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  1. #1
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    Newbie broke something needs help.

    Hi, guys I did some searching around and did not really find exactly what I needed. So I apologize if this has been answered a gazillion times in the past already. I bent the second gear on my crankset(sorry if my nomenclature is nowhere near correct) and now a couple of the teeth are all buggered up. I thought it would be a simple process of looking around on amazon and finding a replacement part but apparently there is not a one size fits all fix The local bike shop quoted me $200 bucks for the part and install but i am not really looking to drop that much money into the old girl. Any help that could be offered would be highly appreciated, I really just need some information about where to find some information about what part i need or what that part is exactly. The bike is a Trek that I bought back to get back and forth to college back in probably 03 and after a knee surgery last year I am just not able to jog anymore so I have been getting into bike riding. Managed 22 miles last saturday before I murdered it


  2. #2
    Andrew R Stewart Andrew R Stewart's Avatar
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    Interesting Trek model name "GT"...
    Since getting something so straight forward as the correct name (or was it photoing the correct bike in the garage?) is hard to do I suspect that the OP might not be able to measure the crank's bolt pattern, count the middle ring's teeth and then search on line for a match. Sometimes there's a reason the LBS is the way to go. Andy.

  3. #3
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    I just posted my first post as a 'newbie' with a bike problme also. granted i was able to at least know the brand and model of my bicycle but a scathing and sarcastic answer is just what a place like this needs from a near 3000 post veteran to encourage new users. I truly hope all the forumers on here are not like you sir.

  4. #4
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    If you don't like then possibility of getting corrected, here isn't the best place to post with obviously inaccurate details. You asked a question, and gave inaccurate information vs the picture, all that was said, was to correct your information. For the bike, it's a GT i-drive, Timberline model 2001 GT Timberline iDrive - BikePedia, I had a l XCR version a few years ago, nice ride, but not that light, and can feel as though you are perched on the bike when riding.

    For the crank, you may get away with just filing the broken teeth so they don't interfere with the shifting or anything else, if a complete crank is needed, you will need a square tapered one, preferably with 22/32/42 teeth, a Shimano Atlus M311 has this, or the Acera M391 (looks a lot nicer) comes with a 44t outer, your chain may work with this, buy you probably would need a new one to cope with the extra t on the outer.

  5. #5
    Senior Member awfulwaffle's Avatar
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    Someone correct me if I'm wrong, but isn't it supposed to be that way to aid in downshifts?

  6. #6
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    Are you sure the chainring is bent and that the teeth are damaged?

    Virtually all cranksets manufactured in the last 20 years or so have been designed with ramps and twists and teeth of uneven height to improve shifting efficiency. Go to a bike store and look at the chainrings on the mountain bikes on display and compare them to yours.

    If they look approximately the same and if your bike shifts correctly, I'd stop worrying about it.

  7. #7
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    Quote Originally Posted by awfulwaffle View Post
    Someone correct me if I'm wrong, but isn't it supposed to be that way to aid in downshifts?
    Check the teeth at the 11 o'clock, they look very wrong, as in damaged, not machined for purpose.

  8. #8
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    I apologize for getting Andy all riled up, but I guess every forum out there has those that have to go out of their way to be insulting but whatever puts a smile on your face and gets you through the day. The fellow at the bike shop I took it too was quoting me Trek parts so I was under the assumption it was a Trek bike. Sorry I offended you with my gross negligence.

    Jim, thank you that is exactly what I needed much appreciated!

  9. #9
    Senior Member awfulwaffle's Avatar
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    Quote Originally Posted by jimc101 View Post
    Check the teeth at the 11 o'clock, they look very wrong, as in damaged, not machined for purpose.
    Maybe, but check this thread: Broken teeth on chainring

    Seems like the OP there is describing exactly what our OP has shown in his picture.

    @paintgod93 : Hold on before going back to your LBS and getting new parts ordered. I'll take a look at both the old and new cranksets for my MTB when I get home to see if they look like yours. In fact, the old one is a riveted chainring Suntour one just like yours, so it should provide a good comparison.

  10. #10
    Senior Member Campagnono's Avatar
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    Quote Originally Posted by paintgod93 View Post
    I apologize for getting Andy all riled up, but I guess every forum out there has those that have to go out of their way to be insulting but whatever puts a smile on your face and gets you through the day. The fellow at the bike shop I took it too was quoting me Trek parts so I was under the assumption it was a Trek bike. Sorry I offended you with my gross negligence.

    Jim, thank you that is exactly what I needed much appreciated!
    I have always been afraid to post anything here, ever.

    It seems like there are a great number of participants here with unlimited knowledge and time reserves, and they are all-too-eager to point out the logical, mechanical, and even grammatical failures of others. Wish it was more inclusive and polite, but indeed, there are a lot of folks here with a lot of good info.

    As you wait for the thickness of your skin to adjust, Sheldon Brown's site offers a wealth of non-hostile, non-aggressive information, all without the mocking this place is famous for...

