Cracked seatpost

Steve Gravrock said:

The other day I noticed some damage to my carbon fiber seatpost. There
was a vertical crack running along one side of the notch in the seat
tube. The post was indented on one side of the crack, and scored along
the top of the seat tube on the same side. It looked like the damage was
due to overtightening, however, the binder bolt wasn't particularly
tight. Certainly it was not as tight as I'd usually have it with an
aluminum seatpost.

Is that sort of damage common or easy to cause, in the experience of
those in this group? The bike shop owner thought it was unusual enough
to send the post back to the manufacturer even though it was out of
warranty. I got a free replacement, which I'm quite happy about, but the
incident makes me a little nervous about carbon fiber parts in general.

I was getting some slippage on carbon posts and was worried about
cracking one from overtightening, or even damaging the seat tube, so
got the Tacx special goop to keep the post from slipping. FSA sells
some too but they're perpetually out of stock on it. It feels like a
very fine grit in a greaselike substance. It's expensive as hell but
seems like it will last for many many years, and I swap out posts a
lot. I put just a dab on the post before installing it (carbon post
in carbon seattube, or even a carbon post in a steel on alum frame, or
alum post in a carbon tube), and I can put my mind at ease by leaving
it torqued slightly loose, and haven't had any slippage yet. I also
use it for carbon bars on any material stem, otherwise bars routinely
slip on the big chuckholes on descents, or routinely on the cross
bike, and I certainly don't want to crank down on nice carbon bars. I
just ordered the ordered the Pedros torque wrench and bit set to
really set my mind at ease in that department.

Bill Westphal

Bill Westphal said:

I was getting some slippage on carbon posts and was worried about
cracking one from overtightening, or even damaging the seat tube, so
got the Tacx special goop to keep the post from slipping. FSA sells
some too but they're perpetually out of stock on it. It feels like a
very fine grit in a greaselike substance.

So finely ground coffee, semolina, rice etc (i.e. something a bit coarser
than flour) in vaseline might work at a pinch? :-)

On Jul 13, 12:38 am, Steve Gravrock <[email hidden]>

Quoted message said:

The other day I noticed some damage to my carbon fiber seatpost. There
was a vertical crack running along one side of the notch in the seat
tube. The post was indented on one side of the crack, and scored along
the top of the seat tube on the same side. It looked like the damage was
due to overtightening, however, the binder bolt wasn't particularly
tight. Certainly it was not as tight as I'd usually have it with an
aluminum seatpost.

Is that sort of damage common or easy to cause, in the experience of
those in this group? The bike shop owner thought it was unusual enough
to send the post back to the manufacturer even though it was out of
warranty. I got a free replacement, which I'm quite happy about, but the
incident makes me a little nervous about carbon fiber parts in general.

No uncommon and why we turn the clamp around to face 180 degrees out
from the seat tube 'notch'. When tightening, the 'hole'
for the seatpost gets oval, which can cause what you saw. Rotating
the clamp helps to keep the hole more round.

Michael Warner said:

Bill Westphal said:

I was getting some slippage on carbon posts and was worried about
cracking one from overtightening, or even damaging the seat tube, so
got the Tacx special goop to keep the post from slipping. FSA sells
some too but they're perpetually out of stock on it. It feels like a
very fine grit in a greaselike substance.

So finely ground coffee, semolina, rice etc (i.e. something a bit coarser
than flour) in vaseline might work at a pinch? :-)

interestingly, that's what cannondale have on all their new bikes - it's
a grease with a polymer "abrasive" in it. a bit like the abrasive used
in workshop hand cleaners. i'm not sure about the vaseline though. if
i were going to try rolling my own, i'd use a silicone grease to avoid
reaction with the post materials.

