peugeot cracked frame

Discussion in 'Cycling Equipment' started by davec, Feb 28, 2006.

  1. davec

    davec Guest

    Hello, I have an older Alummium frame Peugeot.There is a small crack
    near the top of the seat tube.It happened when a taller rider raised
    the seat to high.How much of a problem is this? Can I just lower the
    seat back down and ride or are there safety issues? What about repair
    if necessary?

    thanks dave
     
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  2. Werehatrack

    Werehatrack Guest

    On 28 Feb 2006 14:40:11 -0800, "davec" <[email protected]> wrote:

    >Hello, I have an older Aluminium frame Peugeot.There is a small crack
    >near the top of the seat tube. It happened when a taller rider raised
    >the seat too high. How much of a problem is this?


    Large, if the crack is below the top tube. Smaller and possibly easy
    to deal with if it's above the top tube. The top of the seat tube is
    one of the most heavily stressed parts of the frame; no crack there
    should be ignored.

    >Can I just lower the
    >seat back down and ride or are there safety issues?


    If the crack is above the top tube, is there enough of the seat tube
    present that you could simply shorten it to remove the damaged area,
    and then relocate the seatpost clamp? Depending on the crack's
    location and orientation, it might even be possible to simply
    stop-drill the crack and ride on, though I doubt that this will be the
    case.

    If the crack is below the top tube, or if it's above the top tube but
    not in a location where removing the damaged end is an option, things
    are less hopeful. If the seatpost is long enough, a failure would
    probably not be of the type in which the rider is suddenly and
    unexpectedly dumped from the bike at speed, but the potential for both
    additional damage to the frame (rendering it completely unrepairable)
    and hazard to the rider is more than I would be comfortable with.
    Given that you are aware that the failure was causes by misuse,
    there's no warranty issue involved. Your choices essentially come
    down to repair or replacement.

    >What about repair
    >if necessary?


    This is something that would have to be addressed by a frame shop.
    It's possible that locating a replacement frame and transferring your
    components would be a more economical solution that trying to weld the
    crack, particularly if the frame is bonded instead of welded. If the
    frame is bonded, there are probably more repair options than if it's
    welded.
    --
    Typoes are a feature, not a bug.
    Some gardening required to reply via email.
    Words processed in a facility that contains nuts.
     
  3. Werehatrack <[email protected]> writes:

    >On 28 Feb 2006 14:40:11 -0800, "davec" <[email protected]> wrote:


    >>Hello, I have an older Aluminium frame Peugeot.There is a small crack
    >>near the top of the seat tube. It happened when a taller rider raised
    >>the seat too high. How much of a problem is this?


    >If the crack is above the top tube, is there enough of the seat tube
    >present that you could simply shorten it to remove the damaged area,
    >and then relocate the seatpost clamp? Depending on the crack's
    >location and orientation, it might even be possible to simply
    >stop-drill the crack and ride on, though I doubt that this will be the
    >case.


    Sorry, but if you are talking about a crack in the top tube being a
    problem then I think this statement is false. The top tube is the
    least-stressed tube in a bicycle today. That's why it was always a 1"
    tube on vintage bikes, whereas seat tube and downtube were 1 1/8. The
    top tube is under compression. This is not a severe load. Dents in
    the top tube - bad ones - often produce no structural consequences.

    The downtube is the most heavily stressed tube, since your whole body
    weight is trying to rip the downtube out from the bottom bracket and
    from the lower head lug. The seat tube takes a lot of flexion from
    pedaling and so cracks in the seat tube (especially near the bottom
    bracket area) can easily grow.

    If the crack is in the seat lug, if any, then I think you are in
    trouble because the crack will likely grow larger. Depending on the
    location you should probably either attempt to sand or file smooth the
    insides of the crack to remove stress risers and prevent it from
    growing larger, or just ditch the frameset. If you keep the frame it
    want be good to get a well-fitting 400mm post in an attempt to spread
    the torque from your body over a wider area of the seat tube.

    - Don Gillies
    San Diego, CA
     
  4. Werehatrack <[email protected]> writes:

    >On 28 Feb 2006 14:40:11 -0800, "davec" <[email protected]> wrote:


    >>Hello, I have an older Aluminium frame Peugeot. There is a small
    >>crack near the top of the seat tube. It happened when a taller
    >>rider raised the seat too high. How much of a problem is this?


    >If the crack is above the top tube, is there enough of the seat tube
    >present that you could simply shorten it to remove the damaged area,
    >and then relocate the seatpost clamp? Depending on the crack's
    >location and orientation, it might even be possible to simply
    >stop-drill the crack and ride on, though I doubt that this will be
    >the
    >case.


    Sorry, but if you are talking about a crack in the top tube being a
    problem then I think this statement is false. The top tube is the
    least-stressed tube in a bicycle today. That's why it was always a 1"
    tube on vintage bikes, whereas seat tube and downtube were 1 1/8, and
    on many high-tech bikes the downtube is 2x larger than any other tube.
    The top tube is under compression. This is not a severe load. Dents
    in the top tube - bad ones - often produce no structural consequences.