  11. #11
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    Quote Originally Posted by awfulwaffle View Post
    Maybe, but check this thread: Broken teeth on chainring

    Seems like the OP there is describing exactly what our OP has shown in his picture.
    Have you looked at the teeth at 11 o'clock on the OP's photo? they are not what you expect for profiled teeth, have a look at the example below, at the same location as the Op's there is no profiling, on the OP's, the 'profiling' is sudden, and indicating that there is probably damage, such as from hitting a kerb.

    suntour crank.jpg

  12. #12
    Andrew R Stewart Andrew R Stewart's Avatar
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    Quote Originally Posted by paintgod93 View Post
    I apologize for getting Andy all riled up, but I guess every forum out there has those that have to go out of their way to be insulting but whatever puts a smile on your face and gets you through the day. The fellow at the bike shop I took it too was quoting me Trek parts so I was under the assumption it was a Trek bike. Sorry I offended you with my gross negligence.

    Jim, thank you that is exactly what I needed much appreciated!
    No offence taken, I don't get riled too easily. My reply was meant in all seriousness.

    One of the questions I get at work (frequently and for many years) is whether "I" (the customer) can fix the bike "myself". I usually give a quick list of the tools and basic process. Based on the customer's response I suggest that they give it a go, and if they get stuck we (the shop) will pick up the rest of the job, or I suggest that they probably should let a more experienced person do the job. When I see the "deer in the head lights" look while I'm explaining things I usually say the latter. When I read the OP's question I saw that look, in a manor of speaking.

    It's too bad this medium is so limited in the nuance of communication, or that I can't write well enough to have the difference between gentle satire and flaming be better understood. A

    But in my defense I did give actually correct and asked for advise. Many of the following posts give more detail and ask equally valid questions. Andy.

  13. #13
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    Someone pointed out recently that "I bent my chainrings"/"The bike store sold me a bike with worn chainrings" threads might be the most common threads in this forum, especially in threads started by self-described newbies. I haven't yet seen one of those threads where the chainrings turned out actually to be bent. That photo of black chainrings against a light background is difficult to interpret, but it sure looks like the usual arrangement of full-length teeth alternating with blunt and twisted teeth as found on brand-new inexpensive mountain bike chainrings.

    If something happened during a ride that resulted in shifting problems (reading between the lines of the original post), I'd check the front derailleur, or take it to a bike shop to be checked. It looks as it if may have been knocked out of alignment with the chainrings, and it is certainly not positioned within a couple of millimeters of the outer chainring as it should be.

  14. #14
    Senior Member awfulwaffle's Avatar
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    Quote Originally Posted by jimc101 View Post
    Have you looked at the teeth at 11 o'clock on the OP's photo? they are not what you expect for profiled teeth, have a look at the example below, at the same location as the Op's there is no profiling, on the OP's, the 'profiling' is sudden, and indicating that there is probably damage, such as from hitting a kerb.

    suntour crank.jpg
    A valid point, though I do seem to see the same 2 teeth exactly opposite the crank arm, offset 90 degrees from the position in OP's photo. Again, I'm not sure. Like I said, I'll check around when I get home.
    Last edited by awfulwaffle; 07-16-14 at 01:45 PM.

  15. #15
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    A good question might be: What happened and what exactly is wrong when you are riding the bike?

    The pictures aren't clear enough to see a problem. As others have stated a lot of chain rings are asymmetric so a newb might think there is a problem by looking at it because they don't understand what they are looking at. But if OP took it to a LBS and they think it needs replacing than maybe the chain ring is bent ....maybe. I find it hard to believe that $200 is the most economical option to replace a chainring. I would think a cheaper crankset could be bought an installed for less.
    http://www.pedalroom.com/members/rms13

  16. #16
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    You can go to Ebay or other internet sites and buy a ring replacement yourself. For example :

    Chainrings | Chain Reaction Cycles

    Make sure the tooth number and boltCircle number match your original, broken chain ring. I have never replaced a ring myself so cannot speak to that. But it seems like an okay job with an allen wrench. As you can see the ring themselves aren't cheap either. So maybe it makes sense to buy a new crankset. But beware, make sure it is compatible with your bottom bracket.

    If it gets too complex you might need to seek a more reasonably priced bike shop/co-op.
    65% of all statistics are made up on the spot. - DD

  17. #17
    coprolite fietsbob's Avatar
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    You were hopping over something across the trail? drag the chainring across a Rock or concrete or a Log?

  18. #18
    Senior Member Wilfred Laurier's Avatar
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    i agree with andy

    while changing chain rings is not rocket surgery
    it takes some knowledge to properly select a chainring
    that will match the crank and chain

    and then the crank and bottom bracket assembly usually has to be disassembled
    and the chainring(s) replaced
    and the whole thing put back together
    including likely derailleur adjustement

    now i am all for do it yourselfing everything possible
    but given the misidentified bike
    and the fact that the op referred to the visibly damaged big chainring as
    the second gear
    both led most posters on a wild tooth chase
    and
    betrayed the op as someone who should be consulting an experienced person
    who can lay hands on the bike

  19. #19
    Senior Member awfulwaffle's Avatar
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    Wellp, mine has the same thing in two places. Directly behind the crank arm, and exactly opposite. Both sets of lower profile teeth seem to be a tooth away from the nearest shift pin. Dunno why it's offset 90 degrees, but if I were the OP I'd check the opposite side of the chainring for where these two teeth are in relation to the nearest such pin. Take this as you will.




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