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Thomson post slips even with tacx
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Author:  Ufgators [ Thu Jun 13, 2013 1:31 pm ]
Post subject:  Thomson post slips even with tacx

I have a Parlee z0 fitted with the proper size Thomson masterpiece seat post and I notice that the post slips a
Couple millimeters per a 2 hour ride with 6nm of force on the clamp and a generous coat of carbon paste. Any suggestions? Thanks

Author:  Weenie [ Thu Jun 13, 2013 1:31 pm ]
Post subject:  Thomson post slips even with tacx


Author:  Devon [ Thu Jun 13, 2013 1:37 pm ]
Post subject:  Re: Thomson post slips even with tacx

May be a silly question but are you 100% sure it's the right size post? Should be 31.6mm

Is the post/inside of the seat tube worn at all?

How much do you weigh?

A quick/easy temporary fix would be to wrap the inserted end of the post in a thin layer of electrical tape.

Author:  Ufgators [ Thu Jun 13, 2013 1:51 pm ]
Post subject:  Thomson post slips even with tacx

alexh wrote:
May be a silly question but are you 100% sure it's the right size post? Should be 31.6mm

Is the post/inside of the seat tube worn at all?

How much do you weigh?

A quick/easy temporary fix would be to wrap the inserted end of the post in a thin layer of electrical tape.


Just measured it with digital calipers. The post measure 31.6 millimeters so probably within tolerance. The post isn't worn and the frame is new.

Author:  Ufgators [ Thu Jun 13, 2013 1:51 pm ]
Post subject:  Thomson post slips even with tacx

I forgot to add I weight 155 pounds

Author:  Devon [ Thu Jun 13, 2013 1:54 pm ]
Post subject:  Re: Thomson post slips even with tacx

I see no reason why it should be slipping in that case, unless there is an issue with the clamp? Try some threadlock/a new bolt maybe?

Author:  MajorMantra [ Thu Jun 13, 2013 2:08 pm ]
Post subject:  Re: Thomson post slips even with tacx

Could be your torque wrench is out?

Author:  Rick [ Thu Jun 13, 2013 2:19 pm ]
Post subject:  Re: Thomson post slips even with tacx

There has to be something else going on here. There is nothing about a Thomson seatpost that should allow unusual slip.

Author:  Ufgators [ Thu Jun 13, 2013 2:33 pm ]
Post subject:  Thomson post slips even with tacx

Should I try more clamping force? Say 6.5nm?

Author:  Devon [ Thu Jun 13, 2013 2:48 pm ]
Post subject:  Re: Thomson post slips even with tacx

Ufgators wrote:
Should I try more clamping force? Say 6.5nm?


I'd personally check the clamp first.

Author:  Ufgators [ Thu Jun 13, 2013 2:53 pm ]
Post subject:  Thomson post slips even with tacx

alexh wrote:
Ufgators wrote:
Should I try more clamping force? Say 6.5nm?


I'd personally check the clamp first.


What do I look for in defective clamp?

Author:  Devon [ Thu Jun 13, 2013 2:57 pm ]
Post subject:  Re: Thomson post slips even with tacx

Ufgators wrote:
What do I look for in defective clamp?


Shearing of the bolt/nut, or the clamp may be slightly too large for the frame and therefore unable to provide suitable clamping force.

Author:  thisisatest [ Thu Jun 13, 2013 3:25 pm ]
Post subject: 

Grease between the clamp and frame. Grease bolt threads fully, and under the bolt head. As before, Tacx paste on post to frame.

Sent from my EVO using Tapatalk 4 Beta

Author:  ghisallo2003 [ Fri Jun 14, 2013 8:24 am ]
Post subject:  Re: Thomson post slips even with tacx

I have always found that the Masterpiece posts are marginally smaller than the normal posts from Thomson. I wonder if the extra machining takes a small amount from the overall diameter. I know it is not the principle of WW, but if the torque is correct and the clamp ok, I would try another Masterpiece to see if it is a case of upper-lower tolerances, and then think about a non-Masterpiece. The weight savings are modest compared to having a robust seat fitting.

Author:  1415chris [ Fri Jun 14, 2013 11:20 am ]
Post subject:  Re: Thomson post slips even with tacx

If the Masterpiece is not robust, nothing is robust :wink:

Author:  Weenie [ Fri Jun 14, 2013 11:20 am ]
Post subject:  Re: Thomson post slips even with tacx


Author:  sungod [ Fri Jun 14, 2013 11:25 am ]
Post subject:  Re: Thomson post slips even with tacx

i had a similar problem with my ax europa post

6Nm, maximum rated torque - wrench checked against calibrated one at work
clamping bolt/nut threads clean and lubed
inside of seat tube degreased
the post is a tight fit

tacx paste didn't solve it - pink paste

finish line paste didn't solve it - white paste with gritty feel

but a mix of the two pastes did, at 6Nm the post no longer slips, been ok with this method for 3 years now

have to reapply paste mix any time i remove/refit the post, i.e. after boxing the bike for travel, otherwise it will slip without fail

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