Is this frame safe for casual riding?- Mtbr.com
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  1. #1
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    Is this frame safe for casual riding?

    I volunteer at a bike collective, and someone donated a Cannondale Caffeine F29.
    The whole bike is in good shape, except for a repair at the junction below the seat clamp on both sides of the notch.
    The frame is an X-large, and I can see how a big guy could cause it to crack.
    You can see from the crack on the drive side that the crack has permeated through the repair weld.
    The lump on the left side is just the weld that hasn't been filed/sanded down.
    We decided to keep the bike for shop functions as it'd be a liability to donate or sell it to someone.
    But for casual street riding at functions and group rides without any hard riding, does it seem ok?




  2. #2
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    First off I am not any kind of structural engineer. I have had a 2004 Stumpjumper fsr break in the same basic place because I didn't have my seatpost inserted far enough into the frame. I took it to a welder and he bead welded the crack and told me it was stronger than before it cracked. Rode the bike hard for two more years before selling the bike.
    Just my 2....

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  3. #3
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    Quote Originally Posted by jbourge View Post
    First off I am not any kind of structural engineer. I have had a 2004 Stumpjumper fsr break in the same basic place because I didn't have my seatpost inserted far enough into the frame. I took it to a welder and he bead welded the crack and told me it was stronger than before it cracked. Rode the bike hard for two more years before selling the bike.
    Just my 2....

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    Maybe, but since it looks like that weld is cracked, I'd go with no.

    Also, what are the spidery marks all over the area? Also not an engineer, so don't know if those indicate further stress and/or weakness.

  4. #4
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    Ok, some other folks that know a lot more than me will come along and answer. But, that's not going to stop me from answering as well.

    What is the worse that would happen if that breaks? It looks like it is just around the top of the seattube where it extends above the junction of the top tube and seat stays. So if it cracks all the ways around, as long as there is plenty of seat post within the seat tube, the post still isn't going anywhere. The post and the collar will hold it all together. However, it could allow the seat post to rotate so I wouldn't be doing anything *too crazy* on it.

    And I would also very carefully check the whole frame.

    EDIT: it would also would be able to rise up so I'd be sure you have plenty of post in the seat tube and I'd stick to roads and very smooth trails.
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  5. #5
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    Semi-professional frame breaker here. If you're going to ride a broken frame, that's about the most harmless place to have it happen. Fairly low risk and yes I think it's reasonable to tool around an urban area with casual riding.

    I'd personally want to weld up that crack before putting it into service, for longevity. If you really want to bolt it in there you can drill the seattube and seatpost below the TT/seat stay junction and run a bolt through there. Even if the top gives way the bolt will keep everything in place.

    Pretty sure this is a steel frame? You can have that crappy weld ground down and re-welded. Or you can weld right over the top of that crack. Either way you're putting a bandaid on a bad situation but if it will live out it's days doing casual cruises, should be just fine.
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  6. #6
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    Thanks for the info guys.
    To answer a few questions...
    Those weird spidery marks, we think, are stains from stuff falling on it while being stored. We've had to scrape off what looks like wallpaper paste or drywall mud from spots on the frame.
    Kinda hard to believe someone would store a once-killer bike and spill stuff all over it.
    And the frame is aluminum.
    Here's a pic of the bike after I started cleaning it up. Once we get the weld fixed, I'm going to completely rebuild and tune it, and give that raw aluminum frame the sweet, sweet polish that it deserves.
    Then I thought, "This bike cost a good chunk of change when it was new (I think 2006 or 2007), and now someone didn't want it anymore and just gave it away.


  7. #7
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    I think, if that's it in the crack dept. , that it's safe to use in a light duty role.

  8. #8
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    I know someone who has cracked at least three F29s at the TT/ST. He keeps getting it replaced under warranty.

  9. #9
    Hitching a ride
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    Get it re-welded by someone who knows what they're doing.

  10. #10
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    Not worth the money to re weld but you might want to get a nice thick hose clamp and run it up nice and tight. Might be enough support to keep that from spreading. Also I would drill a hole at the end of the crack to keep it from propagating.
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  11. #11
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    Needs professional TIG weld repair. Line inner tube with soda can sheet, polish and go ride casually.

    This was originally caused by jumbo rider, overextending exposed seatpost insertion.


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  12. #12
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    I'd ride it with a long seatpost inserted deeply into the seat tube.

  13. #13
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    Quote Originally Posted by eshew View Post
    Not worth the money to re weld but you might want to get a nice thick hose clamp and run it up nice and tight. Might be enough support to keep that from spreading. Also I would drill a hole at the end of the crack to keep it from propagating.
    It did have a hose clamp over the crack when we got the bike, although we didn't notice it at first.

    Some bikes we get in have been MacGuyvered by people adding racks and weird stuff to it.

    But mostly we were "Why would someone donate a cool bike like this? Hmmm.....waitaminute...let's see under that hose clamp. Awwwwww."

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