Qui si parla Campagnolo said:

On Jul 13, 12:38 am, Steve Gravrock <[email hidden]>

Quoted message said:

The other day I noticed some damage to my carbon fiber seatpost. There
was a vertical crack running along one side of the notch in the seat
tube. The post was indented on one side of the crack, and scored along
the top of the seat tube on the same side. It looked like the damage was
due to overtightening, however, the binder bolt wasn't particularly
tight. Certainly it was not as tight as I'd usually have it with an
aluminum seatpost.

Is that sort of damage common or easy to cause, in the experience of
those in this group? The bike shop owner thought it was unusual enough
to send the post back to the manufacturer even though it was out of
warranty. I got a free replacement, which I'm quite happy about, but the
incident makes me a little nervous about carbon fiber parts in general.

No uncommon and why we turn the clamp around to face 180 degrees out
from the seat tube 'notch'. When tightening, the 'hole'
for the seatpost gets oval, which can cause what you saw. Rotating
the clamp helps to keep the hole more round.

hot-dog, we have a wiener!

correct sir - the best solution.

Quoted message said:

No uncommon and why we turn the clamp around to face 180 degrees out
from the seat tube 'notch'. When tightening, the 'hole'
for the seatpost gets oval, which can cause what you saw. Rotating
the clamp helps to keep the hole more round.

---------
Just did the same, on one of my bikes due the problem described.

Steve Gravrock said:

The other day I noticed some damage to my carbon fiber seatpost. There
was a vertical crack running along one side of the notch in the seat
tube. The post was indented on one side of the crack, and scored along
the top of the seat tube on the same side. It looked like the damage was
due to overtightening, however, the binder bolt wasn't particularly
tight. Certainly it was not as tight as I'd usually have it with an
aluminum seatpost.

Is that sort of damage common or easy to cause, in the experience of
those in this group? The bike shop owner thought it was unusual enough
to send the post back to the manufacturer even though it was out of
warranty. I got a free replacement, which I'm quite happy about, but the
incident makes me a little nervous about carbon fiber parts in general.

Not in general, but carbon and seatpost are a dumb combination IMHO.

Lou
--
Posted by news://news.nb.nu (http://www.nb.nu)

Michael Warner said:

Bill Westphal said:

I was getting some slippage on carbon posts and was worried about
cracking one from overtightening, or even damaging the seat tube, so
got the Tacx special goop to keep the post from slipping. FSA sells
some too but they're perpetually out of stock on it. It feels like a
very fine grit in a greaselike substance.

So finely ground coffee, semolina, rice etc (i.e. something a bit coarser
than flour) in vaseline might work at a pinch? :-)

Maybe one could re-cycle bearing grease.

On Fri, 13 Jul 2007 11:36:02 -0600, Bill Westphal <[email hidden]>

Quoted message said:

Michael Warner said:

Bill Westphal said:

I was getting some slippage on carbon posts and was worried about
cracking one from overtightening, or even damaging the seat tube, so
got the Tacx special goop to keep the post from slipping. FSA sells
some too but they're perpetually out of stock on it. It feels like a
very fine grit in a greaselike substance.

So finely ground coffee, semolina, rice etc (i.e. something a bit coarser
than flour) in vaseline might work at a pinch? :-)

Maybe one could re-cycle bearing grease.

That is funny. If it was a joke. If it wasn't a joke, it's clever.

--
JT
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Visit http://www.jt10000.com
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jim beam said:

interestingly, that's what cannondale have on all their new bikes - it's
a grease with a polymer "abrasive" in it. a bit like the abrasive used
in workshop hand cleaners.

I imagine the particles shouldn't be too hard or pointy, though, which is
why I thought of food rather than minerals.

Lou Holtman said:

Steve Gravrock said:

The other day I noticed some damage to my carbon fiber seatpost. There
was a vertical crack running along one side of the notch in the seat
tube. The post was indented on one side of the crack, and scored along
the top of the seat tube on the same side. It looked like the damage was
due to overtightening, however, the binder bolt wasn't particularly
tight. Certainly it was not as tight as I'd usually have it with an
aluminum seatpost.

