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  1. #1
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    Internal seat tube damage on a new carbon bike?

    I just purchased a new 2016 Niner RDO RKT (full carbon) mountain bike from Jensen USA. As I was inserting the 14" long seatpost, I hit some resistance around 6" in. So, I kinda worked it a little back and forth with a little force and it went in another 1", then stopped. Since the seatpost was still showing around 7" of length, I decided to pull out the seatpost and look down the seat tube. What I saw was this (see attached). Question: Did I encounter a "bubble" and shave off a layer or two of carbon fiber? Should I be concerned?

    Note: I ended up cutting off 3" of seatpost to obtain the length I wanted and I rode it 25 miles on a moderate singletrack without problems.
    Attached Thumbnails Attached Thumbnails Internal seat tube damage on a new carbon bike?-niner-seat-tube-view.jpg  


  2. #2
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    I purchased a Turner Sultan a few year ago and could not insert the seatpost more than 6-7". There were a few suspect welds that looked like they protruded into the tube. Called Turner bikes all ready for a warranty claim when I was explained even though it had a straight seat tube they only ream the tubes 150mm or so. I would contact Niner for their maximum insertion depth spec.

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    I've seen this on a few carbon frames. I've been told that if they were to ream deeper that the tool starts to chatter more and it ruins the upper part of the tube. That stuff you see in the looks like shavings from the reaming process to me. Let us know what niner says though

  4. #4
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    That's happening at 6" of insertion? IME, most seatposts have a minimum insertion of 100mm or 4". This would only allow you 2" max of adjustment which just doesn't seem right, to me. That, and looking at the carbon degradation, something's up. I wouldn't be "asking" Niner anything, I'd be demanding warranty replacement for their shitty manufacturing on that frame.

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    Quote Originally Posted by Oh My Sack! View Post
    This would only allow you 2" max of adjustment which just doesn't seem right, to me.
    It's not right. Period.

    I suspect a conversation with Niner would resolve your problem. You should not have to shorten your seat post to accommodate a frame flaw.
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  6. #6
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    Guys...thanks for your input. I contacted Niner a few hours ago. I'll post once I hear something back.

  7. #7
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    The damage looks like the seat post was scrapping the tube internally where it bends. If they have a maximum insertion length and you went past it, may be hard to warranty. Different companies have different lenience to what is a defect and what is a user error, good luck.

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    Thanks! However, no "maximum insertion length" was apparent. :/

    Still no answer from Niner on this after 2+ days. Hmmmm!

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    Quote Originally Posted by Edslittleworld View Post
    Thanks! However, no "maximum insertion length" was apparent. :/

    Still no answer from Niner on this after 2+ days. Hmmmm!
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  10. #10
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    People can take a situation like this (1) to the manufacturer, (2) to a public forum or (3) to both. IME whenever choosing the third option, it's best to go in this order: manufacturer first, public forum second.

    Best of luck dealing with Niner.
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  11. #11
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    Quote Originally Posted by Edslittleworld View Post
    Thanks! However, no "maximum insertion length" was apparent. :/
    Actually there was- it was when the seat post stopped moving easily.
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    Quote Originally Posted by TwoTone View Post
    Actually there was- it was when the seat post stopped moving easily.
    Now you're just being pedantic. I think he meant that if there wasn't a manufacturing problem in the first place there shouldn't have been an issue with inserting a seat post past 6". Looks like a warranty issue to me.

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    Quote Originally Posted by McKenzie View Post
    Now you're just being pedantic. I think he meant that if there wasn't a manufacturing problem in the first place there shouldn't have been an issue with inserting a seat post past 6". Looks like a warranty issue to me.
    We don't know how far down the seat tube the carbon separated. If it's at the bend then it might not be a warranty issue.

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    Quote Originally Posted by driver bob View Post
    We don't know how far down the seat tube the carbon separated. If it's at the bend then it might not be a warranty issue.
    The original post makes it sound like the separation happened at the 6" mark. Seems like 6" should be above the bend but I could be wrong.

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    Quote Originally Posted by McKenzie View Post
    Now you're just being pedantic. I think he meant that if there wasn't a manufacturing problem in the first place there shouldn't have been an issue with inserting a seat post past 6". Looks like a warranty issue to me.
    Thing is, on any frame if you feel resistance putting in a seat post, wouldn't you pull it out and look?

    Sorry if I'm somewhat amazed that someone takes the I'll push harder and twist it some before looking in the seat tube.
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    Quote Originally Posted by TwoTone View Post
    Thing is, on any frame if you feel resistance putting in a seat post, wouldn't you pull it out and look?

    Sorry if I'm somewhat amazed that someone takes the I'll push harder and twist it some before looking in the seat tube.
    I'm not claiming that pushing harder was the best decision to have made nor is it what I would have done. But if it is in fact a manufacturing defect then it's not like treating it gingerly is somehow going to solve the problem or cause the defect to disappear. I understand what you are saying I just think that mistakes are made and in the case of a manufacturing defect it matters very little one way or the other. Not everyone has the same frame of reference that you might have when it comes to working on bikes.

