Question on developing split in carbon steerer tube

Discussion in 'Cycling Equipment' started by Kovie, Jun 24, 2004.

  1. Kovie

    Kovie Guest

    Last year I purchased a Forte Axis Pro Carbon road fork from Performance
    Bike as part of a combo that also included a Cane Creek S2 headset, a Forte
    Pro stem, and carbon spacers. I used it to build up a new Ti road bike. I
    actually had a local bike shop press the headset and cut and install the
    fork, as I didn't have the tools or expertise to do this myself. I gave them
    the instructions that came with these components, including the recommended
    torque settings. The fork, I have to add, has a carbon steerer tube as well.

    So far I've ridden over 700 miles on this bike and it's been just great.
    Recently, however, I noticed that a slight amount of play had developed in
    the headset, so I released the stem- steerer tube bolts and plug bolt in
    order to remove the stem. When I did this, I noticed that the carbon steerer
    tube had developed a split or fracture along the top inch or so, at
    precisely the same place where the metal shim was split. As I have no reason
    to believe that the bike shop overtorqued the stem bolts, it appears that
    there's some sort of defect in the carbon steerer tube, and I'm hesitant to
    put any more miles on the bike for fear of a catastrophic failure.

    Is this common, and what could have caused this? Am I correct in assuming
    that it's unwise to ride this fork, and that it needs to be replaced right
    away?

    --
    Kovie
    [email protected]zen
     
    Tags:


  2. A Muzi

    A Muzi Guest

    Kovie wrote:

    > Last year I purchased a Forte Axis Pro Carbon road fork from Performance
    > Bike as part of a combo that also included a Cane Creek S2 headset, a Forte
    > Pro stem, and carbon spacers. I used it to build up a new Ti road bike. I
    > actually had a local bike shop press the headset and cut and install the
    > fork, as I didn't have the tools or expertise to do this myself. I gave them
    > the instructions that came with these components, including the recommended
    > torque settings. The fork, I have to add, has a carbon steerer tube as well.
    >
    > So far I've ridden over 700 miles on this bike and it's been just great.
    > Recently, however, I noticed that a slight amount of play had developed in
    > the headset, so I released the stem- steerer tube bolts and plug bolt in
    > order to remove the stem. When I did this, I noticed that the carbon steerer
    > tube had developed a split or fracture along the top inch or so, at
    > precisely the same place where the metal shim was split. As I have no reason
    > to believe that the bike shop overtorqued the stem bolts, it appears that
    > there's some sort of defect in the carbon steerer tube, and I'm hesitant to
    > put any more miles on the bike for fear of a catastrophic failure.
    >
    > Is this common, and what could have caused this? Am I correct in assuming
    > that it's unwise to ride this fork, and that it needs to be replaced right
    > away?
    >

    Yes, it is common and Yes, it would be prudent to retire
    that fork.

    --
    Andrew Muzi
    www.yellowjersey.org
    Open every day since 1 April, 1971
     
  3. Kovie-<< Is this common, and what could have caused this? Am I correct in
    assuming
    that it's unwise to ride this fork, and that it needs to be replaced right
    away? >><BR><BR>


    Not common, don't ride it.

    Peter Chisholm
    Vecchio's Bicicletteria
    1833 Pearl St.
    Boulder, CO, 80302
    (303)440-3535
    http://www.vecchios.com
    "Ruote convenzionali costruite eccezionalmente bene"
     
  4. On 25 Jun 2004 12:41:06 GMT, [email protected] (Qui si parla
    Campagnolo ) wrote:

    >Kovie-<< Is this common, and what could have caused this? Am I correct in
    >assuming
    >that it's unwise to ride this fork, and that it needs to be replaced right
    >away? >><BR><BR>
    >
    >
    >Not common, don't ride it.
    >
    >Peter Chisholm
    >Vecchio's Bicicletteria
    >1833 Pearl St.
    >Boulder, CO, 80302
    >(303)440-3535
    >http://www.vecchios.com
    >"Ruote convenzionali costruite eccezionalmente bene"


    Dear Andrew and Peter,

    So the crack seems to be either common or uncommon?

    Hamlet: Ay, madam, it is common.

    Queen: If it be,
    Why seems it so particular with thee?

    Hamlet: Seems, madam? nay it is, I know not "seems."
    'Tis not alone my nastily split metal shim, good mother,
    Nor customary cracked carbon steerer tube of solemn black.
    'Tis that wicked bastard Claudius, who hath hired
    Sinful slaveys who doth over-torque all that they touch,
    More often in Madison than in Boulder.

    Queen: Madison? Boulder? O, my son runs mad,
    And babbles stone-mad of unknown places!

    Hamlet: I say we will have no moe carbon steerers.
    A horse! A horse! My kingdom for a horse!

    Bill S.
     
