Bad design or isolated incident?

Discussion in 'Cycling Equipment' started by Chris Zacho "Th, Feb 28, 2004.

  1. I have, or rather had, a quill type road stem with a removable face
    (Kalloy UNO). Here's what this stem looks like:

    http://www.chucksbikes.com/st002.htm

    This is identical to similar stems made by Profile Design and "Zoom" (A Performance brand name). I
    have owned it barely four years, when it failed last week. The top bolt pulled out (stripped).

    This did not occur while tightening the bolt, It failed during use. It was not over tightened. Nor
    had it been frequently loosened and re-tightened. I am not an overly heavy rider, I weigh 175 lbs
    soaking wet. I am not a particularly strong rider, but a tourist/recreational/endurance cyclist. And
    while I do like hills, I conquer them with low gears, not by standing and torqueing my bike into a
    pretzel. In any case, the failure occurred while riding casually (13 MPH) on level pavement. My
    handlebars just started twisting downwards, as the retaining cap came loose. I was able to finish
    the short ride safely, by riding carefully, bearing as little weight on the bars as possible.

    When I got home, I saw the top bolt had pulled out, stripping the hole. The fit of the bottom bolt
    was also sloppier than I felt it should be, like the hole was too big. Although this may have
    resulted from having to ride the bike with the top bolt kaput. The bolts were tight when I left, and
    there were the remains if five or six threads on the bolt. This was the same depth as the bottom
    bolt. Further examination of the stem and how it failed led me to believe that this _may_ have been
    due to a flaw in the design. Here is my reasoning:

    1. Unlike the MTB stems these are based upon, they only have two bolts, not four. Each bolt,
    therefore has to bear twice the load.

    2. They are parallel to the ground, not angled upwards, so the retaining cap must bear the entire
    load of the rider.

    3. The road rider is also leaned further forwards than on an MTB, so there is more weight for the
    stem to bear in the first place.

    As a result, this greater weight bourne by the handlebars is transmitted to the stem via the bottom
    portion of this cap. Actually, through the 5-6 aluminum threads the steel bolt was holding on to.
    This "force vector" would appear to be trying to "peel" the cap off the stem, in a downwards and
    forewards direction. In addition, every jolt from the road would force the steel bolts into the
    bottom of the threaded holes, gradually elongating them.

    By this action, the top bolt _would_ give away first, since it is bearing the greatest strain (both
    down and out, instead of just mostly down, like the bottom bolt). This is what eventually happened.
    Fortunately, it did not happen during a panic stop or on a steep decent.

    Anyway, this is my "barnyard engineering theory". If anyone here really IS an actual engineer, or
    has had the proper training in engineering or forensic science, and can confirm, or correct this
    theory, their input is welcome.

    More importantly, if anybody else has, or knows someone who has experienced failures like this on
    similar stems, I would definitely like to hear from them.

    "May you have the wind at your back. And a really low gear for the hills!"

    Chris Zacho ~ "Your Friendly Neighborhood Wheelman"

    Chris'Z Corner http://www.geocities.com/czcorner
     
    Tags:


  2. Jim Beam

    Jim Beam Guest

    all the documentation i've seen for alloy stems, [when the piece comes in the full retail box at any
    rate] has a specific warning about replacement every few years - annually for some of the light
    weight racing stuff.

    bottom line is that alloy fatigues. it's not /if/, it's /when/. four years of use may not be as good
    as the life exhibited by some of the wonderful old cinelli's for example, but for a regular cyclist,
    four years is not an outrageously low life either, especially for a low end component like this.

    there's not necessarily anything wrong with the two bolt design. if it worries you, get a
    replacement that has more, but the key to safe cycling is regular inspection, service & replacement.
    same goes for handlebars and every other component come to that.

