Broken Carbon Fibre seat post

Yow!! Be glad you caught it before it broke. Instant core sample.

it could of been a real pain in the butt if you didn,t find it.
but no it should not have happened pole might have been pores.

rnb930 said:

Got the shock of my life today on realising that the reason my seat suddenly has lateral movement is that the seat post is almost completely sheared through. The post has a split about 3/4 of the way through, just above where the post meets the frame.

It is a SELCOF seat post, 2 years old and I have never taken it off the bike nor mucked around with it since taking delivery of the bike. The bike is a Wilier frame with Campy Centaur group set.

Can anyone cast any light on this ,, are these things supposed to break ?!?

it could of been a real pain in the butt if you didn,t find it.
but no it should not have happened pole might have been pores.

rnb930 said:

Got the shock of my life today on realising that the reason my seat suddenly has lateral movement is that the seat post is almost completely sheared through. The post has a split about 3/4 of the way through, just above where the post meets the frame.

It is a SELCOF seat post, 2 years old and I have never taken it off the bike nor mucked around with it since taking delivery of the bike. The bike is a Wilier frame with Campy Centaur group set.

Can anyone cast any light on this ,, are these things supposed to break ?!?

As for the seat post, you say you have never adjusted is since delivery. Maybe it might have been overtightened prior and was just waiting for the right amount of pressure from sitting on it ?
Carbon fiber seat posts have a incredible amount of strength that rivals most special performance metals whilst saving weight giving it a clear advantage as a performance material, but a number of things may have been at fault such as the aforementioned overtightening of the seat post collar as that will have caused an extreme amouunt of lateral pressure which the post wasn't designed for that purpose. Also the roll up of the carbon fiber has its flaws as well. From the factory if the manufacture is flawed (resin not setting properly or too much or too little, etc) it will leave the structure compromised.

rnb930 said:

Got the shock of my life today on realising that the reason my seat suddenly has lateral movement is that the seat post is almost completely sheared through. The post has a split about 3/4 of the way through, just above where the post meets the frame.

It is a SELCOF seat post, 2 years old and I have never taken it off the bike nor mucked around with it since taking delivery of the bike. The bike is a Wilier frame with Campy Centaur group set.

Can anyone cast any light on this ,, are these things supposed to break ?!?

The seat post clamp could have been overtightened as leandro said. Also, consider that the top of the seat tube, or the clamp itself could have a sharp edge on it, rather than a smooth "relieved" bevel edges. Sharp edges will cut into the soft surface of the CFRP, setting up a notch which concentrated all the bending loads right where you don't want them.

Bottom line for me is that a seatpost is not a great application for CFRP due to the compression/bending loads, installation issues, and the repeated seat adjustments some riders do.

dhk2 said:

The seat post clamp could have been overtightened as leandro said. Also, consider that the top of the seat tube, or the clamp itself could have a sharp edge on it, rather than a smooth "relieved" bevel edges. Sharp edges will cut into the soft surface of the CFRP, setting up a notch which concentrated all the bending loads right where you don't want them.

Bottom line for me is that a seatpost is not a great application for CFRP due to the compression/bending loads, installation issues, and the repeated seat adjustments some riders do.

I would make sure that when you have a carbon seat post that the seat post clamp is set so that the slot on the frame is opposite the slot on the seat post clamp. I guess that the slot in the frame can damage the carbon when the seat post clamp slot is on the same side. I have seen 2 posts break in the same spot from having the clamp in this position

Thanks forum members for your advice and help ...

Today I took the broken post back to Richmond Cyclery, here in Melbourne. I have been completely satisfied with the pre and post sales service received from Grant and his team. Unfortunately - for all concerned - Grant was robbed over the weekend. Thieves who knew exactly what they were looking for got into the shop, and picked the best from his stock of high end cycling gear. Aussie cyclists pls take note - and be careful of any high end and low mileage second hand gear coming up that doesn't have provenance!

In spite of his troubles, Grant will take up the broken seat post with the rep fro whoever it who distributes Selcof, and I'll post the outcome. The post is a 31.4mm diamater, which I (now) understand is on the unuusal side, so I'm off the road while this is sorted. Grant told me he'd never seen this before. His guess was the collar that tightens the seat pot is the culprit (my guess too).

Thanks forum mebers for your comments. To answer a couple of issues raised in the responses to my post - the slit in the clamp doesnt align to any slit in the frame. The frame has 4 slits, and they are on the 45', or diagonal side. The clmap is tightened to the rear of the bike. I was sensitve to the clamp tightness when I undid the allen key holding this in place, and did not feel it had been overly tightened.

Thanks again,