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  1. #1
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    Chain skipping and falling off

    I have a problem with chain skipping on my Dean Colonel 29er. It’s got about 250 miles on it. The drive train is Sram X0 in back and Shimano XT in front with X0 shifters. When I’m really torquing the cranks while I’m on the center chain ring and on about the third to fifth sprocket (from the inside) in back and I hit some rough trail that bounces the rear end, the chain skips. The skip seems to be at the front, not the back. Worse than that, at least three times when I’ve been pushing up a short hill in those gears, the chain has come off and fallen on the bottom bracket inside of the smallest chain ring. The front derailleur will still be positioned on the middle ring.

    Thinking that the front derailleur might be out of adjustment, I’ve increased cable tension so that the chain will barely drop from the large to middle, but that didn’t help. The chain length seems spot on. Large to large has the rear derailleur stretched so that the chain is almost going straight through the pulleys.

    Any suggestions?

    Thanks.

    ChuckD
    Last edited by Monument247; 07-24-2006 at 08:04 PM.

  2. #2
    Over the Hill
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    This won't address all the problems you are having. My 5-Spot was dropping the chain off the granny onto the frame. In rock gardens had to stay in middle ring to keep tension on chain.

    Tried this and has worked well http://www.ajsbikeparts.com/web-AJBIKEPARTs/AJ's Frameguard.htm

    Now the skipping sounds like a weak spring in rear derailleur...borrow another derailleur...see if it helps.

  3. #3
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    I had this same problem and it was driving me crazy. I ended up replacing the middle chain ring and it solved the problem.

  4. #4
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    Just curious...

    Quote Originally Posted by Martin6
    II ended up replacing the middle chain ring and it solved the problem.
    What was wrong with the old middle ring that caused it to skip and fall off? Just worn out? Bent? Missing teeth? Something else?

  5. #5
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    Kevin,

    I couldn't visibly see anything wrong with the old chain ring besides just normal wear. The bike only had a dozen rides on it at the time. I had already replaced the chain and cassette with no luck. It wasn't until I put the front tire against a wall and applied pressure on the pedal that I could see the chain was slipping on the chain ring. This is on an 06 Epic Marathon.

  6. #6
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    For the front derailleur you will need to adjust the low limit screw in order to get the derailleur cage to keep the chain on.

    Try swapping out the rear deraileur, your chain could also be too long but I doubt that would be the case on a new bike.

    hehe.. I'm so used to being in a shop when giving advice not trying to diagnose over the Internet

  7. #7
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    Quote Originally Posted by Popps
    For the front derailleur you will need to adjust the low limit screw in order to get the derailleur cage to keep the chain on.
    Good advise. I did make the adjustments to the front derailleur as Popps suggests, because I was having the same problem of the chain falling to the BB when it would slip. All is good now.

  8. #8
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    I got some good news today, in a way. It seems that my problem is a known problem with the new Shimano XT middle ring shift ramps. They advise using an LX middle ring until they work out a fix.

    Thanks to everyone for the replies.

    ChuckD

  9. #9
    Soft AND Tender
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    Monument247,

    Can you elaborate on the "problem" with new XT middle rings? I just put a new one on and experienced the skipping thing this weekend when riding.

  10. #10
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    Porblems with LX chain rings also

    Just a head's up, I had a brand new LX crank and chain rings on my brand new bike, and had the same problem, every thing was brand new. I finally replaced the middle chain ring with a Tru Vativ and have had no other problems. The point is that the new LX middle chain rings may have problems as well. At least I had problems with mine.

  11. #11
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    redclayrambler - Where did you get the Truvativ ring? What did it cost? I see one at Jenson for $24.48.

  12. #12
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    Any compatibility issues with the Truvativ middle ring in between Shimano chain rings?

    Also, for everyone here having this skipping issue, what chain are you running?

  13. #13
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    Quote Originally Posted by redclayrambler
    Just a head's up, I had a brand new LX crank and chain rings on my brand new bike, and had the same problem, every thing was brand new. I finally replaced the middle chain ring with a Tru Vativ and have had no other problems. The point is that the new LX middle chain rings may have problems as well. At least I had problems with mine.
    Yup same here, same exact problem with a brand new LX crankset. Switching from and 8-speed to 9-speed chain seems to have helped the problem a LITTLE bit, but it's still happening. I'll be replacing the rear derailleur soon (it's ten years old, and a little worn out), and the middle chainring if that doesn't fix it.

    edit: Ok, I just got off the phone with Shimano. They confirmed that this is a known problem with the XT chainrings, but that my case is the first they've heard involving LX chainrings. The guy was a little suprised, since they've been sending out LX rings to the affected XT owners, which seem to be fixing the problem (BTW, the new chainrings are free under warrantee).
    Last edited by tick; 07-26-2006 at 03:52 PM.

  14. #14
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    cbratt - The problem is pretty well explained in the initial post.

