What constitutes “damage” to a carbon seat post
markiegrim
Posts: 136
in Workshop
Recently got a carbon seat post for first time (titanium frame).
Was advised to tighten clamp to around 6-7 Nm. Not sure if 7 was too tight or I went some way past this due to torque wrench being faulty (maybe), but there was a scary squeaking.
So I backed off the pressure and took post out to have a look
Didn’t see any cracking or compression , but there are two (seemingly) surface scratches each about 1.5 inches longitudinally up the post where it was tightened against the metal seat tube
Should I be worried? Is the post likely to fail? LBS reckons should be ok, even if “officially” “damaged”
Thanks for thoughts
Was advised to tighten clamp to around 6-7 Nm. Not sure if 7 was too tight or I went some way past this due to torque wrench being faulty (maybe), but there was a scary squeaking.
So I backed off the pressure and took post out to have a look
Didn’t see any cracking or compression , but there are two (seemingly) surface scratches each about 1.5 inches longitudinally up the post where it was tightened against the metal seat tube
Should I be worried? Is the post likely to fail? LBS reckons should be ok, even if “officially” “damaged”
Thanks for thoughts
0
Comments
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Who advised at 6-7 Nm? Just for reference the numbers on carbon parts are the max and not the recommended. What torque does the manufacture have on the part? I set mine to 4Nm, No idea if it is ok to use but if the sound as the post getting compressed then I would replace and but it down to a lesson learned.0
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Thanks both. Yes I used carbon paste. No torque specified on post or clamp. I’m no going to name supplier, but they even said 9 or 10 Nm wouldn’t do harm. I’ve now set to 50
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Torque figures quoted are usually ones that are enough to hold the post in place an below the tolerance where it would cause damage, I have a post on mine which has what appears to be a nasty crack, in fact its a long scratch.
Carbon paste reduces the amount of torque required to keep the post in place so usually 4-5nm is ample. For example the Deda post I have gives 6nm as a max the torque key I used is set to 5nm an holds it perfectly well. 9-10 would usually be an alloy post.0 -
I think you're fine. My carbon posts haven't let me down. I did have 2 alloy lightweight ones that the saddle mount plug came out of though - guess the saddle was too far back on the clamp and it levered out after a bump.0
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As has been discussed elsewhere, these torque measurements are somewhat meaningless as a greased bolt at 5nm will be applying much more force than a dry bolt at 5nm torque.
It's probably fine but keep an eye on it.0