Question on developing split in carbon steerer tube



K

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]
 
A

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
 
Q

Qui Si Parla Ca

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>

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"
 
C

carlfogel

Guest
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 ******* 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.
 
K

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]

<[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 ******* 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.
 
K

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]

"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"
 

Weisse Luft

New Member
May 28, 2004
1,306
0
0
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.
 
C

carlfogel

Guest
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
 
A

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
 
K

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]