    Chris Zacho The Wheelman wrote:
    > I have, or rather had, a quill type road stem with a removable face (Kalloy UNO). Here's what this
    > stem looks like:
    >
    > http://www.chucksbikes.com/st002.htm
    >
    > This is identical to similar stems made by Profile Design and "Zoom" (A Performance brand name). I
    > have owned it barely four years, when it failed last week. The top bolt pulled out (stripped).
    >
    > This did not occur while tightening the bolt, It failed during use. It was not over tightened. Nor
    > had it been frequently loosened and re-tightened. I am not an overly heavy rider, I weigh 175 lbs
    > soaking wet. I am not a particularly strong rider, but a tourist/recreational/endurance cyclist.
    > And while I do like hills, I conquer them with low gears, not by standing and torqueing my bike
    > into a pretzel. In any case, the failure occurred while riding casually (13 MPH) on level
    > pavement. My handlebars just started twisting downwards, as the retaining cap came loose. I was
    > able to finish the short ride safely, by riding carefully, bearing as little weight on the bars as
    > possible.
    >
    > When I got home, I saw the top bolt had pulled out, stripping the hole. The fit of the bottom bolt
    > was also sloppier than I felt it should be, like the hole was too big. Although this may have
    > resulted from having to ride the bike with the top bolt kaput. The bolts were tight when I left,
    > and there were the remains if five or six threads on the bolt. This was the same depth as the
    > bottom bolt. Further examination of the stem and how it failed led me to believe that this _may_
    > have been due to a flaw in the design. Here is my reasoning:
    >
    > 1. Unlike the MTB stems these are based upon, they only have two bolts, not four. Each bolt,
    > therefore has to bear twice the load.
    >
    > 2. They are parallel to the ground, not angled upwards, so the retaining cap must bear the entire
    > load of the rider.
    >
    > 3. The road rider is also leaned further forwards than on an MTB, so there is more weight for the
    > stem to bear in the first place.
    >
    > As a result, this greater weight bourne by the handlebars is transmitted to the stem via the
    > bottom portion of this cap. Actually, through the 5-6 aluminum threads the steel bolt was holding
    > on to. This "force vector" would appear to be trying to "peel" the cap off the stem, in a
    > downwards and forewards direction. In addition, every jolt from the road would force the steel
    > bolts into the bottom of the threaded holes, gradually elongating them.
    >
    > By this action, the top bolt _would_ give away first, since it is bearing the greatest strain
    > (both down and out, instead of just mostly down, like the bottom bolt). This is what eventually
    > happened. Fortunately, it did not happen during a panic stop or on a steep decent.
    >
    > Anyway, this is my "barnyard engineering theory". If anyone here really IS an actual engineer, or
    > has had the proper training in engineering or forensic science, and can confirm, or correct this
    > theory, their input is welcome.
    >
    > More importantly, if anybody else has, or knows someone who has experienced failures like this on
    > similar stems, I would definitely like to hear from them.
    >
    > "May you have the wind at your back. And a really low gear for the hills!"
    >
    > Chris Zacho ~ "Your Friendly Neighborhood Wheelman"
    >
    > Chris'Z Corner http://www.geocities.com/czcorner
     
  3. Frank Knox

    Frank Knox Guest

    "jim beam" <[email protected]> wrote in message
    news:M%[email protected]...
    > all the documentation i've seen for alloy stems, [when the piece comes in the full retail box at
    > any rate] has a specific warning about replacement every few years - annually for some of the
    > light weight racing stuff.
    >
    > bottom line is that alloy fatigues. it's not /if/, it's /when/. four years of use may not be as
    > good as the life exhibited by some of the wonderful old cinelli's for example, but for a regular
    > cyclist, four years is not an outrageously low life either, especially for a low end component
    > like this.
    >
    > there's not necessarily anything wrong with the two bolt design. if it worries you, get a
    > replacement that has more, but the key to safe cycling is regular inspection, service &
    > replacement. same goes for handlebars and every other component come to that.
    >
    >
    Was there a warning label on the stem when you bought it, informing you of failure after 4 years?

    This is a critical component on which our lives sometimes depends. In the event of a failure causing
    a tragedy, I doubt a plaintiff's attorney would take the same position as you. This is an excellent
    reason for buying a stem from a U.S. maker who is within easy reach of the generous juries in our
    courts. U.S. makers are financially motivated to keep us safe. A little fear can be a good thing...
     
  4. From: [email protected] (jim=A0beam)

    >all the documentation i've seen for alloy stems, [when the piece comes in the full retail box at
    >any rate] has a specific warning about replacement every few years - annually for some of the light
    >weight racing stuff.
    >
    >bottom line is that alloy fatigues. it's not /if/, it's /when/. four years of use may not be as
    >good as the life exhibited by some of the wonderful old Cinelli's for example, but for a regular
    >cyclist, four years is not an outrageously low life either, especially for a low end component
    >like this.
    >
    >there's not necessarily anything wrong with the two bolt design. if it worries you, get a
    >replacement that has more, but the key to safe cycling is regular inspection, service &
    >replacement. same goes for handlebars and every other component come to that.

