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Carbon seatpost strength

Old 12-12-05, 05:36 PM
  #1  
trekkie820
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Carbon seatpost strength

The bike I want has a carbon seatpost, but I am a cool 240. Is there a chance that this thing will snap on me under any conditions?
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Old 12-12-05, 06:00 PM
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Yes, there is a chance it will snap. I was 125 lbs when I had mine ... and it snapped. Apparently my little un-muscular arms were strong enough to tighten the clamp down too much. IMO if a 125 lb girl who isn't known for her upper body strength can snap a carbon seatpost ...... carbon seatposts aren't worth it!!

I've now got a much sturdier aluminum seatpost.
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Old 12-12-05, 06:02 PM
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e mail the manufacturer and ask if the seat post has a weight limit.
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Old 12-12-05, 08:56 PM
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Core sample waiting to happen. Don't do it.
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Old 12-12-05, 11:00 PM
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I have carbon seatpost on two bikes 210lbs. No problems yet.
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Old 12-12-05, 11:33 PM
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Originally Posted by curt in denver
I have carbon seatpost on two bikes 210lbs. No problems yet.
Yet. Even you said it.
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Old 12-12-05, 11:46 PM
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Anyone else break one?
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Old 12-13-05, 02:45 AM
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Originally Posted by curt in denver
Anyone else break one?
Ask Climbo, in The Aussie Thread. It was either him or GW.
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Old 12-13-05, 09:27 AM
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Maybe I can get the shop to swap it out before I buy. That is the last thing that i need, a sharp half carbon seatpost up my ass.
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Old 12-13-05, 10:02 AM
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I weighed 240 when i started riding my carbon seatpost...I'm down to 200 now, though.
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Old 12-13-05, 10:17 AM
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I have broken two on different road bikes in the past two months. My weight fluctuated between 185-195 during this time. I have never tried carbon posts on my MTB's.

These are the posts I have destroyed

1. Sworks carbon with the PAVE insert cracked at the rear seat clamp.

2. OEM that came on a 2004 allez comp. cracked at seat clamp.


never again. can you say thomson?
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Old 12-13-05, 10:19 AM
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I can trust a carbon fork, but something like the seatpost I need it to be metal. My Bonty Sport seatpost (aluminum) on my MTB has taken a pounding, and it has no cracks anywhere.
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Old 12-13-05, 11:25 AM
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Originally Posted by trekkie820
I can trust a carbon fork,
I wouldn't do that either. I changed out my carbon forks for steel because I didn't trust them ... AND I've seen carbon forks which have snapped too.
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Old 12-13-05, 11:35 AM
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Originally Posted by Expatriate
Core sample waiting to happen. Don't do it.
Very funny. Vivid picture comes to mind.
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Old 12-13-05, 01:20 PM
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I trust a carbon fork because of what I have seen them do as rigid MTB forks in rock gardens, with rather robust riders.
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Old 12-13-05, 01:54 PM
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One of the guys in The Aussie Thread was just talking abut a mate of his that had his CF fork fail. That had to hurt. Call me grouchy, but the only CF on my bike is the headset spacers. At least with titanium, the expense can be justified by nearly zero risk.
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Old 12-13-05, 02:34 PM
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Originally Posted by trekkie820
I trust a carbon fork because of what I have seen them do as rigid MTB forks in rock gardens, with rather robust riders.

The snapped forks I saw broke under a guy who wasn't very big ... and who was riding downhill on a very smooth road. He was hospitalized.


That's two carbon failures (my seatpost and his forks) I've seen in less than a year ... and enough for me to consider carbon as a non-viable material for a bicycle.
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Old 12-13-05, 06:40 PM
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Originally Posted by Machka
That's two carbon failures (my seatpost and his forks) I've seen in less than a year ... and enough for me to consider carbon as a non-viable material for a bicycle.
So I guess a Carbon Fiber Wheelset is out of the question?
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Old 12-13-05, 06:45 PM
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Originally Posted by TomM
So I guess a Carbon Fiber Wheelset is out of the question?
Oddly, I would probably be more inclined to trust a wheel built with CF than a frame, seatpost, handlebar, stem, or fork. There's no clamping area to get messed up by some heavy-handed wrench jockey, and there's no concentration of stress in one area. But since I'm not a roadie, it will never happen.
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Old 12-13-05, 06:47 PM
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Originally Posted by TomM
So I guess a Carbon Fiber Wheelset is out of the question?

Does such a thing exist?

If so ... I wouldn't even consider it.
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Old 12-13-05, 07:05 PM
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Originally Posted by Machka
Does such a thing exist?

If so ... I wouldn't even consider it.
Plastic wheels...

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Old 12-13-05, 07:47 PM
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Oddly enough, I have yet to break a CF component. However, I have a string of broken Al and steel components in my past.
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Old 12-13-05, 08:22 PM
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Originally Posted by MERTON
that's cuz you're like... carbon man...
I'm not saying that CF can't break. Nothing is indestructable. Many people believe that Ti is yet my Ti spindle pedals have a 185 lbs. weight limit. Choice of material is immaterial. It's all about how the part is designed.
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Old 12-13-05, 08:26 PM
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CF Bento box?
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Old 12-13-05, 08:34 PM
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Originally Posted by Expatriate
CF Bento box?
Well, it's sort of half-there. The fibre is nylon... all I need is some resin.
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