Seat Post Slipping

[old bell]

I can't get my seat post to stay where I want it.
Its a carbon post in a Ti frame. I have cleaned the post and the tube and I crank the bolt to 8Nm, only 5Nm advised.
Any advice as to what I should do would be appreciated.

 

[Tim Hall]

Carbon assembly paste. Adds scientific friction to your shiny bits. Like this. (other manufacturers and retailers are available)

 

[old bell]

Thanks Tim. Although I hadn't heard of this stuff before the problem must be fairly common.
I have now ordered a tube.

 

[Broughtonblue]

I had same problem on my bike, although not carbon. LBS gave me some paste as previously mentioned, jobs a good un!

 

[02GF74]

if the carbon paste does not hold the post in place, I have another thing you can try.

 

[young Ed]

if the carbon paste does not hold the post in place, I have another thing you can try.

what, what?
maybe a little plastic shim might just work?
Cheers Ed

 

[02GF74]

no, not that. pretty sure I have posted this on here already so please do a search - i cannot be bothered right now to post the photo.

basically what I found happens is that as you do up the clamp, the open ends of the clamp start to bend so the force is not going in to tightening the post but bending the clamp!. you can see this as the open ends are no longer parallel.

what I did was to put a washer (thickness carefully selected) in the gap so the outer part of the open ends meet the washer and as the bolt is further tightened, the inner part of the open ends are forced together thus clamping the post.

hmmmmm ^^^^ if that doesn't make sense, I'll dig out the photo.

 

[02GF74]

re: shim - it should be impossible to fit a shim around the post as he gap is too small - unless your post is the wrong size - I assume you have correct diameter post??!??!?!?!?!

 

[PatrickPending]

same combination, same problem, paste worked for me!

 

[ayceejay]

There is a gap in your frame at the top of the seat tube right? and there is also a gap in the clamp? you no doubt have these together at the back of the seat seat tube, now turn the clamp 180 so that its gap is opposite the frame gap and tighten to 3nm, Suck it and see.