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  1. #1
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    Rear derailleur FAIL! Help!

    So here's the deal. I bought a Pivot Mach 429 Carbon in May after riding a Specialized Epic for 11 years and beating the hell out of it and it never begged for mercy. On my 3rd ride out with a small group, we ride through a small depression, more like a dry puddle, and as the rear suspension compresses - KABOOM! Rear derailleur ends up in rear wheel, breaks spokes, explodes the XTR carbon arm and scratches the rear triangle at the dropout. After spending much more than I budgeted I was not happy but LBS and Pivot make it right and swap out the rear triangle, replace the XTR derailleur and replace spokes and off I go. Things seem pretty good but it keeps phantom shifting so I take it in. LBS sees that derailleur isn't parallel to cassette and swaps out the drop out and still not great. The owner of the shop, who recommended the bike to me, tinkers with it and seems to get it all right. I ride off and about 6 rides in today, I come over a small rise and maybe get my fat ass 2 inches in the air and as the suspension compresses - KABOOM! Same exact thing happens again!

    So, what gives? I'm 44 years old and weigh 230 pounds and wonder again, as I did a few months ago when it first happened, if I am too heavy for the DT Swiss XR400's (manufacturer says 110kg max weight, ~243 pounds)? My LBS assures me I am not but as you might imagine, I'm losing faith in them. Do you think the wheel is deforming and the spokes expand and catch the rear derailleur or does the chain slacken and the derailleur shift over into the wheel? I have called the LBS and Pivot and neither were too happy to hear from me. I know the saying, "I was just riding along...", but this is BS. I have treated this thing like a baby, no falls, never lean it against anything when stored or transporting. There were no scratches on it before today. Any thoughts? Some have said the chain may be too short but why would Pivot ship a bike with a chain that is too short?
    Last edited by spicywings; 10-03-2013 at 07:04 PM.

  2. #2
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    Quote Originally Posted by spicywings View Post
    So, what gives?
    You need a new mechanic, seriously.

  3. #3
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    Weird and a total bummer you've experienced the same issue twice. You may be onto something regarding the flex, but it may have more to do with the spokes than rims. Assuming you went with the 32 spoke option, maybe rebuild the rear wheel with DT Compatition or even Champion spokes; maybe Sapim butted Strongs. Good luck.

  4. #4
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    I've been mountain biking for over 20 years and I never heard of a failure like yours. I've bent and broke derailleurs. and hangers from sticks. I did have a hanger fail with no obvious inciting factor. I can't imagine your wheel deforming so much it would contact the derailleur. Could it be a too short chain imploding the derailleur? I would cross post on the drive train forum.


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  5. #5
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    I think I figger'd it out. I read up on the XTR Shadow Plus - probably should have done that beforehand since it is a relatively new item and was certainly to me! Seems that it is in the OFF position on my bike. Apparently this makes it easier to remove the rear wheel and also tune the derailleur. Only problem is, by leaving it off you lose its advantage which is that it reduces chain slap by keeping the cage toward the rear of the bike. So it seems that it was never switched ON. Could it be that when I happened to just compress the suspension enough and fate decided, the chain got sucked in on itself or could it be that the derailleur swung over and got caught? Seems that way to me because each time it broke the spokes.
    Last edited by spicywings; 10-03-2013 at 07:08 PM.

  6. #6
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    Pivot Mach 429 Carbon FAIL! Help!

    Quote Originally Posted by spicywings View Post
    I think I figger'd it out. I read up on the XTR Shadow Plus - probably should have done that beforehand, although it would have been nice for the shop to tell me about it in the first place since it is a relatively new item and was certainly to me! Seems that it is in the OFF position on my bike. Apparently this makes it easier to remove the rear wheel and also tune the derailleur. Only problem is, by leaving it off you lose its advantage which is that it reduces chain slap by keeping the cage toward the rear of the bike. So it seems that they never switched it ON and never told me about it. When I happened to just compress the suspension enough and fate decided, the chain got sucked in on itself or could it be that the derailleur swung over and got caught? Seems that way to me because each time it broke the spokes.
    That's not the answer. Until 18 months ago we all happily ran regular rear derailleurs without rear triangles and wheels imploding.

    I would check the length of the chain before doing anything else, as was suggested above, and make sure the limit screws are set right.

