Question on developing split in carbon steerer tube

Kovie said:

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

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"

On 25 Jun 2004 12:41:06 GMT, [email hidden] (Qui si parla

Campagnolo ) said:

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 [censored] 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.

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 hidden]

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

Quoted message said:

On 25 Jun 2004 12:41:06 GMT, [email hidden] (Qui si parla

Campagnolo ) said:

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

Quoted message said:

Quoted message said:

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 [censored] 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.

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 hidden]

"Qui si parla Campagnolo " <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

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"

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.

--

Kovie said:

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

Quoted message said:

Quoted message said:

Kovie-<< Is this common, and what could have caused

this? Am I correct in

Quoted message said:

Quoted message said:

assuming
that it's unwise to ride this fork, and that it needs to be replaced right
away? >><BR><BR>

Quoted message said:

On 25 Jun 2004 12:41:06 GMT, [email hidden] (Qui si parla

Campagnolo ) said:

Not common, don't ride it.

Quoted message said:

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

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"

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 hidden]