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Clydesdales/Athenas (200+ lb / 91+ kg) Looking to lose that spare tire? Ideal weight 200+? Frustrated being a large cyclist in a sport geared for the ultra-light? Learn about the bikes and parts that can take the abuse of a heavier cyclist, how to keep your body going while losing the weight, and get support from others who've been successful.

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Old 05-26-11, 10:32 AM   #1
big50_1
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Seatpost-that doesn't bend!

I have a 2000 Bianci Avenue hybrid that is bullet proof. BUT the seatpost (alloy) bends slightly over time at the seatpost/seat tube juncture. Just a small bend but I'm concerned that I'll be out THERE and the post will break. Any recommendations on a strong, not easily bent seatpost?
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Old 05-26-11, 11:10 AM   #2
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Thomson Elite
http://www.jensonusa.com/store/produ...px?sc=MR08&x=y

Supposedly as good as it gets in the world of seat posts.
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Old 05-26-11, 11:16 AM   #3
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As above, make sure there is plenty of post in the seat tube.
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Old 05-26-11, 11:16 AM   #4
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Old 05-26-11, 11:53 AM   #5
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Ditto on the Thomson. You get what you pay for...
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Old 05-26-11, 12:00 PM   #6
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I think the Thompson is what I've got now. My old seatpost got corroded and stuck into place. I replaced with a Thompson. The old seatpost was circular inside and circular outside. The Thompson is circular outside and oval inside. In other words, it's stronger front-to-back than it is side-to-side. I mention this because that is a weight-saving issue that you're paying extra for, not a strength-adding feature, so I wouldn't be so sure that it's actually stronger than a cheaper thicker heavier post.

You might also look at how your seat is adjusted front-to-back, which can add some extra stress on the post.
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Old 05-26-11, 12:21 PM   #7
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Just remember the other model Thomson has a weight limit.
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Old 05-26-11, 01:10 PM   #8
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Thanks for the info.
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Old 05-26-11, 01:26 PM   #9
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I think the Thompson is what I've got now. My old seatpost got corroded and stuck into place. I replaced with a Thompson. The old seatpost was circular inside and circular outside. The Thompson is circular outside and oval inside. In other words, it's stronger front-to-back than it is side-to-side. I mention this because that is a weight-saving issue that you're paying extra for, not a strength-adding feature, so I wouldn't be so sure that it's actually stronger than a cheaper thicker heavier post.

You might also look at how your seat is adjusted front-to-back, which can add some extra stress on the post.
From the "cup half full" perspective, the Thomson allows for greater strength without too much of a weight penalty. Most decent posts will be thusly designed. Cheaper posts, while maybe physically stronger (and heavier) due to their non-ovalized interiors, tend to also have inferior clamping points or mount strength, with bonded clamps that can and will fail even before the post itself does. The Thomson has one of the best clamps in the industry. It is a very strong post.
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Old 05-26-11, 01:41 PM   #10
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As stated, Thomson Elite.
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Old 05-26-11, 01:45 PM   #11
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Kent Eriksen makes a very nice looking titanium seatpost, but it's darned pricey. Andy Hampsten features it on his Strada Bianca model.
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Old 05-26-11, 03:45 PM   #12
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The Thomson is a great post, I have one on my super bling randonneuring bike and it's never failed me. But for less than half the cost I purchased an Easton EA30 2-bolt seatpost for my monstercross bike. This bike sees far worse than my brevet bike ever will, what with me riding on MTB trails not just pavement. I've got more post showing on the Easton than on the Thomson, and I've not seen any issues so far. (It's a short usage so far, of only a few months, but they've been a very harsh few months.) I can report back frequently, but as of now I don't have any concerns with this post being on the bike I plan to start racing in a couple months.
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Old 05-27-11, 02:20 PM   #13
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I would suggest that you start looking for a bike with a larger frame and larger diameter seat post so that less of the seat post is exposed. A bent seat post can and will fail at any moment.

The maximum stress on a seat post is at the point in enters the frame. The amount of stress is proportional to the force on the post (basically rider's weight plus shock loading) and the distance from the top of the saddle to the point where the seat post enters the frame. Reduce the distance from the top of the saddle to the point where the seat post enters the frame by half will half the stress on the seat post.

The wall thickness of the post has very very little effect on the peak stress - and thus the failing of seat post. The strength of tube (seat post) is proportional to the outer diameter raised to the fourth power minus the inner diameter raised to the fourth power. For example a 27.2mm seat post is over 30% stronger (and stiffer) than a 25.4mm seat post.
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Old 05-27-11, 03:30 PM   #14
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+1 on Thomson - I have also had good luck with the alloy FSA seatposts, a little bit cheaper but solid..
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Old 05-27-11, 11:43 PM   #15
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Quote:
Originally Posted by nfmisso View Post
I would suggest that you start looking for a bike with a larger frame and larger diameter seat post so that less of the seat post is exposed. A bent seat post can and will fail at any moment.

The maximum stress on a seat post is at the point in enters the frame. The amount of stress is proportional to the force on the post (basically rider's weight plus shock loading) and the distance from the top of the saddle to the point where the seat post enters the frame. Reduce the distance from the top of the saddle to the point where the seat post enters the frame by half will half the stress on the seat post.

The wall thickness of the post has very very little effect on the peak stress - and thus the failing of seat post. The strength of tube (seat post) is proportional to the outer diameter raised to the fourth power minus the inner diameter raised to treehe fourth power. For example a 27.2mm seat post is over 30% stronger (and stiffer) than a 25.4mm seat post.
I agree with what you write. Part of the issue is the frame is small for me and that I understand. BUT I have the rest of the bike set up exactly as I want. So I'll try the stronger post before canning the frame. Hope it's not "penny wise; pound foolish".
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