Thomson post slips even with tacx

Discuss light weight issues concerning road bikes & parts.
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DMF
Posts: 1062
Joined: Sat Dec 06, 2008 10:14 am
Location: Sweden

by DMF

I've never run across a Thomson post, Masterpiece or otherwise, that doesn't drop down by it's own weight into the seat tube unless there is a clamp present. 'Snug' is not the word I'm looking for here... If you ask me they're all just very slightly undersized, and the ribbed surface for what friction concerns is just useless - polished and smooth is the way to go (I.e Tune Starckes, USE Alien, ...)

Google around for slippage problems with Thomsons in Ti-frames, quite a common issue...

iamalex
Posts: 209
Joined: Sun Oct 30, 2011 5:25 pm
Location: London, UK

by iamalex

I've had a few slipping issues with Thomson Masterpiece/Elite posts though this was with Ti frames rather than carbon.
One Masterpiece was actually outside of the published tolerances and refunded. Working solution for me for the others: greased inside of clamp, Finishline FiberGrip paste on post (librally applied) and a Salsa Lip-Lock clamp. I had to torque the clamp a fraction over spec. but since then the bike has been abused and no slipping so far. In my case the clamp seemed to make all the difference over some generic and Thomson ones. Good luck.

by Weenie


Ufgators
Posts: 220
Joined: Sun Sep 27, 2009 4:28 pm

by Ufgators

Could my problem be that I am using the clamp with the bolt side facing the front of the bike or does it really matter?

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tommasini
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Location: Central USA
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by tommasini

A clamp with the bolted section away from the slot in the frame was originally targeted for the early generations of more fragile carbon posts......the offset slot clamps have helped there a lot. So if you are trying to clamp that aluminum post (which isn't all so super fragile) I'd suggest having the clamp bolt/slot line up with the slot on the frame.....that frame slot is typically in the rear but not always.

rowdysluggins
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Joined: Tue Apr 27, 2010 2:36 am
Location: Taylosville, Utah

by rowdysluggins

Ufgators wrote:Could my problem be that I am using the clamp with the bolt side facing the front of the bike or does it really matter?

Maybe (I doubt it), but I usually line up the bolt (split part of the clamp) with the split in the seat tube. Less friction to overcome when clamping.
Also, if that doesn't solve the problem, I would definitely try another seat clamp. I don't know what clamp you have but KCNC makes a nice light weight alu clamp that works well (as do many others). In fact, if you are having problems you might want to try a non WW clamp with a wide clamp area just to eliminate that as a possibility.

Tom-s
Posts: 144
Joined: Sat Apr 26, 2008 10:44 pm
Location: Holland/Belgium

by Tom-s

I've had the same problem with my masterpiece in my litespeed.
How i solved it:
- Undo the clamp to check where it has the most play between frame and seatpost.
- Get paste for carbon parts and a piece of paper.
- Place the paper on the inside of the frame using the carbon paste, and put carbon past all over the part of the frame that meets the seatpost.
- Secure the paper under the seatpost clamp for a small bit.
- Now you will notice it's a lot harder to mount the seatpost.
- Mine doesn't slip anymore with only 3.5-4Nm on the tiny carbon clamp.
- (i needed 2 pieces because there was a lot of play front to back).

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marcelflash
Posts: 83
Joined: Mon Sep 01, 2008 5:07 pm
Location: Zwaag Nederland

by marcelflash

try sanding the post around the clamp just to make it rough.
sometimes the surface of seatposts are too slippery because of paint or finish

jooo
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Joined: Wed Feb 02, 2011 3:48 am

by jooo

I don't think it's been said yet, but is your ST actually oversize?

Tom-s
Posts: 144
Joined: Sat Apr 26, 2008 10:44 pm
Location: Holland/Belgium

by Tom-s

I have 2 Thomson masterpiece's. Both are a loose fit compared to other seatposts.

Ufgators
Posts: 220
Joined: Sun Sep 27, 2009 4:28 pm

by Ufgators

I think problem solved. I flipped collar around, increased tension to 7nm per Parlee recommendation and used a tiny bit of blue loctite which might not have been necessary but didn't want to chance it. The collar bolt kept loosening.

User Name
Posts: 596
Joined: Tue Jun 07, 2005 3:32 pm

by User Name

ghisallo2003 wrote:I have always found that the Masterpiece posts are marginally smaller than the normal posts from Thomson.
me, too. I've got 3 older ones, and they started slipping after a couple of years.

User Name
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Joined: Tue Jun 07, 2005 3:32 pm

by User Name

I hate using shims, but I do. There's something a bit cheap and crappy about having to put a shim on an expensive bike.

Larger clamps with 5mm-head bolts seem to generate much more torque than 4mm bolts. I've got some post/frame combinations that wont work at all with a 4mm bolt, but work fine with 5mm bolts.
Last edited by User Name on Sun Jun 16, 2013 6:47 pm, edited 1 time in total.

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Horze
Posts: 145
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Location: Transilvania

by Horze

Ufgators wrote: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


Don't use a generous amount of paste. As you'll eventually get a lubrication effect out of it. Tacx is quite greasy.

Thomson posts already have graduations in the tube surface to increase contact area (hence friction) with the inner wall of the seat tube. You can install the post without compound. But if you apply too much paste, you may effectively be smoothing out the surface.
7x Forum Racing Ban Champion.

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