  7. #7
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    I checked the chain length on the stand and it was right. Unfortunately, the derailleur was ripped off the hanger so I am sure the adjustment is all wrong at this point.

  8. #8
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    Recently I went from a 39/26 to 36/24 crank and it would not shift right. The chain was too loose. I took out a couple of links and it was too tight. I cursed my stupidity and took it to the LBS. Same problem - too tight. I had to replace the medium cage derailleur with a long cage.


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  9. #9
    11 is one louder than 10
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    It's not your weight.

    It's likely one of a few things.

    1. Chain too short. And when the suspension is compressing in the big-big combo - it's snapping off the rear derailleur

    2. A "Combo" platter. You say you are ghost shifting, on a full suspension bike that likely because the cable housing is too short. When the suspension is compressing it pulls the rear derailleur cable - causing ghost shifting - problem 1.

    3. Combo part two - your rear derailleur was improperly adjusted on the bike and the lower limit screw is allowing (or it is being forced by that tight cable and the suspension compressing) that rear derailleur to jump into the rear spokes - causing the rest of the issues.

    It's one of the above two. It's not the frame, it's not the rear wheel.

    I lean toward the second combo platter as you mentioned ghost shifting when the suspension compresses. If that is the case, unfortunately it's whomever built the bike up fault.

    Pivot did you a real solid replacing that rear end. Even if it had been shipped with a cable too short, it's only partially pivots fault. If you are paying a shop to build the bike up, it's on them.

    It's a great bike, and it's a great bike for big guys. I'm 190-210 lbs at any given time. Most solid full suspension I've ever owned. I've owned a lot.
    "The thing is, Bob, it's not that I'm lazy, it's that I just don't care."

  10. #10
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    Bent L-screw contribution - does this make sense????

    Quote Originally Posted by Green Giant View Post
    It's not your weight.

    It's likely one of a few things.

    1. Chain too short. And when the suspension is compressing in the big-big combo - it's snapping off the rear derailleur

    2. A "Combo" platter. You say you are ghost shifting, on a full suspension bike that likely because the cable housing is too short. When the suspension is compressing it pulls the rear derailleur cable - causing ghost shifting - problem 1.

    3. Combo part two - your rear derailleur was improperly adjusted on the bike and the lower limit screw is allowing (or it is being forced by that tight cable and the suspension compressing) that rear derailleur to jump into the rear spokes - causing the rest of the issues.

    It's one of the above two. It's not the frame, it's not the rear wheel.

    I lean toward the second combo platter as you mentioned ghost shifting when the suspension compresses. If that is the case, unfortunately it's whomever built the bike up fault.

    Pivot did you a real solid replacing that rear end. Even if it had been shipped with a cable too short, it's only partially pivots fault. If you are paying a shop to build the bike up, it's on them.

    It's a great bike, and it's a great bike for big guys. I'm 190-210 lbs at any given time. Most solid full suspension I've ever owned. I've owned a lot.
    I think you are on to something with the adjustment screw. Look at these pictures I put together of the rear end after the first incident (on left) and second incident (on right - I have to hold it bc it was ripped off). The L adjustment screw is all the way in on both and you can appreciate that it is bent in both views if you look closely (circled). In the 3rd photo you can see how the L screw is bent and was rubbing on the derailleur. Also, even though it may not have anything to do with it, the Shadow Plus is in the OFF position both times. Since my last bike had 11 year old XT components on it I had no idea about this feature. Go ahead and kill me for not knowing about it.

    As someone somewhere mentioned, as the DW Link suspension compresses the drivetrain lengthens and if the chain is too short (even if just by a bit) AND the L-screw is adjusted too far in, then couldn't it pull the cage over and BOOM?
    Attached Thumbnails Attached Thumbnails Rear derailleur FAIL! Help!-sidebyside1.jpg  

    Rear derailleur FAIL! Help!-sidebyside2.jpg  

    Rear derailleur FAIL! Help!-bentlscrew.jpg  

    Last edited by spicywings; 10-03-2013 at 07:11 PM.

  11. #11
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    It has ZERO to do with the clutch switch. You're barking up the wrong tree with that line of thought, as others have mentioned.
    www.seanhannity.com <=not what you think it is.

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  12. #12
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    Quote Originally Posted by juan_speeder View Post
    It has ZERO to do with the clutch switch. You're barking up the wrong tree with that line of thought, as others have mentioned.
    Agreed.
    Last edited by spicywings; 10-03-2013 at 07:13 PM.

