Thomson Elite Seatpost WILL NOT stay put

Keeps slipping down a few mm every time i do a few miles.
Obvious q, is it the correct size? I've checked and double checked and it is 100% the correct size.

Grease in the seat tube a possible answer?

Grease in the seat tube a possible answer?

Replace grease with carbon paste.

Grease in the seat tube Assembly paste and a torque wrench a possible answer?

Yes.

Jinx!

What frame do you have?

@Scilly.Suffolk & @M_V — Problem is, i'm not using a Thomson clamp as the frame has one built in. I've literally tightened it as much as it will go without breaking.

I've used assembly grease too and still no joy.

@Pifko — Gorilla Hattarra... Def 27.2, as is the seatpost

Thomson seatposts are known for being a bit more slender than stated. I had the same issue with my Serotta. Luckily I could change to a slightly beefier clamp than came with the bike and problem was resolved. When I looked into the problem the most frequent solution (after better clamp) was as suggested - carbon assembly paste. Are you using normal grease or carbon specific? Also have you greased (not assbembly pasted) the bolt on the seatpost?

@dancing james — Ta. I used the tinniest amount of this > http://www.cyclesurgery.com/pws/UniqueProductKey.ice?ProductID=CFEN001500

Guessing Carbon Paste is my next step.
Re: the seatpost bolt — No. havent greased it. Not sure that would help as i seem to be reaching the maximum tightness possible and then it just stops. Never had a problem with my old Easton Seatpost. (for sale in the classifieds btw)

cyclesurgery.com/pws/UniquePr­oductKey.ice?ProductID=CFEN001500

Is just grease.

Get some carbon paste (incidentally I think the Park stuff is "carbon and alloy assembly paste" or something similar) in there and I bet it'll stop slipping.

Gotcha. Didn't make the distinction between the two. Will give it a crack. Ta

When I had a slipping Thomson, I used toothpaste. Mmm minty; worked fine.

You will once you apply it.

The carbon (and alloy) paste will feel quite granular which is why it helps with the grippiness.

For sure... I meant I hadn't previously realised there was a difference until you pointed it out ;)

Chaps, big thanks for the tips. Carbon Assembly paste is working a treat ;)

Problem is, i'm not using a Thomson clamp as the frame has one built in. I've literally tightened it as much as it will go without breaking.

If you overtighten it, you'll deform the frame and it won't tighten properly any more. Don't do that.

Make sure the bolt thread and head are greased so friction doesn't give you an inaccurate torque setting.

See post above yours ;)