Seat Post Slipping

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Re: Seat Post Slipping

Postby TomE. » June 24th, 2013, 1:48 pm

The out-of-roundness at the clamp may be a sign the clamp is not the correct size, or worn. If it's too big or too small, it will not tighten equally around the post. That would account for how badly your post is out of round, and perhaps not enough contact area to tighten correctly.
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Re: Seat Post Slipping

Postby AllMountin' » June 24th, 2013, 5:21 pm

I am having a frame warrantied for this exact issue. In my case, an excessive tolerance between post and seat tube caused a crack at the bottom of the split near the top of the seat tube. I found that if I removed the seatpost clamp, and inserted the seatpost, it would drop freely into the seat tube, and still have noticeable play at full insertion. This is not the case on my other frames.

For reference, my 30.9 posts(used a KS and a Spesh) measured 30.84(KS) and between 30.80 and 30.83(Spesh had a slight taper). This using a calibrated digital caliper w/.02mm accuracy and .01mm repeatability. With either post fully inserted, there was a gap at the bottom of the split at the top of seat tube. i could insert a dental pick into the gap between tube and post. You may want to check this. If there is a gap in between the post and tube, you may experience a similar frame failure later on.

Apparently the honing process used to clean up the seat tube isn't so precise.
--=Steve=--

Tom Robbins wrote:It's never too late to have a happy childhood.
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Re: Seat Post Slipping

Postby Kampfire » June 25th, 2013, 7:51 am

So I measured the seat tube on the frame.

Seat Tube: X:31.40mm, Y: 31.48mm

So idk if they usually are undersized slightly and when you put the post in the seat tube spreads?

I also emailed Thomson and waiting for a reply. Thanks for all the help guys.
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Re: Seat Post Slipping

Postby b_b » June 25th, 2013, 9:35 am

c0nsumer wrote:I'm just using some basic copper-based anti-seize for grease.

+1 Although I have no evidence this works better than grease I feel anti-sieze is generally preferable when lubrication is not needed or desired.
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Re: Seat Post Slipping

Postby jjc155 » July 17th, 2013, 6:58 pm

What about using some friction paste? Worked for me.

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Re: Seat Post Slipping

Postby Kampfire » July 18th, 2013, 2:51 pm

Issue fixed. They warrantied the ovaled seat post and the new one combined with a thomson clamp worked. Thanks for the help!
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