    A better designed stem is the way I'm going, I just wanted to know if the failure is consistent with
    this front mount design. This is the first road stem with a removable plate I have had. I won't make
    the same design mistake again! I do regularly inspect my equipment before every ride. As I mentioned
    in my original post, the bolts were tight when I started.

    I do like the removable face plate, though, especially with my laced leather handlebar wraps. And I
    think I found a better designed stem. Ironically, it too, is made by Cinelli. They call it the
    "Frog". Kinda dorky looking, BUT the plate is on the top, not the front. So the stem, not the
    faceplate bears the weight. It also has three bolts.

    From the reviews I've read, it's virtually indestructible. These coming from "hard" riders.

    "May you have the wind at your back. And a really low gear for the hills!"

    Chris Zacho ~ "Your Friendly Neighborhood Wheelman"

    Chris'Z Corner http://www.geocities.com/czcorner
     
  5. S. Anderson

    S. Anderson Guest

    "Chris Zacho "The Wheelman"" <[email protected]> wrote in message
    news:[email protected]...

    >A better designed stem is the way I'm going, I just wanted to know if the failure is consistent
    >with this front mount design.

    First off, and with absolutely no offence intended, I'm not sure we're qualified to decide which
    stem is "better designed". You can choose a different stem and if you're more comfortable with it,
    that's fine. But I'm not sure you're going to get a "better design" without some thoughtful
    calculations. There's probably nothing wrong with a 2-bolt front faceplate design. The execution may
    be somewhat questionable in this case, and that can range from quality of construction to quality of
    materials to quality of design. I assure you though, a 2-bolt design such as that can be made to
    take considerably more abuse than a cyclist can dish out.

    Design is always a balance of cost, lightness and durability. Components can be designed to be very
    light, but may not be very durable. With your particular situation, my guess is the component is
    actually defective. I've never seen a front faceplate stem fail in that way. I don't think (I could
    be wrong..) that there are boatloads of failures. That leads me to believe that you particular
    situation may be somewhat unique.

    Cheers,

    Scott..
     
  6. S. Anderson

    S. Anderson Guest

    "Frank Knox" <[email protected]> wrote in message
    news:[email protected]...
    > Was there a warning label on the stem when you bought it, informing you of failure after 4 years?
    >
    > This is a critical component on which our lives sometimes depends. In the event of a failure
    > causing a tragedy, I doubt a plaintiff's attorney would take the same position as you. This is an
    > excellent reason for buying a stem from a U.S. maker who is within easy reach of the generous
    > juries in our courts. U.S. makers are financially motivated to keep us safe. A little fear can
    be
    > a good thing...

    It can also kill entire industries because of frivolous lawsuits. Ask Bell helmets, an American
    company (the last I think, that produces helmets..) nearly sued out of existence by what I think are
    safe to call frivolous lawsuits. Or the light aircraft industry. It's incredibly myopic, but all too
    common, to think that any failure of any kind that can result in an injury or death must result in a
    lawsuit for negligence. Now in this case, I think there may be a problem that could result in a
    successful lawsuit had injury occurred.

    A question here: can you not sue a company that sells products in the U.S. but is based in a foreign
    country? I'm certain you must be able to. For instance, if your Hyundai explodes one day, I'm
    certain you can sue Hyundai for damages, correct?

    Cheers,

    Scott..
     
  7. Chris Zacho "The Wheelman <[email protected]> wrote:

    > A better designed stem is the way I'm going, I just wanted to know if the failure is consistent
    > with this front mount design. This is the first road stem with a removable plate I have had. I
    > won't make the same design mistake again! I do regularly inspect my equipment before every ride.
    > As I mentioned in my original post, the bolts were tight when I started.

    > I do like the removable face plate, though, especially with my laced leather handlebar wraps. And
    > I think I found a better designed stem. Ironically, it too, is made by Cinelli. They call it the
    > "Frog". Kinda dorky looking, BUT the plate is on the top, not the front. So the stem, not the
    > faceplate bears the weight. It also has three bolts.

    > From the reviews I've read, it's virtually indestructible. These coming from "hard" riders.

