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Discussion Starter · #1 ·
Hello, new here but not new to riding. I mostly ride a '13 Stumpjumper FSR 29er but recently acquired an '11 Stumpjumper S-works HT for those nice long winding singletracks. Purchased it from a bike store and had it looked over. Been riding it for a little while and it rides great. The only issue is the seatpost likes to slide down as I ride. I realize you have to be careful when tightening carbon and use torque wrench but on the trail, its hard to measure. Im not sure if I have ever over tightened it but heard some talk about carbon seatposts snapping which has gotten me worried. I noticed these marks on my seatpost before and just brushed them aside as scratches since they are really on the white part but you never can be too careful. Are they just scratches or worse? Also, any tips to keep the seatpost from sliding down? I really had any trouble with alloy ones before. Thanks.
And theres also a pic of possibly my new favorite bike :)
 

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SS Pusher Man
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Carbon post in a carbon frame.......use some friction paste to help with the post slipping.

Looks like scratches.

Does it creak when you are seated? IF they were cracks, and that big, it would be making a hell of a lot of noise.
 

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Discussion Starter · #3 ·
No creaking sound. I did over-tighten it accidently once which made a cracking sound but after giving the seatpost the once over, the only marks are these scratches. They all look like scratches to me unless theres a crack hidden in there somewhere
 

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I like pie.
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Looks like scratches.

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Scratches don't cast shadows. Note picture #1.

The OP has a crack in his seatpost and a rather nasty one.

If the OP has any interest in children of his own (or normal bowel functions) a $150investment in a new carbon seat post is a very good idea.
 

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I agree. That post is toast. It would seem you need a new post and a torque wrench while you're at it.
 

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Discussion Starter · #6 ·
Could you point the crack? I may be mistaken but the line I think you are referring too that is casting a shadow is the one at the top that comes down at an angle. That one seems to be part of the post design and wraps around in picture 2. I can take better pictures if need be.
I have been aware of using a torque wrench but on the trail, you don't always have access to everything you need and need to improvise. I have heard the torque wrench can be off though. I just hope I don't have to get a new post and a $200 or so torque wrench
 

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I'm no expert but the top two pics with the angular line going across the post look like something on the post itself, like clear tape or a clear coast finish.

The wavy lines below are just scratches from twisty, turning it down into or up out of the frame.

If it's not making a creaking sound, it's probably not destabilized.
 

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They don't stay cracked for long either. They usually just break, that's my own experience.


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With friction paste i tighten the clamp so it really doesn't take much pressure to close, err on the side of caution and worst case is it slips a little. I learned my lesson about not using the paste with a cracked a carbon bar.
 

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Discussion Starter · #11 ·
Did the quarter test. Everything sounds the same.
It seems that about half of you think it is a scratch and the other half are saying it is a crack. The marks are only on the lower white area. The upper part of the line casting a shadow is glossy while the lower part has a dull finish and that is where the marks are.
I will be investing in friction paste for sure next time.
I know to use a torque wrench and tighten it to the post specs but do any of you carry a torque wrench while on the trail?
 

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Once I ham fisted a qr clamp with a carbon post. Heard the crunching sound. A couple of months later I noticed the ht felt a little more plush than normal. Sure enought the post was broken half way around at the clamp. Stood the last couple of miles to finish the ride. Replaced with a Thomson.

If you heard a crushing sound. The post is compromised. Just a matter of time before it fails.
 

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Discussion Starter · #14 ·
looks like it's been out in the sun a little while
Could be just that. The rest of the bike is in great condition though. The paint might have just cracked in the sun. I don't think that part of the seatpost has any clear coat protection. I don't really want to have to change seatposts. I quite like the one on it but I have heard hear great things about Thomson's.
 

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Pics 1 and 2 do appear to be related to the finish, as it is perfectly straight and symmetrical on the left/right side of the bike. Also below the line it is a matte finish, above appears more gloss. If you are unsure have your LBS inspect it for a more professional first hand opinion instead of putting your manhood in jeopardy based on guesstimating via Internet pics. :)
 

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Could be just that. The rest of the bike is in great condition though. The paint might have just cracked in the sun. I don't think that part of the seatpost has any clear coat protection. I don't really want to have to change seatposts. I quite like the one on it but I have heard hear great things about Thomson's.
i run a Thomson seat post on my jamis dragon 29er and its worked just fine, going with Thomson isn't a bad idea
 

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Discussion Starter · #18 ·
Pics 1 and 2 do appear to be related to the finish, as it is perfectly straight and symmetrical on the left/right side of the bike. Also below the line it is a matte finish, above appears more gloss. If you are unsure have your LBS inspect it for a more professional first hand opinion instead of putting your manhood in jeopardy based on guesstimating via Internet pics. :)
I tried a couple LBS and they have conflicting opinions. One says its just scratches and not to worry and another LBS thinks worse, and then they tried to sell me a new seatpost. I was just hoping there were some carbon gurus here who might have extra insight into it. I havent had much experience with carbon as I only ran alloy before and steel even before that. I do appreciate all the advice I have been getting. I definitely will be looking at new seatposts.
 

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Just took another look at the pics again. That a decent amount of saddle offset. Not to mention a rather long looking stem. Is this even the correct size frame for you? A seatpost with aggressive setback is generally a band aid for a frame that is to small.

At any rate. If you get a new post, keep set back in mind. Doesn't look like a 0 offset post is going to work for you. Good luck.
 

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Discussion Starter · #20 ·
Just took another look at the pics again. That a decent amount of saddle offset. Not to mention a rather long looking stem. Is this even the correct size frame for you? A seatpost with aggressive setback is generally a band aid for a frame that is to small.

At any rate. If you get a new post, keep set back in mind. Doesn't look like a 0 offset post is going to work for you. Good luck.
I recently bought it and so that picture is how it was setup for the previous owner. The previous owner was taller than me and so that will explain the setup. I could go for less setback post and shorter stem with no problem
 
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