Fitting a carbon seat post

[Tel]

All this carbon stuff is new to me. Do I grease the pin? I've read about getting the torque right so I presume I don't want to just whack it up as tight as I can.

I'm fitting it to an old steel Reynolds 501 frame.

Thanks in advance for your help

 

[Steve Austin]

no grease. you could use some of the pace carbon composite paste if it starts slipping.

You are supposed to use a torque wrench, but i don't believe anyone who can be sensible to realise that you don't need to swing on the end of a scaffold pole to tighten a seatpost collar would ever need one.

 

[MartinC]

Using Carbon Paste is the best bet. Then you can just nip them up and you know they won't slip. Sometimes they don't, sometimes they do otherwise.

 

[mickle]

Make sure the seat lug has no burrs or sharp edges which might cause a high pressure zone, particularly the top rear edges and the sides of the slot.

 

[Tel]

Thanks for the advice guys.

I've done it, bloody hell it was tight. There was so much friction that the seat tube was too hot to touch! A 27.2mm came out but was only about 180mm long so there wasn't much post in the tube, my new one is 350mm so there is a fair bit extra in there, it was so tight that I considered cutting 100mm off but I persisted; in, out, in, out, each time a little looser. I reckon I must have lost a couple of kg in sweat. Perhaps the internal quality of the 501 isn't all that, I did open up the top of the tube and checked for burrs, etc as you suggested Mickle thanks.

Now it's all fitted I pinched the seat bolt up but probably could have left it off And I've got that little bit of extra height that I've been in need of and they're supposed to offer a little more comfort too aren't they? Oh and a whole 80g saving over my old post

 

[montage]

How much of the post is sticking out above the frame? I've heard some nasty stories about long carbon posts snapping - easy to prevent, simply put some metal tubing on the inside where you clamp the post.

 

[02GF74]

Thanks for the advice guys.

I've done it, bloody hell it was tight. There was so much friction that the seat tube was too hot to touch! A 27.2mm came out but was only about 180mm long so there wasn't much post in the tube, my new one is 350mm so there is a fair bit extra in there, it was so tight that I considered cutting 100mm off but I persisted; in, out, in, out, each time a little looser.

sounds like you have a mountain bike post - much longer - than a road bike.

I would guess the road bike was never meant to have so much seat post inserted so only the part near the end has been cleaned/machined internally, also being a steel tube, the part that was not covered by the post would have got rusty so the hole would have gotten smaller.

In my opinion you should have return the post and got a shorter one or cut it to length, as you suggested.

After a few months of it being in place, I would bet it will be even harder to remove.

 

[02GF74]

simply put some metal tubing on the inside where you clamp the post.

yep - I use a short length of copper pipe to stop my CF post from slipping - I had tightened the clamp to the point where I could see the varnish crack - i.e. a touch too tight. no other damage mind.

It is unlikely that the pipe will be same diameter, but you can cut a slot and file it down so the diamter is correct - the butt joint should be enough to stop the pipe from collapsing - I cannot recall if I did this or not but have done so in the past with success.

The pipe only needs to be 20 mm long and pushed to the point there the clamp is.

 

[montage]

yep - I use a short length of copper pipe to stop my CF post from slipping - I had tightened the clamp to the point where I could see the varnish crack - i.e. a touch too tight. no other damage mind.

It is unlikely that the pipe will be same diameter, but you can cut a slot and file it down so the diamter is correct - the butt joint should be enough to stop the pipe from collapsing - I cannot recall if I did this or not but have done so in the past with success.

The pipe only needs to be 20 mm long and pushed to the point there the clamp is.

This pipe will
1 - help prevent overtightening and
2 - spread the pressure. Where the carbon seatpost is at an angle, alot of pressure is place on the rear end of the clamping point - if you put a pipe(I would go for slightly longer than 20mm for this circumstance) up the middle of the post as 02GF74 describes then this will spread the pressure BUT you need to cut the top at an angle - by this I mean if you were sawing a pipe in half, instead of taking the shortest route accross the diameter cut at a large angle so that the top of the top has a long slope to it ... if you just have a standard pipe with the top cut accross the diameter than this doesn't spread the pressure, just moves the problem from the clamping point to where the pipe ends.

Does that make sense? :s

 

[mickle]

Chop it to length or it'll get stuck in there.

Inserting extra material is a waste of time. It wont increase the strength of the post unless it's a very tight fit and/ or bonded in.

 

[montage]

Chop it to length or it'll get stuck in there.

Inserting extra material is a waste of time. It wont increase the strength of the post unless it's a very tight fit and/ or bonded in.

but it will disperse the pressure

 

[NickM]

A carbon fibre seatpin in a steel seat tube which has not been specifically reamed to fit sounds like potential trouble to me...

 

[Tel]

Erm, starting to worry about this a bit!

There's about 150mm (6") or so of post sticking out. I'm thinking about removing it and cutting it down to about 280mm perhaps less, suggestions?

I'd also like to invest in some of that special Tacx grease stuff.

Hope I can get the post out now...

 

[mickle]

Nothing to worry about at all. Do chop a bit off before it sticks itself in there forever, do remove any sharp edges from the seat lug, do lather it in some gunge.
It's a mountain bike post designed to handle big fat barstewards and big impacts with a foot of post above the frame, your skinny white ass with six inches sticking out aint gonner break it.

 

[Tel]

Thanks Mickle