  15. #15
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    Actually I find the best and cheapest replacement is an old Deore middle ring, they're string as hell and cheap. I had to do the same thing with the middle ring on my RF RideXC cranks when I first got my bike with them. Also had to replace the Shimano XT HT2 middle ring when I got that in only amonth or so, but that I think was due to a worn chain, but it did tend to "fall off" before it started skipping.
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  16. #16
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    Well I just got back from my LBS... I explained the problem with the middle ring to them, and got them to call Shimano to verify that this is a known issue. I should have my (free) replacement chainring from Shimano in a week or so . If this doesn't work, then I'll buy a middle ring from a different manufacturer. No sense in spending money on a new chainring for a brand new crankset, right?

  17. #17
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    Ok, I just got off the phone with Shimano. They confirmed that this is a known problem with the XT chainrings, but that my case is the first they've heard involving LX chainrings. The guy was a little suprised, since they've been sending out LX rings to the affected XT owners, which seem to be fixing the problem (BTW, the new chainrings are free under warrantee).
    Thanks for the heads up on the warrantee from Shimano. I'll make the call tomorrow for a new chainring.

  18. #18
    surly and rigid
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    Just a quick note. Most other rings aside from shimano will not work great on a shimano crankset. Watch the spacing. Good luck

  19. #19
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    Any compatibility issues with the Truvativ middle ring in between Shimano chain rings?

    Also, for everyone here having this skipping issue, what chain are you running?
    redclayrambler - Where did you get the Truvativ ring? What did it cost? I see one at Jenson for $24.48.
    I got the chain ring from a local bike shop, and I think it cost about twenty something.
    I was not sure at all if the Tru Vativ would play nice with the other Shimano stuff, but the guy at my shop said it should not be a problem, and he was right it seems to work just fine.
    Unfortunatey I don't know what model Tru Vativ ring it is, but they were both 32 tooth with shifting ramps.
    Hope that helps.

  20. #20
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    same exact issue here

    Monument247, did the LX middle ring fix the problem? This is driving me crazy too.

    On my Turner FLux I have a brand new 32T XT middle ring (M760 crankset) and I am having the exact same issue described in your original post. The combination of being in the middle ring, 3rd to 5th cog , bumpy terrain, and applying serious torque to the pedals results in a horrible grinding/popping. If I can, I try to look down to see the trouble while it is occuring and I have seen the chain halfway off of the middle ring even though I never shifted. The grinding noise is the chain trying to climb back up onto the middle ring while under torque.

    I have checked the following:
    -New SRAM PC 990 cassette
    -New SRAM PG 991 chain
    -New Shimano XT 32t middle ring
    -Chainline when in the middle ring and middle cog is straight
    -One BB spacer on the drive side with Shimano M760 crank set + 73mm bb shell
    -In my big ring / big cog combo my rear derailleur is stretched tight, but I can shift into this big/big combo without blowing things up
    -checked for stiff chain link
    Eat Food. Chop Wood. Ride Bike.

  21. #21
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    I just mounted a XT hollow tech II crankset. I had some issues setting up the FD.

    I was surprised but had to lower the FD about 3mm to match the shimano spec of 1-2 mm clearance. The old cranks were Race face.

    Problems went away.

  22. #22
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    Dave in Driggs wrote: "Monument247, did the LX middle ring fix the problem?"

    I don't know, yet. I don't think that I'll see the replacement ring until next week. I'm confident, though, that it'll fix the problem. Why don't you call the place you bought the bike and get them to call Shimano for a replacement ring? It sure sounds like you have the same problem. While waiting, my temporary solution is to run on the small ring with the rear on the outer sprockets which gives me similar ratios. No skipping problems that way.

    jeffscott - The XT derailleur comes with something called a Pro Set alignment block to set the gap, so I don't think that spacing is causing this particular problem.

    Thanks for your input.

    ChuckD

  23. #23
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    Monument, what chain are you running? It seems that most people with this problem are running SRAM chains on XT cranksets. I'm trying to figure out if trying a Shimano chain would solve the problem without having to go to an LX middle ring.

  24. #24
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    I seem to have the same problem with my Shimano 9 speed chain on my XT middle ring. Everythings pretty brand new. Otherwise the index shifting is nicely dialed in. I get the skip when heavily torquing with no shifting being attempted -- usually while motoring down an easy trail and suddenly coming upon some short, steep techy section. Expecting an LX ring to try next week. I've been making a point of staying in the smallest chainring more often to avoid occurances.

  25. #25
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    Quote Originally Posted by jcbikeski
    I seem to have the same problem with my Shimano 9 speed chain on my XT middle ring. Everythings pretty brand new. Otherwise the index shifting is nicely dialed in. I get the skip when heavily torquing with no shifting being attempted -- usually while motoring down an easy trail and suddenly coming upon some short, steep techy section. Expecting an LX ring to try next week. I've been making a point of staying in the smallest chainring more often to avoid occurances.
    Which chain are you running?
    Eat Food. Chop Wood. Ride Bike.

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