  17. #17
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    Finally, an answer from Niner.

    Quote Originally Posted by PeopleForScience View Post
    I've seen this on a few carbon frames. I've been told that if they were to ream deeper that the tool starts to chatter more and it ruins the upper part of the tube. That stuff you see in the looks like shavings from the reaming process to me. Let us know what niner says though
    That's pretty much the reply from Niner. It goes like this:

    "What you're seeing there is a pretty natural sight at the end of the bore depth in a seat tube. The can't really go any deeper due to the seat tube changing shape below that spot and the fact that at that extension the ream can get pretty wobbly, resulting in an inconsistent wall thickness at the top of the seat tube.

    We recommend no less then 4" of seat post insertion on all of our frames so being able to get into the frame 6" is within out tolerances and should give you no problems. Cutting a bit off of a seat post is fairly common in the bike world. Again, we just want to see 4" in the frame to avoid any seat tube damage."

    I guess I'm a bit surprised that a manufacturer would ream out carbon tubes. You'd think it could shave off resin or even a top layer of fiber. Hence, the scrap of carbon thread in the above picture. Hmmm!

  18. #18
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    "I'm not claiming that pushing harder was the best decision to have made nor is it what I would have done. But if it is in fact a manufacturing defect then it's not like treating it gingerly is somehow going to solve the problem or cause the defect to disappear. I understand what you are saying I just think that mistakes are made and in the case of a manufacturing defect it matters very little one way or the other. Not everyone has the same frame of reference that you might have when it comes to working on bikes."

    Well put!

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    Quote Originally Posted by Edslittleworld View Post
    That's pretty much the reply from Niner. It goes like this:

    "What you're seeing there is a pretty natural sight at the end of the bore depth in a seat tube. The can't really go any deeper due to the seat tube changing shape below that spot and the fact that at that extension the ream can get pretty wobbly, resulting in an inconsistent wall thickness at the top of the seat tube.

    We recommend no less then 4" of seat post insertion on all of our frames so being able to get into the frame 6" is within out tolerances and should give you no problems. Cutting a bit off of a seat post is fairly common in the bike world. Again, we just want to see 4" in the frame to avoid any seat tube damage."

    I guess I'm a bit surprised that a manufacturer would ream out carbon tubes. You'd think it could shave off resin or even a top layer of fiber. Hence, the scrap of carbon thread in the above picture. Hmmm!
    Glad they told you there is no need to worry! Definitely not a good feeling with a brand new expensive frame. Have fun riding that thing, my buddy has the same bike and loves it!

  20. #20
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    Quote Originally Posted by Edslittleworld View Post
    Question: Did I encounter a "bubble" and shave off a layer or two of carbon fiber? Should I be concerned?
    What did Niner say when you asked them about it?
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    The thing to keep in mind here is that carbon is insanely hard on machines. I'm told that it eats through cutting tools pretty quickly. I've talked to niner and other brands about this in the past and I have always been told that they leave a little extra resin in the seat tube specifically for reaming. Its unreasonable to think that a frame could come out of a mold with no post processing required, especially on tight tolerances like a seat tube or head tube. Also, carbon is black and the excess material in your seat tube is white-ish which coincidentally is the same color as the resin. I think that you are fine.
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    Quote Originally Posted by Edslittleworld View Post
    That's pretty much the reply from Niner. It goes like this:

    "What you're seeing there is a pretty natural sight at the end of the bore depth in a seat tube. The can't really go any deeper due to the seat tube changing shape below that spot and the fact that at that extension the ream can get pretty wobbly, resulting in an inconsistent wall thickness at the top of the seat tube."
    Huh?

    They make the shallow seat tube sound like some sort of industry norm. I have not seen this in any of the carbon bikes I have built up or worked on (Pivot, Yeti, Ibis, Turner, Giant and Cannondale).

  23. #23
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    Just curious but would this poor workmanship (that's what I'm calling it) negate the use of a typical dropper post due to insertion restriction? From my experience with droppers, it sounds like it would. Can you meet a typical 100mm minimum insertion and not have too much exposure out of the seat tube?

    One more thought is that on every carbon bike I have had, my inner seat tubes (with bends) are flawless and smooth. Perhaps Niner needs to get their manufacturing process dialed in a lot better.

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    Quote Originally Posted by Oh My Sack! View Post
    One more thought is that on every carbon bike I have had, my inner seat tubes (with bends) are flawless and smooth. Perhaps Niner needs to get their manufacturing process dialed in a lot better.
    +1.

    I will add- So far, IMHO from a customer service perspective, Niner has not handled this in an appropriate manner. They are dismissing an obvious issue with this frame.

    Not impressed.

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    Quote Originally Posted by 410sprint View Post
    +1.