    Most stems are hard to destroy - any stem with a moderate failure rate is gonna get recalled, given
    the consequences of sudden stem failure. This does happen (e.g. Profile recalled some stems a few
    years ago). Probably nearly all of the people who have your two-bolt stem have not broken it. That
    is small comfort, of course, it just means that reviews aren't telling you much.

    I'm not sure the Frog design is significantly different. I suspect that much of the stress on stem
    clamp bolts comes from repeated loading and unloading, especially when climbing and pulling on the
    bars. There, pulling up on one side will stress the Frog clamp much like any other. Without an
    engineering analysis, we don't really know if one is better, or even if 4-bolt clamps are really
    stronger than 2-bolt. (Tip: on multi bolt clamp stems, it's probably more important than usual to
    get the bolts to the same torque.)

    The type of failure you had - threads stripping out of the aluminum body of the stem - could have
    happened in many stems, even the non-open-face quill type like old Cinellis. Whether it happens
    probably has to do with strength of the material, precision of machining, and luck. If you want a
    stem with threads that won't strip, get a steel stem. If you want an open-face steel stem (with a
    solid reputation as a bonus) get a Salsa.
     
  8. Frank Knox

    Frank Knox Guest

    "S. Anderson" <[email protected]> wrote in message
    news:[email protected]...
    > "Frank Knox" <[email protected]> wrote in message
    > news:[email protected]...
    > > Was there a warning label on the stem when you bought it, informing you
    of
    > > failure after 4 years?
    > >
    > > This is a critical component on which our lives sometimes depends. In
    the
    > > event of a failure causing a tragedy, I doubt a plaintiff's attorney
    would
    > > take the same position as you. This is an excellent reason for buying a stem from a U.S. maker
    > > who is within easy reach of the generous juries in our courts. U.S. makers are financially
    > > motivated to keep us safe. A little fear
    can
    > be
    > > a good thing...
    >
    > It can also kill entire industries because of frivolous lawsuits. Ask
    Bell
    > helmets, an American company (the last I think, that produces helmets..) nearly sued out of
    > existence by what I think are safe to call frivolous lawsuits. Or the light aircraft industry.
    > It's incredibly myopic, but
    all
    > too common, to think that any failure of any kind that can result in an injury or death must
    > result in a lawsuit for negligence. Now in this
    case,
    > I think there may be a problem that could result in a successful lawsuit
    had
    > injury occurred.
    >
    > A question here: can you not sue a company that sells products in the
    U.S.
    > but is based in a foreign country? I'm certain you must be able to. For instance, if your Hyundai
    > explodes one day, I'm certain you can sue
    Hyundai
    > for damages, correct?
    >
    > Cheers,
    >
    > Scott..
    >
    Good question. Car makers generally import their own and do business here. Don't bike parts makers
    usually fill an order for an importer and just mail it to them? I'll bet it's easier to collect
    damages from a domestic producer, but I really don't know.

    I agree that frivolous lawsuits are frustrating and expensive for all of us. Folks need to be
    responsible for their own actions, but that includes manufacturers too. We trust them with
    our safety.
     
  9. Frank Knox

    Frank Knox Guest

    "Chris Zacho "The Wheelman"" <[email protected]> wrote in message
    news:[email protected]et...
    From: [email protected] (jim beam)

    >all the documentation i've seen for alloy stems, [when the piece comes in the full retail box at
    >any rate] has a specific warning about replacement every few years - annually for some of the light
    >weight racing stuff.
    >
    >bottom line is that alloy fatigues. it's not /if/, it's /when/. four years of use may not be as
    >good as the life exhibited by some of the wonderful old Cinelli's for example, but for a regular
    >cyclist, four years is not an outrageously low life either, especially for a low end component
    >like this.
    >
    >there's not necessarily anything wrong with the two bolt design. if it worries you, get a
    >replacement that has more, but the key to safe cycling is regular inspection, service &
    >replacement. same goes for handlebars and every other component come to that.

    A better designed stem is the way I'm going, I just wanted to know if the failure is consistent with
    this front mount design. This is the first road stem with a removable plate I have had. I won't make
    the same design mistake again! I do regularly inspect my equipment before every ride. As I mentioned
    in my original post, the bolts were tight when I started.