Is that sort of damage common or easy to cause, in the experience of
those in this group? The bike shop owner thought it was unusual enough
to send the post back to the manufacturer even though it was out of
warranty. I got a free replacement, which I'm quite happy about, but the
incident makes me a little nervous about carbon fiber parts in general.

Not in general, but carbon and seatpost are a dumb combination IMHO.

Lou

imo, it's a /great/ combination. vibration attenuation just where you
need it. all with lightness and superior fatigue strength. nothing not
to love.

Michael Warner said:

jim beam said:

interestingly, that's what cannondale have on all their new bikes - it's
a grease with a polymer "abrasive" in it. a bit like the abrasive used
in workshop hand cleaners.

I imagine the particles shouldn't be too hard or pointy, though, which is
why I thought of food rather than minerals.

no, the cannondale "abrasive" is a soft-ish material like low density
polythene. imagine granulated 6-pack holder

jim beam said:

Quoted message said:

I imagine the particles shouldn't be too hard or pointy, though, which is
why I thought of food rather than minerals.

no, the cannondale "abrasive" is a soft-ish material like low density
polythene. imagine granulated 6-pack holder

I'd rather think about food :-)

jim beam said:

Lou Holtman said:

Steve Gravrock said:

The other day I noticed some damage to my carbon fiber seatpost. There
was a vertical crack running along one side of the notch in the seat
tube. The post was indented on one side of the crack, and scored along
the top of the seat tube on the same side. It looked like the damage was
due to overtightening, however, the binder bolt wasn't particularly
tight. Certainly it was not as tight as I'd usually have it with an
aluminum seatpost.

Is that sort of damage common or easy to cause, in the experience of
those in this group? The bike shop owner thought it was unusual enough
to send the post back to the manufacturer even though it was out of
warranty. I got a free replacement, which I'm quite happy about, but the
incident makes me a little nervous about carbon fiber parts in general.

Not in general, but carbon and seatpost are a dumb combination IMHO.

Lou

imo, it's a /great/ combination. vibration attenuation just where you
need it. all with lightness and superior fatigue strength. nothing not
to love.

Lightness? Many CF seatpost are heavier or marginal lighter then good
quality Al ones.
Vibration attenuation? I don't believe that.
Superior fatigue strength? Maybe, but only if:
- not damaged by overtightening the seatpost bolt,
- not scratched because of clamping it in the workstand or bikerack,
- not scratched by the saddlebag,
- proper fit in the seattube (slipping, creaking). Aluminum post can be
machined within closer tolerances in diameter or roundness.

Nothing not to love or to many things to worry about?

Cheers,

Lou
--
Posted by news://news.nb.nu (http://www.nb.nu)

Lou Holtman said:

jim beam said:

Lou Holtman said:

Steve Gravrock wrote:
> The other day I noticed some damage to my carbon fiber seatpost. There
> was a vertical crack running along one side of the notch in the seat
> tube. The post was indented on one side of the crack, and scored along
> the top of the seat tube on the same side. It looked like the damage
> was
> due to overtightening, however, the binder bolt wasn't particularly
> tight. Certainly it was not as tight as I'd usually have it with an
> aluminum seatpost.
>
> Is that sort of damage common or easy to cause, in the experience of
> those in this group? The bike shop owner thought it was unusual enough
> to send the post back to the manufacturer even though it was out of
> warranty. I got a free replacement, which I'm quite happy about, but
> the
> incident makes me a little nervous about carbon fiber parts in general.

Not in general, but carbon and seatpost are a dumb combination IMHO.

Lou

imo, it's a /great/ combination. vibration attenuation just where you
need it. all with lightness and superior fatigue strength. nothing
not to love.

Lightness? Many CF seatpost are heavier or marginal lighter then good
quality Al ones.

some are, but they're rarely the same length and that doesn't make
accurate comparison. generally, like for like, carbon is lighter. as
you would expect from a material that has a much higher strength/weight
ratio than aluminum.

