Bulge on Carbon Steerer

JS said:

I was trying to put a different sized stem on my girlfriend's bike and I
couldn't remove it without giving it a few hits with a mallot. Even after a
few hard hits, I finally abandoned the idea after I realized a bulge in the
steerer tube where the expansion nut was situated. I was worried about
snapping the steerer tube and causing further damage. It appears the person
who put together her bike overtightened the bolt to the expansion nut.

Seeing as to how difficult it was to remove the stem and the bulge on the
steerer, I recommended she get a new fork altogether as I'm worried about
her safety and some catastrophic incident occurring. So far, no incidents
have occurred while she's ridden/raced on the bike. She's even had some
wrench at a shop tell her that "it's probably okay" without looking at it.
As much as I keep telling her to replace that fork, she still refuses to do
it. Someone tell me I'm not being unreasonable as to the danger of riding
on a fork that appears to be compromised.

Thanks,
John

relationship management is your problem. as far as the technical
question is concerned, yes, the bulge is potenially a serious problem
that could lead to fork failure. the fork needs to be condemned &
replaced asap.

On Thu, 15 Sep 2005 04:16:45 GMT, "JS" <[email hidden]>

Quoted message said:

... Someone tell me I'm not being unreasonable as to the danger of riding
on a fork that appears to be compromised.

Without seeing it, making the call is difficult...but I'll throw this
into the discussion for starters, assuming there is a discussion...

If the bulge is at or above the top of the stem's clamp, I do not
personally think it is likely to cause a catastrophic failure, as the
clamp is grabbing the tube at a point where it is presumably still
sound. However, without knowing the mode by which the failure might
propagate, this is an opinion unsupported by any facts.

If the bulge is within the clamp of the stem, and if the steerer is
sound below the bulge, then my guess is that the chances are good that
the steerer will remain together as long as the stresses on it are
light. The gotcha, in my estimation, involves what happens in a hard
bump when leaning forward, or in a hard stop situation, where the
weight transfer forward and/or the impluse loading of the stem goes
up. I have to wonder about the possibility that the tube may deform
and allow the stem to come loose.

Second observation: ISTR that there have been reports of corrosion at
the interface between metal and cabon fiber; is there any chance that
what you're perceiving as a bulge might in fact be corrosion of the
interior of the stem clamp, causing the stem to become locked in
place?
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

Thanks for the reply. You got me thinking about this. I need to correct my
original post as I was doing this a couple of months ago and have forgotten
the exact details. I was successful in removing the original stem, but in
order to put the different sized stem on, I needed to remove a spacer. I
was unsuccessful in removing the top spacer, because the bulge happened to
be just above it. So, to answer your question, the bulge is above the last
spacer and pretty much at the same level of the stem clamp.

John

"Werehatrack" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

On Thu, 15 Sep 2005 04:16:45 GMT, "JS" <[email hidden]>

Quoted message said:

... Someone tell me I'm not being unreasonable as to the danger of riding
on a fork that appears to be compromised.

Without seeing it, making the call is difficult...but I'll throw this
into the discussion for starters, assuming there is a discussion...

If the bulge is at or above the top of the stem's clamp, I do not
personally think it is likely to cause a catastrophic failure, as the
clamp is grabbing the tube at a point where it is presumably still
sound. However, without knowing the mode by which the failure might
propagate, this is an opinion unsupported by any facts.

If the bulge is within the clamp of the stem, and if the steerer is
sound below the bulge, then my guess is that the chances are good that
the steerer will remain together as long as the stresses on it are
light. The gotcha, in my estimation, involves what happens in a hard
bump when leaning forward, or in a hard stop situation, where the
weight transfer forward and/or the impluse loading of the stem goes
up. I have to wonder about the possibility that the tube may deform
and allow the stem to come loose.

Second observation: ISTR that there have been reports of corrosion at
the interface between metal and cabon fiber; is there any chance that
what you're perceiving as a bulge might in fact be corrosion of the
interior of the stem clamp, causing the stem to become locked in
place?
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.