Bicycle Mechanics - Is this seatpost safe to use?
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I recently bought a carbon seatpost online that appears to be damaged inside the shaft. Do these look like cracks to you guys?
Surely that can't be normal? I've seen inside a different carbon seatpost before and it didn't look anything like that.
I also noticed that the 2 load bearing thicker sections of the inner wall are not perfectly aligned with the front and rear of the post, the thickness is a little bit to the sides of the post instead. This has me concerned that it won't have proper weight distribution and could cause extra flex and stress when sitting on it. Am I correct about that?
Any opinions on this would be much appreciated.
09-28-12, 06:45 AM
Without having it in my hands it is hard to know. From what I can see in the pictures it looks like casting marks to me but I would never use carbon when in doubt. Carbon gives no warning when it is going to fail. Roger
Looks like casting marks to me, too.
Any cracks showing on the outside?
09-28-12, 09:32 AM
For a carbon post I'd say those are cracks also looks like someone cut it it may have cracked if the clamped it in a vice to hold it.
This pattern is classic for a post that was ovalized when clamped improperly. This could have been done outside the bike in a vise, co could have happened when clamped into an oval or mis-sized seat tube.
Stress cracking like this is a precurser to failure, especially if the cracks extend near to the top of the seat tube. OTOH if the cracks only extend a short ways, and you'll have at least 2.5" of unaffected post in the frame you may be able to use this post safely. But I'd be attentive to any hint (creaking or sense of flexing) that the crack is moving up near the clamped area. If that happens the post is toast.
I wonder if you can still sleeve that thing with a thin gauge inner Aluminum tube and epoxy? A long shot, but it might be worth trying anyway....if it will be hard to find a replacement.
09-28-12, 12:31 PM
More direct , just buy a new aluminum metal seatpost..
No cracks showing on the outside or deeper inside the post that I can see. I suppose they could be casting marks as some of them protrude outwards from the inner wall, I guess cracks probably wouldn't be like that. Maybe they just weren't sanded down like the rest of the inside seems to have been. I have to cut the post down about 130-150mm anyway so if they are cracks hopefully that will get rid of any potential issues.
I do own a nice Thompson Elite aluminum post but its kind of heavy which is one of the main reasons I wanted to try out a carbon post.
09-29-12, 02:17 AM
that is the bottom of the post right? and its only for the first inch or 2?? So long as it is inserted deep enough below the minimum insertion point you should be ok??
10-03-12, 09:55 PM
I know absolutely nothing about carbon, as the only carbon I have had is carbon forks and Carbon in my Firearms. But I would hate for that seat to fail and have a sharp piece of carbon stab me in my important/special parts!!!
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