Thomson post slips even with tacx

[Ufgators]

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

[Devon]

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.

[Ufgators]

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.

[Ufgators]

I forgot to add I weight 155 pounds

[Devon]

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?

[MajorMantra]

Could be your torque wrench is out?

[Rick]

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

[Ufgators]

Should I try more clamping force? Say 6.5nm?

[Devon]

Should I try more clamping force? Say 6.5nm?

I'd personally check the clamp first.

[Ufgators]

Should I try more clamping force? Say 6.5nm?

I'd personally check the clamp first.

What do I look for in defective clamp?

[Devon]

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.

[thisisatest]

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

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[ghisallo2003]

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.

[1415chris]

If the Masterpiece is not robust, nothing is robust

[sungod]

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