Quoted message said:

Vibration attenuation? I don't believe that.

this is not faith, this is science. carbon attenuates vibration.

Quoted message said:

Superior fatigue strength? Maybe, but only if:
- not damaged by overtightening the seatpost bolt,

#1 position for seat post fatigue is the point where it's clamped into
the frame. carbon is much better in fatigue in that position.
otherwise, most carbon posts use the same aluminum clamp as their
aluminum brethren, so no advantage there.

Quoted message said:

- not scratched because of clamping it in the workstand or bikerack,

carbon is superior - /much/ less sensitive to fatigue in this respect.

Quoted message said:

- not scratched by the saddlebag,

see above.

Quoted message said:

- proper fit in the seattube (slipping, creaking). Aluminum post can be
machined within closer tolerances in diameter or roundness.

rubbish. carbon is molded then machined. then it's clear-coated.
there may be minor anomalies in the latter, but they really are trivial.

Quoted message said:

Nothing not to love or to many things to worry about?

if you understand the science, carbon /is/ the better choice.

Qui si parla Campagnolo said:

No uncommon and why we turn the clamp around to face 180 degrees out
from the seat tube 'notch'. When tightening, the 'hole'
for the seatpost gets oval, which can cause what you saw. Rotating
the clamp helps to keep the hole more round.

Do you do that for all seatposts, or just carbon fiber?

In article <[email hidden]>,

Steve Gravrock said:

Qui si parla Campagnolo said:

No uncommon and why we turn the clamp around to face 180 degrees out
from the seat tube 'notch'. When tightening, the 'hole'
for the seatpost gets oval, which can cause what you saw. Rotating
the clamp helps to keep the hole more round.

Do you do that for all seatposts, or just carbon fiber?

I thought up this scheme on my own and use it on a
steel frame with Al seatpost.

At the seatpost cut in the seat tube the clamp is
round, and therefore the clamp does not abet the seat
tube edges at the cut in their tendency to fold
inwards.

Likewise at the clamp jaws the seat tube is round, and
therefore the seat tube does not abet the clamp jaws in
their tendency to fold inwards.

--
Michael Press

On Jul 14, 11:24 am, Steve Gravrock <[email hidden]>

Quoted message said:

Qui si parla Campagnolo said:

No uncommon and why we turn the clamp around to face 180 degrees out
from the seat tube 'notch'. When tightening, the 'hole'
for the seatpost gets oval, which can cause what you saw. Rotating
the clamp helps to keep the hole more round.

Do you do that for all seatposts, or just carbon fiber?

Just carbon fiber altho I have seen a thin walled aluminum post get
dented in at the rear. Probably wouldn't hurt for any post, since they
are trying to be so light these days.

I noticed a notch, but no crack, in my carbon fiber seat post. Is it too
late to swivel the clamp 180 degrees?

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

Quoted message said:

On Jul 13, 12:38 am, Steve Gravrock <[email hidden]>

Quoted message said:

The other day I noticed some damage to my carbon fiber seatpost. There
was a vertical crack running along one side of the notch in the seat
tube. The post was indented on one side of the crack, and scored along
the top of the seat tube on the same side. It looked like the damage was
due to overtightening, however, the binder bolt wasn't particularly
tight. Certainly it was not as tight as I'd usually have it with an
aluminum seatpost.

Is that sort of damage common or easy to cause, in the experience of
those in this group? The bike shop owner thought it was unusual enough
to send the post back to the manufacturer even though it was out of
warranty. I got a free replacement, which I'm quite happy about, but the
incident makes me a little nervous about carbon fiber parts in general.

No uncommon and why we turn the clamp around to face 180 degrees out
from the seat tube 'notch'. When tightening, the 'hole'
for the seatpost gets oval, which can cause what you saw. Rotating
the clamp helps to keep the hole more round.