    I will add- So far, IMHO from a customer service perspective, Niner has not handled this in an appropriate manner. They are dismissing an obvious issue with this frame.

    Not impressed.
    What's the obvious issue? Should they give him a new frame that is reamed to the same depth? What does that accomplish?
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  26. #26
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    Quote Originally Posted by Oh My Sack! View Post
    Just curious but would this poor workmanship (that's what I'm calling it) negate the use of a typical dropper post due to insertion restriction? From my experience with droppers, it sounds like it would. Can you meet a typical 100mm minimum insertion and not have too much exposure out of the seat tube?

    One more thought is that on every carbon bike I have had, my inner seat tubes (with bends) are flawless and smooth. Perhaps Niner needs to get their manufacturing process dialed in a lot better.
    Look at Niner's website- you aren't buying a new Niner if you want to run much of a dropper.

    The RDO has a 19'' seat tube for a large- then look at the crazy bent seat tube- I assume that is a limitation of the CVA suspension and trying to keep up with the short seat stay trend.

    Heck the RTK he bought has a 20'' seat tube for a large - that's ridiculous.
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    Quote Originally Posted by TwoTone View Post
    What's the obvious issue? Should they give him a new frame that is reamed to the same depth? What does that accomplish?
    If you don't see what I feel is an obvious issue in the picture provided by the OP, you and I can't have a productive discussion. Oh by the way, I never said anything about the depth of the seat tube.

  28. #28
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    On my Large RKT it's about 170mm from the top of the seat tube to the maximum insertion depth. The seatpost will not go beyond this point.

    Internal seat tube damage on a new carbon bike?-ninerseatinsert.jpg

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    Quote Originally Posted by 410sprint View Post
    If you don't see what I feel is an obvious issue in the picture provided by the OP, you and I can't have a productive discussion. Oh by the way, I never said anything about the depth of the seat tube.
    What's the obvious issue? Seriously. They told him that they ream the seat tubes, so where the reaming stops you're going to get some material left there.

    Now if they say we ream it to 6 inches and his only goes to 4 then yes I'd say there is an issue, but that little bit of material left in the tube is not an obvious issue.
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  30. #30
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    you got reamed.

  31. #31
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    Did you have to cut your seatpost, any? When I cut mine, it was obviously carbon fiber....but not like anything I've seen. I sure hope that my tubing cutter didn't put any stress cracks in the post.

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    Quote Originally Posted by Edslittleworld View Post
    Did you have to cut your seatpost, any? When I cut mine, it was obviously carbon fiber....but not like anything I've seen. I sure hope that my tubing cutter didn't put any stress cracks in the post.

    If you cut your carbon post with anything but a high tpi hacksaw then it is likely damaged.
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    Quote Originally Posted by PeopleForScience View Post
    If you cut your carbon post with anything but a high tpi hacksaw then it is likely damaged.
    How so? I always believed tube cutters to be more "gentle" as they don't leave jagged edges and are more even.

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    Who just rams it in there and twists? Always play "just the tip" first. Always.

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    Quote Originally Posted by Edslittleworld View Post
    How so? I always believed tube cutters to be more "gentle" as they don't leave jagged edges and are more even.
    I hope you don't mean a pipe cutter

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    Quote Originally Posted by Edslittleworld View Post
    How so? I always believed tube cutters to be more "gentle" as they don't leave jagged edges and are more even.
    Lets be clear, are you talking about something like this?

    Those cutters are designed to push material out of the way by crushing it at the blade edge. That is great for steel, okay for aluminum and terrible on carbon. Carbon cannot handle those crushing forces and it delaminates the base material. Essentially destroying it. A Hacksaw with a hit TPI and light pressure on the cutting stroke will cut cleanly and not destroy the base material. It is important that you do not put too much pressure on the cut or it will pull the base material apart and destroy it.
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    ^^That. You'll create havoc by trying to cut carbon with a pipe cutter. Get a proper saw or dremel wheel.

  38. #38
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    Pipe/tubing cutter is absolutely NG for CF, for reasons mentioned above. Use a very fine or abrasive saw blade. You can use an abrasive cut-off wheel but the danger there is overheating the carbon fiber.
    Do the math.

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    And don't breathe the dust, especially if ya use a wheel.

  40. #40
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    Quote Originally Posted by Edslittleworld View Post
    Did you have to cut your seatpost, any? When I cut mine, it was obviously carbon fiber....but not like anything I've seen. I sure hope that my tubing cutter didn't put any stress cracks in the post.
    Ok, everyone has publicly spanked you. Now you feel bad, but a lesson was learned.

    Let's talk seat post. Looking at where your seat post was cut...how's it look? Is it clean or showing any signs of fabric separation or delamination?
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  41. #41
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    Good info, guys. I just bought the same frame and ran into the same problem. Even using the RDO seatpost that Niner specs with their build. 25mil off the seatpost took care of that. A "max insertion depth" spec would be nice on Niner's site in this case...

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