, but maybe it wasn't a great idea to go all caveman on it.

    The spec for the crankset on a 2011 Rockhopper (base model?) is a Suntour unit with an Octalink bottom bracket. Doesn't say if the chainrings are replaceable (bolted on) or riveted in place. If the chainrings are riveted, the whole crankset would need to be replaced.

    To be honest, the sooner you wean yourself from running back to the LBS everytime you have an issue and start doing things for yourself, the sooner you'll start saving a lot of money. You can try to see if the shop you bought from will help you out or take (some) responsibility for what happened. Maybe they will. If not (and this is ME speaking for ME) I would walk out and make that the first day of the rest of my cycling life, vowing to be as self-reliant as possible. Learn how things work and how to work on them.

    You can get an Octalink style Shimano Alivio crankset from Jenson for $35 that has replaceable chainrings. You will need a crank arm remover and some allen wrenches, but they will pay for themselves in short order.

    This is an excellent resource for repair help:

    http://www.parktool.com/blog/repair-help

    And here is the specific section(s) for what you need to do:

    Crank arm:

    http://www.parktool.com/blog/repair-...ve-or-octalink

    Front derailleur adjustment:

    http://www.parktool.com/blog/repair-...ur-adjustments

    JMHO.

  3. #3
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    Judging by the specs on the Specialized website, the chainrings are replaceable even on the basic model. A decent LBS will probably charge you for a new chainring, but not for work.
    I agree with JeffJ, the earlier in your cycling life you start wrenching on your bike, the more money, time and nerve cells you save.

  4. #4
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    Wow. Thanks so much for your help guys.

    Yeah, going all caveman wasn't probably the best idea but I am no where near educated and thought I was working with the only solution... lol. Still just an ignorant newb...

    I am totally along the lines that you guys are suggesting. I want to know how to get a bike riding the way it needs to and do it by taking the initiative.

    Awesome, good to know this is a relatively cheap fix. Is there any type of chainring that has better durability? Are they all made from the same general grade aluminum or is it worth the extra dough for the seemingly higher end models? I've heard some rings last longer and don't have tooth wear as soon.

    Also, I'm not sure if this has anything to do with what went on but on my first ride with the bike, I could hear the front derailleur making a repetitive rubbing noise. It was only when I was in the second sprocket. Could this have possibly meant that it was slightly bent to begin with? I'm not sure if my logic is making sense, but if it was just the derailleur being off a bit, wouldn't the rubbing be a constant sound?

    Thanks so much for you help guys. Incredibly helpful. Can I buy you a brew?

  5. #5
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    This seems a bit unusual to me. I've had the chain drop from the middle ring to the small ring, but it's never dropped completely off from the middle ring.

    While it's a good idea to learn to do the wrenching yourself, I would take it back to the shop in this instance. They will probably be able to straighten the bent ring. It's possible that it came bent. If it were to bend again after it's repaired, I wouldn't bother replacing a ring. Just move on to a better crankset.

    A rubbing noise when on the second ring means the cable needs to be adjusted with the barrel adjuster on the shifter. If the chain had jumped off from the small ring, that would indicate that the limit screw needed adjustment. Check the link Jeff posted.

  6. #6
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    Also, if you look closely at the chainrings, you'll notice that they are not uniformly cut/ground. They are cut to optimize the shifting points at two places on a single revolution and you will see the cuts differ leading up to those points. Many chainrings also utilize pins that act as 'ramps' to further aid shifting.

    The rubbing not being constant could be due to the different cuts on the teeth. I would go so far as to say that this is actually normal when the chain just starts to rub the derailleur cage. If this is on the middle ring, then you would use the cable adjuster to adjust this by backing it out until it (barely) no longer rubs when in 1st gear (the largest cog in back). If it rubs on either the large or small chainring, then that is adjusted using the 'stop' screws on the front derailleur itself.

    As mentioned ablove (and I can see this now that I took the time to blow up the pic on the Specialized website), it looks like your crankset does have replaceable chainrings. The availability of Suntour chainrings may be another matter altogether, but from the looks of them, there is a chance that Shimano chainrings could be sub'd

    There are also rings that have teeth that are uniformly ground, but they are generally for singlespeed applications. You don't want those.

  7. #7
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    Ahhhh ok. So with those shift ramps, the chain may have a slight wave in its path?

    Maybe I just had a small rock tossed up in between the chainring and chain? It's good to see that this is a fairly cheap repair if the LBS doesn't help me out.

    Will any 4 bolt chain ring be compatible? And if so, should I just count the teeth on mine to figure which one I need?

    Also, I ride to school on this bike and was thinking about a bashguard. Are there any cons with one of those? And how does that fit in with the whole chainring setup? Is there room for a bashguard with a 3 ring crankset?

  8. #8
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    SR Suntour Service

    Quote Originally Posted by mr.shiggles
    So I bought myself an 11' Rockhopper and I am already having issues. Probably because I'm uneducated and just ramming about things but I'm still just a little confused.

    I went on a ride today, my fourth after buying my ride Monday, and I bent my 2nd sprocket or my 2nd chainring. (I might be using the wrong terms) I was on a some what severe climb and I had decent momentum. I started climbing and putting a decent power stroke on the bike then boom, the chain popped and I pull over to see that the chain was bumped off of the 2nd sprocket and was wedged in between it and the frame. It was wedged in so tight I had to smash it out with an allen wrench and a rock. After examining everything, the chainring was bent to hell.

    I'm just wondering what went on down there... I didn't shift with a load on the drivetrain, I was in a decent gear to keep tension on the chain. I'm just trying to learn more about what's going on. Any ideas?

    Do you think that either my LBS or Specialized will help me out a bit since it's a brand new bike?

    Thanks.
    If, in fact, you have an SR Suntour crankset on your bike I would suggest you give Shawn a call at our Warranty Service Center. (360-737-6450) - He may be able to help you out with a replacement chainring.

    Take note that those chainrings are heat treated to achieve the necessary strength. While I don't know the exact conditions that caused the chainring to bend, it is pretty rare for this to happen. It may be that the chainring was not heat treated to specification and thats what caused the failure.

    Take care..............Doug

  9. #9
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    Well done Doug

  10. #10
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    Yeah you da man Doug!!!

    I shot them an e-mail and will give them a call in the morning!

  11. #11
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    (In case anyone is in this same position, here's what they did for me.)

    Called the warranty department at Suntour. They said to head back to my LBS and they'll be able to take care of a replacement chainring via Suntour.

    Thanks for your help guys and maybe gals. I appreciate it.

  12. #12
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    (In case anyone is in this same position, here's what they did for me.)

    Called the warranty department at Suntour. They said to head back to my LBS and they'll be able to take care of a replacement chainring via Suntour.

    Thanks for your help guys and maybe gals. I appreciate it.

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