Seat Post Slipping

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Seat Post Slipping

Postby Kampfire » June 24th, 2013, 10:08 am

So I have been having this non-stop *beep* of my seat post dropping while riding. I have a 2012 Niner One9 with a niner seat clamp and thomson elite seat post. The issue has been around mainly from the start. The initial issue was creaking and slipping. So i greased under the seat clamp and tube and that fixed the creaking issue. Now after riding say, 1 lap of Cannonsburg (5 miles) my seat post drops about 7-10mm. The longer I ride the more it drops. I've tried grease on the seat post (thin layer and needed so it won't creak), carbon paste, and just recently electrical tape just above the clamp on the seat post to kind of wedge it to stop. None of these items worked. Anyone have a tips/tricks to try?

Thanks,
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Re: Seat Post Slipping

Postby c0nsumer » June 24th, 2013, 10:15 am

Sounds like you need to tighten it more.
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Re: Seat Post Slipping

Postby Kampfire » June 24th, 2013, 10:17 am

I guess I'll take a torque measurement next time I do it but, pretty much tighten it has hard as possible with a regular allen. Too the point where i've had to replace the bolt with a higher grade version than the stock bolt. I'm afraid if i go any tighter its just going to yield the threads on the clamp.
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Re: Seat Post Slipping

Postby KLydesdale » June 24th, 2013, 10:23 am

You might want to check the diameter of your seatpost to see if it's on the smaller end of tolerance. I had problems like that with a Thomson post slipping on one of my old bikes and when I measured it with high accuracy vernier calipers, it turned out the post was outside Thomson's manufacturing specs on the low side. Thomson sent me a replacement post that was more toward nominal diameter and my slipping problems went away.


Have you used any other posts with the same frame? That's how I suspected the Thomson post was under-sized. It just felt like it had more play in it when inserted compared to other ones I had that fit the same frame.
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Re: Seat Post Slipping

Postby meangreen » June 24th, 2013, 10:49 am

Thomson sent me a replacement post that was more toward nominal diameter and my slipping problems went away

^THIS^

But if the post measures OK, I would go with a beefier clamp like a salsa lip-lock/thompson etc.
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Re: Seat Post Slipping

Postby c0nsumer » June 24th, 2013, 10:52 am

meangreen wrote:
Thomson sent me a replacement post that was more toward nominal diameter and my slipping problems went away

^THIS^

But if the post measures OK, I would go with a beefier clamp like a salsa lip-lock/thompson etc.


This surprises me, but it's good to hear. Thomson calls out the tolerances (+0, -0.03) on their site, so I'll have to check mine in the future.
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Re: Seat Post Slipping

Postby Kampfire » June 24th, 2013, 10:53 am

I'll take home my calipers from work and measure. The tolerance from Thomson's website say +0.0/-0.03mm. Thats crazy tight!

I had a Niner RDO Carbon seatpost on it when I first bought the bike. It lasted all of about 3 months and cracked right at the seat clamp. It slipped and creaked as well.
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Re: Seat Post Slipping

Postby c0nsumer » June 24th, 2013, 10:57 am

Kampfire wrote:I'll take home my calipers from work and measure. The tolerance from Thomson's website say +0.0/-0.03mm. Thats crazy tight!

I had a Niner RDO Carbon seatpost on it when I first bought the bike. It lasted all of about 3 months and cracked right at the seat clamp. It slipped and creaked as well.


How close are you to the minimum insertion line? If you're really close that could have the seatpost wobbling and possibly slipping a bit more...
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Re: Seat Post Slipping

Postby Kampfire » June 24th, 2013, 10:58 am

I have the 400mm seatpost. I'll double check that as well. I'm thinking I have about 50mm left before the max line.
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Re: Seat Post Slipping

Postby c0nsumer » June 24th, 2013, 11:02 am

Kampfire wrote:I have the 400mm seatpost. I'll double check that as well. I'm thinking I have about 50mm left before the max line.


That seems like plenty to me.

On my El Mariachi Ti I have a 410mm Thomson with a Salsa clamp and it was slipping until I tightened it a little more than I thought sane. Now it's stayed in place for... 500-ish trail miles? (Salsa doesn't publish a torque spec.) I've got about 50mm beyond the minimum insertion line on mine as well, and I'm just using some basic copper-based anti-seize for grease.
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Re: Seat Post Slipping

Postby Kampfire » June 24th, 2013, 11:55 am

OK, here are the measurements my 31.6mm seat post. I did 3 sets of measurements. Top about 50mm below the saddle. At the clamp point and at the base of the post. X is parallel with the frame and Y is parallel with the handlebar.

Top: X: 31.67mm Y:31.68mm
Clamp: X: 31.30mm Y: 32.01mm
Bottom: X: 31.52mm Y: 31.56mm
*Measurements taken with Mitutoyo digital caliper.

So obviously the clamp has ovaled the seatpost. Looking at the bottom measurement it may appear the seatpost was undersized from the factory?
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Re: Seat Post Slipping

Postby c0nsumer » June 24th, 2013, 12:08 pm

Kampfire wrote:OK, here are the measurements my 31.6mm seat post. I did 3 sets of measurements. Top about 50mm below the saddle. At the clamp point and at the base of the post. X is parallel with the frame and Y is parallel with the handlebar.

Top: X: 31.67mm Y:31.68mm
Clamp: X: 31.30mm Y: 32.01mm
Bottom: X: 31.52mm Y: 31.56mm
*Measurements taken with Mitutoyo digital caliper.

So obviously the clamp has ovaled the seatpost. Looking at the bottom measurement it may appear the seatpost was undersized from the factory?


I can tell you that when I emailed Thomson a silly question someone replied to me from their phone within a couple hours. They are quite responsive. I'd contact them and see what they say.
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Re: Seat Post Slipping

Postby SteveF » June 24th, 2013, 12:44 pm

The frame's seat tube could be off-spec, too-oversized or ovalized. Simple fix: I had a Salsa post/Gunnar frame combo that slipped no matter what so I put a piece of that heavy duty clear vinyl frame protector tape on the post so it overlayed above/below the seatclamp area by a couple of inches each way and it never slipped again...
Sometimes the squeaky wheel gets replaced.
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Re: Seat Post Slipping

Postby MediumRB » June 24th, 2013, 12:51 pm

I'd blame the seat clamp and seat tube (i.e. Niner's fault). If you can get a measurement in there, then that may illuminate the problem.
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Re: Seat Post Slipping

Postby shoffman » June 24th, 2013, 1:37 pm

I had numerous seat post slippage problems with a couple Niner Air 9's. I tried multiple approaches.... more robust clamp, cleaning the seat post, greasing it, using sidewalk chalk (per Niner's recommendation), etc. and couldn't figure out the problem until I spent some time discussing this with a tech rep at Niner. I had a Thomson Elite setback seat post and had all but a couple inches of a 410mm post exposed. He recommended going to a straight seat post and make up the difference on the handlebar stem.

I followed his recommendation, and have never had another issue with slippage... none. I'm guessing that having a large amount of exposed post and having it in a setback position probably put too much stress in that area.
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