Carbon Seat Post Slipping

[cool_hand]

Try something like this https://www.tredz.co.uk/.Fenwicks-Professional-Carbon-Assembly-Paste_101992.htm

Thanks. However, I'm already using Finish Line Fiber Grip Carbon Fibre Assembly Gel which is appears to be pretty much the same thing!

Moving the reflector band down wont stop the seat post slipping, it will just get pushed upwards.
I had this and used carbon paste and aligned the clamp with the cut-out on the seat tube and all is now well. It drove me mad.

So far the reflector appears to have held the post in place. Not the solution I want though.

 

[craigwend]

What make is the bike?

 

[newts]

Give the seat tube & the seatpost a good clean & degrease, their may be residue (under the fibre paste) on one of the mating surfaces causing the slip.

 

[Kingfisher101]

You can get those double seat post clamps? one bit goes round the post whilst the bit below goes round the seat post? What I'd try first is cleaning the inside of the seattube with a rag and the post and adding carbon paste to both, then tightening the clamp over the slot. Clean the clamp as well and grease the bolt.
If this didn't work, you could try making a shim out of a pop can and wrapping it round the seatpost to fatten it up a bit?

 

[YellowV2]

I had exactly the same problem with a new Enigma frame this summer. I made sure there was plenty of Carbon assembly paste on it and torqued to 8Nm up from the original 6.5, seems to have done the trick, it hasn't slipped since.

 

[cool_hand]

I had exactly the same problem with a new Enigma frame this summer. I made sure there was plenty of Carbon assembly paste on it and torqued to 8Nm up from the original 6.5, seems to have done the trick, it hasn't slipped since.

Do you know how long your post is? I've been fairly liberal with the paste but only went to 7nm. I don't remember it slipping on an alloy frame.

 

[YellowV2]

I’ts a Deda Superleggero and listed as 350mm long. I would refit it with extra paste and tighten to 8Nm and try that. I don’t think it’s an unusual problem with Carbon seatposts to be honest, I know of a few people who has had the issue in Carbon and Ti frames.

 

[figbat]

I wonder if it is to do with surface finishes? Perhaps the internal surface finish of a Ti frame tube is different to that of an aluminium or steel tube, offering lower static coefficient of friction.

 

[cool_hand]

I’ts a Deda Superleggero and listed as 350mm long. I would refit it with extra paste and tighten to 8Nm and try that. I don’t think it’s an unusual problem with Carbon seatposts to be honest, I know of a few people who has had the issue in Carbon and Ti frames.

I've swapped over to the original alloy seat-post which is 320 mm vs. the 200 mm carbon seat post – 6 nm no issues with slippage, that sort of indicates it's not the clamp that's at fault. I don't remember slippage on the alloy bike frame the carbon post came out of. I do have another alloy road bike so I could try a test to see if it slips in that frame. Have always admired the Deda Carbon seat-posts, very nice looking design.

I wonder if it is to do with surface finishes? Perhaps the internal surface finish of a Ti frame tube is different to that of an aluminium or steel tube, offering lower static coefficient of friction.

Sounds logical. Probably a combination of materials and short post. A longer post would no doubt help.

 

[Ajax Bay]

The frictional force (to hold the seat post up against gravity plus dynamic body weight) depends on compressive force, generated by the seat post clamp (metal frame) and the coefficient of friction between the two materials/surfaces.
These forces are confined to a centimetre at the top immediately below the seat clamp.
Length of seat post makes zero difference. Greasing the seat post before insertion might mean it'll be easier to get out when the time comes, but will reduce the coefficient of friction.

 

[T4tomo]

A longer post would no doubt help.

fixed it!

 

[cool_hand]

The frictional force (to hold the seat post up against gravity plus dynamic body weight) depends on compressive force, generated by the seat post clamp (metal frame) and the coefficient of friction between the two materials/surfaces.
These forces are confined to a centimetre at the top immediately below the seat clamp.
Length of seat post makes zero difference. Greasing the seat post before insertion might mean it'll be easier to get out when the time comes, but will reduce the coefficient of friction.

In all the Fiber Grip application videos I've seen they are always very liberal with the paste, it is not applied just to the clamping area but to the whole of the post . Fiber Grip creates friction between surfaces - larger surfaces equals more friction. Yes, the post will still need to be clamped but any additional friction created by the paste outside of the clamping area is not zero.

 

[Kingfisher101]

In all the Fiber Grip application videos I've seen they are always very liberal with the paste, it is not applied just to the clamping area but to the whole of the post . Fiber Grip creates friction between surfaces - larger surfaces equals more friction. Yes, the post will still need to be clamped but any additional friction created by the paste outside of the clamping area is not zero.

Why do you think this is then?
Its a wonder the whole bike isn't lathered in it.

 

[cool_hand]

Why do you think this is then?
Its a wonder the whole bike isn't lathered in it.

Of course they want you to use the paste up quickly as possible but this liberal application is not unique to the Finish Line video. All I'm saying is the paste is creating friction between the surfaces including surfaces outside of the clamping area.

 

[Biker BoB]

Rough the inside of the seat tube on the frame with a light glass paper