    I do like the removable face plate, though, especially with my laced leather handlebar wraps. And I
    think I found a better designed stem. Ironically, it too, is made by Cinelli. They call it the
    "Frog". Kinda dorky looking, BUT the plate is on the top, not the front. So the stem, not the
    faceplate bears the weight. It also has three bolts.

    From the reviews I've read, it's virtually indestructible. These coming from "hard" riders.

    "May you have the wind at your back. And a really low gear for the hills!"

    Chris Zacho ~ "Your Friendly Neighborhood Wheelman"

    Chris'Z Corner http://www.geocities.com/czcorner

    My Motus stem failed. Fortunately I was not hurt. I bought a Salsa with a removable face plate and
    have had no problems at all. I don't need to check the stem each ride (or ever). They shape part of
    the face plate similar to fit into a slot in the stem face. This greatly lessons stress on the bolts
    I suppose.
     
  10. Jay Beattie

    Jay Beattie Guest

    "Benjamin Weiner" <[email protected]> wrote in message
    news:[email protected]...
    > Chris Zacho "The Wheelman <[email protected]> wrote:

    <snip>

    >The type of failure you had - threads stripping out of the
    aluminum
    > body of the stem - could have happened in many stems, even the non-open-face quill type like old
    > Cinellis.

    Actually, the Cinelli 1As had a steel bolt threaded into a steel sleeve. I have a number of these,
    some almost 30 years old -- and the oldest ones were raced for many years. This was a great, long-
    lived product Not all that convenient, but very durable. -- Jay Beattie.
     
  11. Jay Beattie

    Jay Beattie Guest

    "Frank Knox" <[email protected]> wrote in message
    news:[email protected]...
    >
    > "S. Anderson" <[email protected]> wrote in message
    > news:[email protected]...
    > > "Frank Knox" <[email protected]> wrote in
    message
    > > news:[email protected]...
    > > > Was there a warning label on the stem when you bought it,
    informing you
    > of
    > > > failure after 4 years?
    > > >
    > > > This is a critical component on which our lives sometimes
    depends. In
    > the
    > > > event of a failure causing a tragedy, I doubt a plaintiff's
    attorney
    > would
    > > > take the same position as you. This is an excellent reason for buying a stem from a U.S.
    maker who is
    > > > within easy reach of the generous juries in our courts. U.S. makers are financially motivated
    > > > to keep us safe. A
    little fear
    > can
    > > be
    > > > a good thing...
    > >
    > > It can also kill entire industries because of frivolous
    lawsuits. Ask
    > Bell
    > > helmets, an American company (the last I think, that produces
    helmets..)
    > > nearly sued out of existence by what I think are safe to call
    frivolous
    > > lawsuits. Or the light aircraft industry. It's incredibly
    myopic, but
    > all
    > > too common, to think that any failure of any kind that can
    result in an
    > > injury or death must result in a lawsuit for negligence. Now
    in this
    > case,
    > > I think there may be a problem that could result in a
    successful lawsuit
    > had
    > > injury occurred.
    > >
    > > A question here: can you not sue a company that sells
    products in the
    > U.S.
    > > but is based in a foreign country? I'm certain you must be
    able to. For
    > > instance, if your Hyundai explodes one day, I'm certain you
    can sue
    > Hyundai
    > > for damages, correct?
    > >
    > > Cheers,
    > >
    > > Scott..
    > >
    > Good question. Car makers generally import their own and do
    business here.
    > Don't bike parts makers usually fill an order for an importer
    and just mail
    > it to them? I'll bet it's easier to collect damages from a
    domestic
    > producer, but I really don't know.

    Most automobile manufacturers have American distribution companies, e.g. Honda America, American
    Kawasaki, etc. These companies get sued all of the time and have registered agents in every state.
    Getting jurisdiction over a smal bicycle OEM is a different matter. Depending on their distribution
    network, it may be impossible to establish jurisdiction in the United States -- or at least in your
    state. Also, the small Chinese and Korean OEMs often have sketchy insurance. And if you get a
    judgment against one of these OEMs, it is unlikely that you will be able to collect it. This is how
    the domestic seller and its insurer gets screwed -- the insurer for the mom-and-pop LBS ends up
    paying the tab and then has to chase the OEM around for indemnity.

    > I agree that frivolous lawsuits are frustrating and expensive
    for all of us.
    > Folks need to be responsible for their own actions, but that
    includes
    > manufacturers too. We trust them with our safety.

