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  1. #1
    mtbr member
    Reputation: farmertan's Avatar
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    Skipping middle chain ring

    OK guys, I'm stumped on this one (no pun intended). I have an 07 Stumpjumper Pro with XT cranks and a SRAM PC 951 chain. Whenever I crank hard over a series of roots on up a hill and hit a good size bump, the chain ring skips, makings a horrendous noise and coming close to throwing my knee into the stem.

    Iím running one spacer on the drive side and the chain line looks spot-on. A buddy of mine just build 2005 Stumpjumper 120 with the same components and has the same issue. Iíve been wrenching on mountain bikes for 10 years and canít figure this one out. Any suggestions?

  2. #2
    I Love my Rize
    Reputation: danoalb's Avatar
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    Tell me something

    Are you both running Shimano rear derailleurs and how old is your drivetrain?
    Early to bed early to RIZE makes a man healthy, wealthy <(scratch that) and wize.

    RIGHTY on a LEFTY

  3. #3
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    I went through the same thing when I put an XT crank on my '04 Epic.I tried different chains, cassettes, wheels etc. and it always slipped on the middle chainring just as you described. I finally put the middle ring from my old LX on and it worked fine. Shimano sent me a new middle ring, (without admitting they had a problem), and it did the same thing. In frustration I replaced it with a titanium ring from another manufacturer. A few months later I contacted Shimano again (this time they admitted a problem) and they sent me another middle ring that was supposed to be an improved design. I have not gotten around to trying this ring yet. It works fine with the TI ring and I'm not sure that I want to screw with it.

    Barry

  4. #4
    mtbr member
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    SRAM X.9 rear, Shimano XT front

  5. #5
    I Love my Rize
    Reputation: danoalb's Avatar
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    Crappy XT ring

    Quote Originally Posted by farmertan
    SRAM X.9 rear, Shimano XT front

    The XT rings are well known for being total JUNK.
    Like the previous poster said I heard they had big problems with their middle rings. If I were you I would replace the middle ring with a steel deore m510 one and problem solved. I would also change the granny to a steel deore also. Alu rings have no place on a mtn bike except for the big ring if you run them as you don't hammer the big ring and you spin it more. The steel rings will last way longer than the garbage alu ones and are much tougher. The weight difference is minscule. Most people I know with XT cranks switched to steel rings for the granny and middle. Here are some links for a cheap granny and middle m510 Deore steel rings. If it is a hollowtech II crank use the m580 LX steel granny.

    22t LX m580 steel granny,,,, http://store.airbomb.com/ItemDesc.asp?IC=CR5808

    22t granny.... http://store.airbomb.com/ItemDesc.asp?IC=CR2997

    32t middle.... http://store.airbomb.com/ItemDesc.asp?IC=CR2998
    Last edited by danoalb; 03-23-2007 at 06:30 PM.
    Early to bed early to RIZE makes a man healthy, wealthy <(scratch that) and wize.

    RIGHTY on a LEFTY

  6. #6
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    Caution;  Merge;  Workers Ahead! Skipping Middle Chainring!!!

    Wow! Here I was thinking I was absolutely crazy and someone else is having the exact same problem as I am...

    I just bought my 2007 Specialized Stumpjumper Pro Carbon 2 days ago and this is not the beginning of a great appreciation for the machine.

    I am currently in a ton of pain as I actually did spin out in the worst possible way. I not only smashed up my knee really bad, I also pulled out of my pedal in order to avoid falling backwards down the steep edge I was climbing and ripped up the backside of my leg. It was a pretty bloody ride home I must say. I kept swearing something was not right about the middle chainring and could not figure out the problem, but here are others with the same issue.



    What should I do? How do I convince my dealer to fix this issue? Should this turn into legal action against Shimano and/or Specialized? Why isn't there a recall on this issue?

    I worked really hard to afford something this nice and now I get my leg banged up from a defective part? No other solution other than to simply ignore this and buy some steel replacement rings?

    Truly bummed....


  7. #7
    It's carbon dontcha know.
    Reputation: 6thElement's Avatar
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    There's a big thread about the issue here:

    http://forums.mtbr.com/showthread.php?t=212224

  8. #8
    mtbr member
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    Replacement ring

    I got a replacement ring (warranty) from Shimano yesterday. Shimano admitted that there was a problem on some FS bikes. The ring looks the same but has a slightly different part number. I installed the ring last night and I'm heading out in 20 minutes for a ride. I'll let y'all know how it turns out...

  9. #9
    mtbr member
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    No skipping

    The replacement ring from Shimano worked great. Not one slip.

  10. #10
    mtbr member
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    Skipping Middle Chainring!!!

    Thanks for the information. I figured I would cut to the chase and simply go buy myself a new chainring and slap it on there and be done with this problem.

    I returned back to my LBS and first asked them to check over my bike and verify everything was in perfect operating order. They assured me everything was perfect and the scenario I described to them seemed really far fetched in their opinion. I also agreed with them except for the fact that I knew it could actually happen. They told me to leave the bike with them for a few days to determine if there was more they could find wrong. I politely disagreed and stated that I simply wanted to purchase an LX Deore 32t chainring which I saw sitting up on the shelf. The owner of the shop thought I was nuts, but he gave me the benefit of the doubt. He installed, tuned and gave me the chainring for no charge whatsoever! He held onto the defective chainring to have a word with his Shimano rep upon hearing back from me. Tomorrow I am going to inform him that after 30 miles in the roughest sections of trails I could possibly imagine, I have yet to skip when riding in my middle chainring, or any chainring for that matter!

    Cheers!
    CoffeeBean...

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