    The downtube is the most heavily stressed tube, since your whole body
    weight is trying to rip the downtube out from the bottom bracket and
    from the lower head tube/lug. The seat tube takes a lot of flexion
    from pedaling in the bb area and so cracks in the seat tube
    (especially near the bottom bracket area) can easily grow.

    If the crack is in the seat lug, above the top tube, then it may not
    grow larger. Depending on the location you should probably either
    attempt to sand or file smooth the insides of the crack to remove
    stress risers and prevent it from growing larger, or just ditch the
    frameset. If you keep the frame I would at least get a well-fitting
    400mm post in an attempt to spread the torque from your body over a
    wider area of the seat tube.

    - Don Gillies
    San Diego, CA
     
  5. Werehatrack

    Werehatrack Guest

    On 28 Feb 2006 18:46:11 -0800, [email protected] (Donald Gillies)
    wrote:

    >Werehatrack <[email protected]> writes:
    >
    >>On 28 Feb 2006 14:40:11 -0800, "davec" <[email protected]> wrote:

    >
    >>>Hello, I have an older Aluminium frame Peugeot. There is a small
    >>>crack near the top of the seat tube. It happened when a taller
    >>>rider raised the seat too high. How much of a problem is this?

    >
    >>If the crack is above the top tube, is there enough of the seat tube
    >>present that you could simply shorten it to remove the damaged area,
    >>and then relocate the seatpost clamp? Depending on the crack's
    >>location and orientation, it might even be possible to simply
    >>stop-drill the crack and ride on, though I doubt that this will be
    >>the
    >>case.

    >
    >Sorry, but if you are talking about a crack in the top tube


    The OP stated that the crack is in the seat tube.

    >being a
    >problem then I think this statement is false. The top tube is the
    >least-stressed tube in a bicycle today.


    The top tube is not under discussion.

    > That's why it was always a 1"
    >tube on vintage bikes, whereas seat tube and downtube were 1 1/8, and
    >on many high-tech bikes the downtube is 2x larger than any other tube.
    >The top tube is under compression. This is not a severe load. Dents
    >in the top tube - bad ones - often produce no structural consequences.


    It's a crack, not a dent, and it's in the seat tube.

    >The downtube is the most heavily stressed tube, since your whole body
    >weight is trying to rip the downtube out from the bottom bracket and
    >from the lower head tube/lug. The seat tube takes a lot of flexion
    >from pedaling in the bb area and so cracks in the seat tube
    >(especially near the bottom bracket area) can easily grow.


    Which is exactly what is under discussion.

    >If the crack is in the seat lug, above the top tube, then it may not
    >grow larger.


    Stated location was in the tube. The frame is aluminum, so lugs are
    unlikely; even bonded frames typically used internally-fitted sleeve
    joints.

    > Depending on the location you should probably either
    >attempt to sand or file smooth the insides of the crack to remove
    >stress risers and prevent it from growing larger, or just ditch the
    >frameset. If you keep the frame I would at least get a well-fitting
    >400mm post in an attempt to spread the torque from your body over a
    >wider area of the seat tube.


    A crack in aluminum in an area subject to flexing will grow if not
    stop-drilled (or the equivalent). Filing the edges will do nothing
    unless the propagating end of the crack is opened to a smooth margin;
    that's what a stop-drill accomplishes. If the crack is below the top
    tube, I question the wisdom of trying to sleeve it with a long post.
    --
    Typoes are a feature, not a bug.
    Some gardening required to reply via email.
    Words processed in a facility that contains nuts.
     
  6. jim beam

    jim beam Guest

    davec wrote:
    > Hello, I have an older Alummium frame Peugeot.There is a small crack
    > near the top of the seat tube.It happened when a taller rider raised
    > the seat to high.How much of a problem is this? Can I just lower the
    > seat back down and ride or are there safety issues? What about repair
    > if necessary?
    >
    > thanks dave
    >

    cracking is a serious issue - it can lead to sudden catastrophic
    failure, and personal injury.

    if you can post a pic here, it would be handy. if not, discontinue use
    as the prudent action. repair of aluminum frames is uneconomic as they
    require heat treatment.
     
  7. Peter Cole

    Peter Cole Guest

    davec wrote:
    > Hello, I have an older Alummium frame Peugeot.There is a small crack
    > near the top of the seat tube.It happened when a taller rider raised
    > the seat to high.How much of a problem is this? Can I just lower the
    > seat back down and ride or are there safety issues? What about repair
    > if necessary?


    If the crack is above the top tube, there's probably no danger from
    catastrophic failure. If the crack is small enough, drill 2 small holes,
    one at each end of the crack. That's about the only practical repair. It
    might help to use the longest seatpost you can find.
     
  8. davec wrote:
    > Hello, I have an older Alummium frame Peugeot.There is a small crack
    > near the top of the seat tube.It happened when a taller rider raised
    > the seat to high.How much of a problem is this? Can I just lower the
    > seat back down and ride or are there safety issues? What about repair
    > if necessary?
    >
    > thanks dave
    >

    Is the crack vertical or horizontal?
    EJ in NJ
     
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