  5. Kovie

    Kovie Guest

    I like the way you slipped some Richard III in there at the end. But didn't
    you mean bike instead of horse? ;-)

    --
    Kovie
    [email protected]zen


    <[email protected]> wrote in message
    news:[email protected]
    > On 25 Jun 2004 12:41:06 GMT, [email protected] (Qui si parla
    > Campagnolo ) wrote:
    >
    > >Kovie-<< Is this common, and what could have caused this? Am I correct in
    > >assuming
    > >that it's unwise to ride this fork, and that it needs to be replaced

    right
    > >away? >><BR><BR>
    > >
    > >
    > >Not common, don't ride it.
    > >
    > >Peter Chisholm
    > >Vecchio's Bicicletteria
    > >1833 Pearl St.
    > >Boulder, CO, 80302
    > >(303)440-3535
    > >http://www.vecchios.com
    > >"Ruote convenzionali costruite eccezionalmente bene"

    >
    > Dear Andrew and Peter,
    >
    > So the crack seems to be either common or uncommon?
    >
    > Hamlet: Ay, madam, it is common.
    >
    > Queen: If it be,
    > Why seems it so particular with thee?
    >
    > Hamlet: Seems, madam? nay it is, I know not "seems."
    > 'Tis not alone my nastily split metal shim, good mother,
    > Nor customary cracked carbon steerer tube of solemn black.
    > 'Tis that wicked bastard Claudius, who hath hired
    > Sinful slaveys who doth over-torque all that they touch,
    > More often in Madison than in Boulder.
    >
    > Queen: Madison? Boulder? O, my son runs mad,
    > And babbles stone-mad of unknown places!
    >
    > Hamlet: I say we will have no moe carbon steerers.
    > A horse! A horse! My kingdom for a horse!
    >
    > Bill S.
     
  6. Kovie

    Kovie Guest

    So does this sound like it's due to overtorqueing, to using a split shim, or
    to a defect in the carbon steerer?

    --
    Kovie
    [email protected]zen


    "Qui si parla Campagnolo " <[email protected]> wrote in message
    news:[email protected]
    > Kovie-<< Is this common, and what could have caused this? Am I correct in
    > assuming
    > that it's unwise to ride this fork, and that it needs to be replaced right
    > away? >><BR><BR>
    >
    >
    > Not common, don't ride it.
    >
    > Peter Chisholm
    > Vecchio's Bicicletteria
    > 1833 Pearl St.
    > Boulder, CO, 80302
    > (303)440-3535
    > http://www.vecchios.com
    > "Ruote convenzionali costruite eccezionalmente bene"
     
  7. Weisse Luft

    Weisse Luft Guest

    The split might have been from improper installation or improper
    trimming. Either way, its not a good sign.

    Carbon steerer tubes with minimal bias filaments are stiff in bending
    and tension but lack significant hoop strength, or more precisely,
    compressive modulus. When initially tightened, the stem clamp's pressure
    "grabbed" the surface of the tube with enough "grip" to prevent sliding
    and additional torque on the bolts caused the gap to close,
    concentrating the stress on the clamp split.

    This is avoided with a bias cut as on Ritchey stems and others.

    Its possible to use a True Temper Alpha Q style insert in lieu of the
    star nut to restore strength to the steerer and prevent further damage.
    Since the limited bias fibers in the steerer have been compromised, I
    would not recommend repair if the split extends below the insert. Be
    sure to sand the ID of the steerer tube for the full length of the
    insert and coat both surfaces with slow expoy. Tape the insert/steerer
    tube well to prevent epoxy leaking when you invert the stem to allow
    bubbles to escape before the epoxy cures.

    The compromised strength is in torsion. It would be prudent to limit
    spacers to 5mm below the stem. likewise, discontinue use if the
    torsional stiffness changes.



    --
     
  8. On Fri, 25 Jun 2004 19:13:56 GMT, "Kovie"
    <[email protected]> wrote:

    >I like the way you slipped some Richard III in there at the end. But didn't
    >you mean bike instead of horse? ;-)


    Dear Kovie,

    Well, no . . .

    When the wind is southerly, I know a hawk from a handsaw
    And roared but for a horse to replace a bike

    What's in a name? That which we call a bike
    By any other word would smell as sweet,
    Were it but greased before installation.

    Blow, winds, and crack your carbon steerers!

    Hopalong Cassidy
     
  9. A Muzi

    A Muzi Guest

    >>Kovie-<< Is this common, and what could have caused
    this? Am I correct in
    >>assuming
    >>that it's unwise to ride this fork, and that it needs to be replaced right
    >>away? >><BR><BR>


    > On 25 Jun 2004 12:41:06 GMT, [email protected] (Qui si parla
    > Campagnolo ) wrote:
    >>Not common, don't ride it.


    [email protected] wrote:
    > Dear Andrew and Peter,
    > So the crack seems to be either common or uncommon?

    -snip-

    Semantics.
    My reply: When you do that, this is the result. Do not ride it.
    Peter's reply: Not everyone wrecks their forks. Do not ride it.

    I think we are in agreement, actually.
    --
    Andrew Muzi
    www.yellowjersey.org
    Open every day since 1 April, 1971
     
  10. carl-<< So the crack seems to be either common or uncommon? >><BR><BR>

    Cracks in carbon steerers in my experience is unusual. I would not ride the
    bike regardless.

    Peter Chisholm
    Vecchio's Bicicletteria
    1833 Pearl St.
    Boulder, CO, 80302
    (303)440-3535
    http://www.vecchios.com
    "Ruote convenzionali costruite eccezionalmente bene"
     
  11. Kovie

    Kovie Guest

    Thanks to all for your comments and tips. I took the fork back to
    Performance today and they were nice enough to install a replacement fork
    under warranty. The mechanic said that this could have been caused by the
    shim's split being aligned with the stem's split. When I got the stem I
    actually inserted the shim with the split opposite the stem's split, which
    seemed intuitive to me, but the shop that cut and installed the fork
    reversed it so that they aligned. I figured that this was how it was
    supposed to work so I didn't question them. It also occured to me that
    torque readings don't necessary apply to carbon. Is that the case?

    --
    Kovie
    [email protected]zen
     
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