    Frivolous lawsuits are the ones where the plaintiff injures himself while attempting to shave with a
    gas lawnmower, etc. When you get into parts that break while "just riding along" (for real, and not
    just claimed), then you have plenty to talk about. I have defended stem and bar claims, some were
    frivolous and some were not. The "were not" claims involved knock-off ultralight OEM parts spec'd
    from a catalogue with no manufacturing or design oversight by the domestic seller. Much of the re-
    branded OEM stuff we see now is produced in accordance with designs created in the United States and
    with process oversight by the domestic seller. I would not worry about that stuff, especially since
    it is such a large part of the market now. -- Jay Beattie.
     
  12. Peter Cole

    Peter Cole Guest

    "Jay Beattie" <[email protected]> wrote in message
    news:[email protected]...
    >
    > "Benjamin Weiner" <[email protected]> wrote in message news:[email protected]...

    > >The type of failure you had - threads stripping out of the
    > aluminum
    > > body of the stem - could have happened in many stems, even the non-open-face quill type like old
    > > Cinellis.
    >
    > Actually, the Cinelli 1As had a steel bolt threaded into a steel sleeve. I have a number of these,
    > some almost 30 years old -- and the oldest ones were raced for many years. This was a great, long-
    > lived product Not all that convenient, but very durable. -- Jay Beattie.

    The failures that get my attention are the ones that can cause a crash. But from that point of
    view, minor things like a chain skip or cleat release can take you down. The extreme failures I've
    had (no crashes so far, knock on wood): stem, axle, chain, seat rail, and frame failures, all have
    been "fail-soft". I do worry about handlebar, crank spindle, crank pedal eye, and any kind of fork
    failure though.
     
  13. Andres Muro

    Andres Muro Guest

    Hey Chris:

    I haven't had this problem, but know that alum screws are a screw up. I stripped several threads by
    not being careful. I striped my first screw on a cinelli 1A stem that I was trying to tighten to a
    26.00 handlebar many years ago. I was ignorant about stem compatibility back then. I would replace
    the alum screw with a SS one.

    Andres

    [email protected] (Chris Zacho "The Wheelman") wrote in message news:<[email protected]
    3174.bay.webtv.net>...
    > I have, or rather had, a quill type road stem with a removable face (Kalloy UNO). Here's what this
    > stem looks like:
    >
    > http://www.chucksbikes.com/st002.htm
    >
    > This is identical to similar stems made by Profile Design and "Zoom" (A Performance brand name). I
    > have owned it barely four years, when it failed last week. The top bolt pulled out (stripped).
    >
    > This did not occur while tightening the bolt, It failed during use. It was not over tightened. Nor
    > had it been frequently loosened and re-tightened. I am not an overly heavy rider, I weigh 175 lbs
    > soaking wet. I am not a particularly strong rider, but a tourist/recreational/endurance cyclist.
    > And while I do like hills, I conquer them with low gears, not by standing and torqueing my bike
    > into a pretzel. In any case, the failure occurred while riding casually (13 MPH) on level
    > pavement. My handlebars just started twisting downwards, as the retaining cap came loose. I was
    > able to finish the short ride safely, by riding carefully, bearing as little weight on the bars as
    > possible.
    >
    > When I got home, I saw the top bolt had pulled out, stripping the hole. The fit of the bottom bolt
    > was also sloppier than I felt it should be, like the hole was too big. Although this may have
    > resulted from having to ride the bike with the top bolt kaput. The bolts were tight when I left,
    > and there were the remains if five or six threads on the bolt. This was the same depth as the
    > bottom bolt. Further examination of the stem and how it failed led me to believe that this _may_
    > have been due to a flaw in the design. Here is my reasoning:
    >
    > 1. Unlike the MTB stems these are based upon, they only have two bolts, not four. Each bolt,
    > therefore has to bear twice the load.
    >
    > 2. They are parallel to the ground, not angled upwards, so the retaining cap must bear the entire
    > load of the rider.
    >
    > 3. The road rider is also leaned further forwards than on an MTB, so there is more weight for the
    > stem to bear in the first place.
    >
    > As a result, this greater weight bourne by the handlebars is transmitted to the stem via the
    > bottom portion of this cap. Actually, through the 5-6 aluminum threads the steel bolt was holding
    > on to. This "force vector" would appear to be trying to "peel" the cap off the stem, in a
    > downwards and forewards direction. In addition, every jolt from the road would force the steel
    > bolts into the bottom of the threaded holes, gradually elongating them.
    >
    > By this action, the top bolt _would_ give away first, since it is bearing the greatest strain
    > (both down and out, instead of just mostly down, like the bottom bolt). This is what eventually
    > happened. Fortunately, it did not happen during a panic stop or on a steep decent.
    >
    > Anyway, this is my "barnyard engineering theory". If anyone here really IS an actual engineer, or
    > has had the proper training in engineering or forensic science, and can confirm, or correct this
    > theory, their input is welcome.
    >
    > More importantly, if anybody else has, or knows someone who has experienced failures like this on
    > similar stems, I would definitely like to hear from them.
    >
    > "May you have the wind at your back. And a really low gear for the hills!"
    >
    > Chris Zacho ~ "Your Friendly Neighborhood Wheelman"
    >
    > Chris'Z Corner http://www.geocities.com/czcorner
     
