carbon seat post question

[quansoo]

I changed my pedal system, and as a result have been tweaking my saddle height. I have a PMP carbon post on my HSG IT, which I bought last season. I know that I should use a torque wrench to tighten it properly but have been figuring that I'd just tighten until it sort of felt right.

Today I was riding, stopped, made a slight adjustment, tightened it up once, fiddled with some other stuff, and then thought I'd just give it another gentle touch more. I heard a a slight tick, and immediately backed it off slightly. It wasn't a loud sound, or a crunching sound, but now I'm a bit concerned. Though I looked it over carefully, and it looks fine to me, a busted post could have unpleasant consequences.

I guess I could pull the post off the frame and really look closely at it - perhaps that's the place to start. But I figured I'd ask the knowledgable folks here if there is any real cause for concern.

Thanks in advance. Any help greatly appreciated.

[1centaur]

The "slight tick" could have been the metal in the clamp.

Pull it off, look at it very carefully, if it's fine put it back in using carbon paste on the post and grease on the clamp screw so you have to torque it less to get the same effect.

[bkboom123]

+1


I have had that happen a few times on a couple different bikes.....Never had a problem though. I just looked the post over and found nothing wrong. It has been over a year since and still no problems.

[quansoo]

Many thanks. I sort of feel better already.

[mike p]

Very few people including pro's torque a seatpost.

Mike

[LO^OK]

Not to rain on your parade but just a visual inspection might not reveal any structural damage/ micro fractures as in most cases the top carbon layer is purely cosmetic.

To complicate the matter, different posts, apparently depending on the technology used, have specified different torque values. For example I have Look Ergopost 2 - a design several years old - with recommended torque of 2 Nm; on the other hand, recently saw the latest Time post clamp rated at 4 Nm. These are pretty low values and easy to exceed when casually tightening the bolts. No need to tell, I've got a torque wrench before I bought a carbon post.

[sspielman]

First, always use a torque wrench to get enough-but not too much tightness....Second, lightweight parts-especially carbon ones- are meant to be installed once and left alone. I don't know any other way to say this, but if you are fiddling with your seatpost height, you are not ready for the carbon post...use a Kalloy throwaway for that and when you have it sorted out, switch to the carbon one.....

[Dave]

So much misinformation. Torques in the 2-4Nm would be unlikely to hold any seatpost in place and should not be related to the brand of post being used.

The idea that a well made post can't be removed and reinstalled many times is just not correct.

I've been using carbon posts since 2000 and never once used a torque wrench to tighten the clamp bolt on any of 7 different frames (2 Colnagos, 1 Fondriest, 4 LOOKs) and never had any problems.

After reading about some carbon steerers cracking, I did my own test with a husky stem having two M6 clamp bolts, I installed it on a scrap piece of cutoff steering tube and used a long handled hex wrench to tighten it to a ridiculously high torque, with no compression plug in place for support. The severe overtightening caused no problem at all. I was more afraid of stripping the threads in the stem.

If you do manage to crack a steerer or seatpost, it's most likely do to a poor (loose) fit. If the frame has a split in the top of the seat tube, turn the clamp around so the split in the clamp does not line up with the split in the seat tube. LOOKs have two splits in the seat tube. I've never bothered to turn the clamp to avoid alignment with the slots.

To minimize the required torque, use some Tacx assembly paste or similar product. FSA posts now come with a small amount of assembly paste.

[Bob Ross]

I don't know any other way to say this, but if you are fiddling with your seatpost height, you are not ready for the carbon post.

Right, 'cuz everyone knows that professional cyclists never tweak their fit...


:butt:

[kgreene10]

For what it's worth, I routinely hear a tick sound when tightening my Serotta seat clamp on a Thomson alu post. In my case, I'm pretty certain it's the sound the bolt makes in the collar when it gets tight.

[sspielman]

I tend to err on the side of caution....but then again, I never break anything....

[MIN]

as a tangent - i just bought a new seatpost collar and it came with a light coating of locktite on the threads of the bolt. i noticed that it took noticeably more torque on the bolt (subjective) to hold the post in place.

would it be better to grease the seatpost collar instead?

[quansoo]

I felt no need to adjust the height until I switched pedal systems. Though I didn't think to mention it in my original post, at the same time that I switched pedals, I also changed my saddle.

I think I'll err on the side of caution, have a good look at the thing, get the height dialed in and torque the post to the manufacturer's spec.

Thanks again for the help.

[LO^OK]

So much misinformation. Torques in the 2-4Nm would be unlikely to hold any seatpost in place and should not be related to the brand of post being used.

The idea that a well made post can't be removed and reinstalled many times is just not correct.

I've been using carbon posts since 2000 and never once used a torque wrench to tighten the clamp bolt on any of 7 different frames (2 Colnagos, 1 Fondriest, 4 LOOKs) and never had any problems.

After reading about some carbon steerers cracking, I did my own test with a husky stem having two M6 clamp bolts, I installed it on a scrap piece of cutoff steering tube and used a long handled hex wrench to tighten it to a ridiculously high torque, with no compression plug in place for support. The severe overtightening caused no problem at all. I was more afraid of stripping the threads in the stem.

If you do manage to crack a steerer or seatpost, it's most likely do to a poor (loose) fit. If the frame has a split in the top of the seat tube, turn the clamp around so the split in the clamp does not line up with the split in the seat tube. LOOKs have two splits in the seat tube. I've never bothered to turn the clamp to avoid alignment with the slots.

To minimize the required torque, use some Tacx assembly paste or similar product. FSA posts now come with a small amount of assembly paste.

Labelling my words as "misinformation" when I just pass on manufacturer's recommendations is not just rude but constitute a true misinformation. And I can assure you that Look specified 2 Nm torque is pretty sufficient with the post held tightly in place.

If giving advice on a public forum better be to read and observe the instructions that come with high end components than to promote Luddite's subjective, and non transferrable, feel/skill.

[Dave]

Labelling my words as "misinformation" when I just pass on manufacturer's recommendations is not just rude but constitute a true misinformation. And I can assure you that Look specified 2 Nm torque is pretty sufficient with the post held tightly in place.

If giving advice on a public forum better be to read and observe the instructions that come with high end components than to promote Luddite's subjective, and non transferrable, feel/skill.


As a mechanical engineer, I'll stand by my statement. It's not intened to be rude, just realistic. I've never seen any torque spec under 5Nm (for a stem not a seatpost). 2Nm is ridiculously low. I know I've tightened the seatpost clamp on LOOK frames far more than that and had a post slip. It's not rude to disagree. I would feel negligent recommending a torque value that low to anyone.

If a torque of only 2-4Nm was adequate, I would not expect a husky M6 bolt for this application. A smaller and lighter M5 would be more than adequate for at least 7Nm.

[nicrump]

you guys with ticking clamps need to grease not just the threads but also under the bolt head and both sides of the washer. same on your stem bolts and the bolts on the cradle.