  13. #13
    11 is one louder than 10
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    Something forced that r.der past it's limit. Likely the cable housing length, possibly the chain length.

    It's one of those two things. It's not the frame, not the clutch, and not the rear wheel.
    "The thing is, Bob, it's not that I'm lazy, it's that I just don't care."

  14. #14
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    Here's a pic of the housing after the first incidentRear derailleur FAIL! Help!-imageuploadedbytapatalk1380812430.239714.jpg. Looks ok to me, right?

  15. #15
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    Quote Originally Posted by spicywings View Post
    Here's a pic of the housing after the first incidentClick image for larger version. 

Name:	ImageUploadedByTapatalk1380812430.239714.jpg 
Views:	168 
Size:	178.9 KB 
ID:	836432. Looks ok to me, right?
    Can't tell. The more critical housing is the piece between the front and rear triangles.

    Only way to tell what is happening is to completely deflate your shock, put your bike in the big ring and big cog. Compress the suspension. See what your rear der does.

    Of course, after it's rebuilt.
    "The thing is, Bob, it's not that I'm lazy, it's that I just don't care."

  16. #16
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    Way more smart people here than me... but thought I would throw something in for the ghost shifting... I / we (friends) just went through a spate of ghost shifting...turns out its was the simplest thing (of course after I checked everything else)... back wheel was not torqued down tight enough (and I mean tight) thus was shifting a bit in position and thus it was semi / ghost shifting a bit under torque / twist etc.

    Funny thing his was the same problem...an neither of remove the rear wheels often...just worked loose.

    Sorry for your troubles.

  17. #17
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    You should consider changing the title of this thread and the other one you started to "Local Shop FAIL".

    Quote Originally Posted by spicywings View Post
    ...I'm losing faith that the shop is familiar with this setup and that these two incidents are ENTIRELY on them.

  18. #18
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    Not fair as they're a good shop that stands by their work. Sometimes bad things happen to good guys. I just want it fixed so I can get back out on the bike.
    Last edited by spicywings; 10-03-2013 at 07:19 PM.

  19. #19
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    Spending a mint on a mountain bike has nothing to do with your local bike shop issues. But it's good to know the Pivot Mach 429 Carbon is not a FAIL as your titles on the multiple threads proclaim.

  20. #20
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    Good points, so allow me to clarify.

    1. The bike - Pivot Mach 429 Carbon - is still the best bike I've ever ridden.
    2. The shop is a good shop and they stand by their work and assure me that they will do what they can again to make this right.
    3. The original title was unfair to Pivot so I changed it.
    4. I have been jaded by a case of buyer's remorse and having these problems.
    5. I look forward to the day when I can get back on the bike, feel comfortable that I can ride as hard as I want and not worry that the rear end is gonna lock up on me and toss me into a potentially dangerous situation. Call me lucky that I never had this happen before and now unlucky that it happened twice on the first 6 rides on my new bike. Unfortunately, for a little while after this is resolved instead of finding peace and enjoyment when I'm out on the trails, I'm gonna be hesitant until I get comfortable on this new bike. Not exactly what I intended when I spent this much money.

  21. #21
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    Sounds like too short chain - I had just the same happen to me.
    You should test the chain length on big - big combination and cycle the suspension even if you would not normally ride on this gearing.

  22. #22
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    Craig just take my niner air 9 c singlespeed and don't worry about rear derailleur!

    Quote Originally Posted by spicywings View Post
    Good points, so allow me to clarify.

    1. The bike - Pivot Mach 429 Carbon - is still the best bike I've ever ridden.
    2. The shop is a good shop and they stand by their work and assure me that they will do what they can again to make this right.
    3. The original title was unfair to Pivot so I changed it.
    4. I have been jaded by a case of buyer's remorse and having these problems.
    5. I look forward to the day when I can get back on the bike, feel comfortable that I can ride as hard as I want and not worry that the rear end is gonna lock up on me and toss me into a potentially dangerous situation. Call me lucky that I never had this happen before and now unlucky that it happened twice on the first 6 rides on my new bike. Unfortunately, for a little while after this is resolved instead of finding peace and enjoyment when I'm out on the trails, I'm gonna be hesitant until I get comfortable on this new bike. Not exactly what I intended when I spent this much money.

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