  14. JMatt

    JMatt Guest

    I had a KORE 3 that did exactly the same thing, although it stripped during a crash.

    j.
     
  15. Jay Beattie <[email protected]> wrote:

    > Actually, the Cinelli 1As had a steel bolt threaded into a steel sleeve. I have a number of these,
    > some almost 30 years old -- and the oldest ones were raced for many years. This was a great, long-
    > lived product Not all that convenient, but very durable. --

    Thanks for the correction, Jay. I was thinking of many quill stems which probably resembled the
    Cinellis, but had threads in aluminum. These rarely failed, either - rare failures do happen
    but don't necessarily indicate a design flaw. OTOH, quill stems of that type usually used a
    single M8 clamp bolt - open face stems tend to use two M6 bolts, which probably means less
    depth in the threads.
     
  16. Jeff Wills

    Jeff Wills Guest

    "S. Anderson" <[email protected]> wrote in message news:<[email protected]>...
    > "Chris Zacho "The Wheelman"" <[email protected]> wrote in message news:[email protected]
    > 3178.bay.webtv.net...
    >
    > >A better designed stem is the way I'm going, I just wanted to know if the failure is consistent
    > >with this front mount design.
    >
    > First off, and with absolutely no offence intended, I'm not sure we're qualified to decide which
    > stem is "better designed". You can choose a different stem and if you're more comfortable with it,
    > that's fine. But I'm not sure you're going to get a "better design" without some thoughtful
    > calculations. There's probably nothing wrong with a 2-bolt front faceplate design. The execution
    > may be somewhat questionable in this case, and that can range from quality of construction to
    > quality of materials to quality of design. I assure you though, a 2-bolt design such as that can
    > be made to take considerably more abuse than a cyclist can dish out.
    >

    Hmmm... I'm not a designer, but I've been around for quite a piece, and I was chatting with a bike-
    parts building friend of mine about 1-bolt vs. 2-bolt faceplates recently. (Pat Franz of Terracycle
    if you have to know.)

    With a 1-bolt stem, the handlebar clamp contracts relatively evenly all the way around the
    handlebar. This puts a fairly equal grip all the way around the bar.

    By contrast, the front and back plates of a 2-bolt stem are more rigid and squish the handlebar
    between them, kind of like this: ->(O)<- ovalizing the handlebar slightly. It seems to me that this
    could damage the handlebar more easily than the 1-bolt stem, assuming equal resistance to handlebar
    rotation. *I* think that the 2-bolt clamps are inferior to 1-bolt clamps.

    BTW: Chris's original assertion that "Zoom" parts are a Performance brand is incorrect. Zoom is a
    brand used by Hsin Lung parts in the U.S.- they began to establish this brand in 1991 or 1992 or
    thereabouts. Take a look at http://www.hlcorp.com.tw/ .

    Jeff
     
  17. Jean

    Jean Guest

    With respect to the problem cited by the original poster:

    I have a Dimension version of the stem (same as the Zoom and Profile stems). Based on your posting,
    I took a very close-up look at my stem. In particular, I looked at the exposed threads (ie, the
    threads between the faceplate and the stem body) on the top bolt.

    I found some metal filings which looked to me like the shredded bits of metal you get when you cross-
    thread a bolt and ream the threads. Since I have not cross-threaded the bolt, I'm "guessing" that
    the aluminum in the stem is pretty soft and normal torqueing of the bolt can shred the threads.

    So in answer to your original question, I vote for "bad design".

    Jean
     
  18. Jeff Wills

    Jeff Wills Guest

    "David L. Johnson" <[email protected]> wrote in message
    news:<[email protected]>... <snip>
    >
    > I disagree. Were it that the only effect on the bars was the clamping, you might have a point, but
    > even then the roundness of a 1-bolt system would have to be perfect to give you an advantage
    > there. But the big difference, for road bars, is the damage you do installing them in the stem.
    > All those scratches are stress risers. Two-bolt stems avoid that completely.

    Good point. However, I learned to install handlebars without scratching them 25 years ago, so *for
    me* it's a moot point.

    Jeff
     
  19. Onefred

    Onefred Guest

    salsa make a nice two bolt front plate type quill stem. it's called the stiff upper lip, or s.u.l.
    it's steel so you won't need to worry about it it's not super light but it certainly is not a heavy
    piece. it's light enough

    dave

    "Chris Zacho "The Wheelman"" <[email protected]> wrote in message news:[email protected]
    3174.bay.webtv.net...
    > I have, or rather had, a quill type road stem with a removable face (Kalloy UNO). Here's what this
    > stem looks like:
    >
    > http://www.chucksbikes.com/st002.htm
    >
    > This is identical to similar stems made by Profile Design and "Zoom" (A Performance brand name). I
    > have owned it barely four years, when it failed last week. The top bolt pulled out (stripped).
    >
    > This did not occur while tightening the bolt, It failed during use. It was not over tightened. Nor
    > had it been frequently loosened and re-tightened. I am not an overly heavy rider, I weigh 175 lbs
    > soaking wet. I am not a particularly strong rider, but a tourist/recreational/endurance cyclist.
    > And while I do like hills, I conquer them with low gears, not by standing and torqueing my bike
    > into a pretzel. In any case, the failure occurred while riding casually (13 MPH) on level
    > pavement. My handlebars just started twisting downwards, as the retaining cap came loose. I was
    > able to finish the short ride safely, by riding carefully, bearing as little weight on the bars as
    > possible.
    >
    > When I got home, I saw the top bolt had pulled out, stripping the hole. The fit of the bottom bolt
    > was also sloppier than I felt it should be, like the hole was too big. Although this may have
    > resulted from having to ride the bike with the top bolt kaput. The bolts were tight when I left,
    > and there were the remains if five or six threads on the bolt. This was the same depth as the
    > bottom bolt. Further examination of the stem and how it failed led me to believe that this _may_
    > have been due to a flaw in the design. Here is my reasoning:
    >
    > 1. Unlike the MTB stems these are based upon, they only have two bolts, not four. Each bolt,
    > therefore has to bear twice the load.
    >
    > 2. They are parallel to the ground, not angled upwards, so the retaining cap must bear the entire
    > load of the rider.
    >
    > 3. The road rider is also leaned further forwards than on an MTB, so there is more weight for the
    > stem to bear in the first place.
    >
    > As a result, this greater weight bourne by the handlebars is transmitted to the stem via the
    > bottom portion of this cap. Actually, through the 5-6 aluminum threads the steel bolt was holding
    > on to. This "force vector" would appear to be trying to "peel" the cap off the stem, in a
    > downwards and forewards direction. In addition, every jolt from the road would force the steel
    > bolts into the bottom of the threaded holes, gradually elongating them.
    >
    > By this action, the top bolt _would_ give away first, since it is bearing the greatest strain
    > (both down and out, instead of just mostly down, like the bottom bolt). This is what eventually
    > happened. Fortunately, it did not happen during a panic stop or on a steep decent.
    >
    > Anyway, this is my "barnyard engineering theory". If anyone here really IS an actual engineer, or
    > has had the proper training in engineering or forensic science, and can confirm, or correct this
    > theory, their input is welcome.
    >
    > More importantly, if anybody else has, or knows someone who has experienced failures like this on
    > similar stems, I would definitely like to hear from them.
    >
    > "May you have the wind at your back. And a really low gear for the hills!"
    >
    > Chris Zacho ~ "Your Friendly Neighborhood Wheelman"
    >
    > Chris'Z Corner http://www.geocities.com/czcorner
     
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