seat tube stress crack CF thoughts .
 

This is the area of the seat post on my Wilier that had the slight downward tearing in the carbon fiber. It simply started to sort of bend/tear at the seat post opening. I took a file and filed down past it, and this is what looks like now. My thought is that it is not fatal error or that the bike will explode, but I just wonder if it may start up again along that same line. The seat post sits all the way down and the forces I would think not be enough to do anything. I don't use this as my everyday riding bike but it really is a decent frame and I hate to say it is worthless now.
https://cimg3.ibsrv.net/gimg/bikefor...cf0c7d2f31.jpg

I can't follow if you are talking about a frame or a post or a mast.

Are you referencing a previous thread?

My bad not talking about earlier thread. I am talking about the frame not the post. This is the frame seat tube that is semi-integrated and the opening is normal so that when you tight the seat collar it gives just enough to clamp. The crack started to stress at the end of the opening. I simply file down past it just a bit. Hopefully this makes sense.

It's hard to tell what's going on from the photo.

Is there an alloy collar on top of a carbon seat tube that the saddle attachment slides down and clamps onto? And you cut a vertical slice out of it to get rid of a crack?

Try zooming out for a couple more photos.

Yes the alloy clamp is the collar. On the seat tube going down about 1.5 inches is an opening in the seat tube that is made in the frame. This allows the compression of the alloy clamp. This channel is made hat way in the frame. At the end of the vertical channel there was a small tearing of the carbon fiber that had began to crack and work further down.

5 to 1 odds the real issue is an undersized post.

This would cause the frame to ovalize when the clamp is tightened. So the first step is to double check that the post has a snug running fit in the frame.

I bring this up because finding and dealing with the cause is critical to the long term outlook.

In any case, the frame is safe to ride because the post is carrying the load down to where there's solid structure.

But, safe for you is different than safe for the frame. You need to find the cause, and should consider reinforcing the damaged area before the crack extends deeper.

How many inches of seatpost are in the frame?

FB you are spot on! On this frame I actually had a seat post get stuck. I had to have it drilled out at the machine shop. In trying to get it out i managed to move the seat tube at the top enough to get the crack going. What I have done now is add a seat post adapter 27.2 to 31.6. This allows a seat post of the 27.2 in the frame and to make it all snug I used some aluminum foil tape around the adapter, and an added layer to the outside of alloy clamp area. I believe now it is really snug and does not ovalize when I tighten the collar.

The normal opening on the seat post on this Wilier is 31.6. I had a 27.2 seat post already so that is why I just added the adapter to use in the frame. Actually, given it allows more independent layers of tubing I am hoping it might be better. The goal is as you say, not allow the seat post tube to have any real movement and potentially start cracking down again. That is why I filed down the crack till the end of it to relieve the stress and provide uniform channel. I am just unsure over time and riding how this might work out but I suspect nothing more will happen. In my case I can relegate it as an indoor trainer bike. I like the ride and fits me really well but truth be know I have 3 Habanero Titanium bikes I ride. I will not ride this much outside probably but I might at some point want to sell it and do not want any issues.

A few points.

Start by building up the OD of your shim slightly with paint or glue soaked paper to get a tighter (barely) running fit. The goal is to have the post so snug that nothing actually moves when the clamp is tightened. Also see if you can find a shim long enough to reach at least 1" below the top of the top tube, so it's well braced by the frame, not the cantilever. Lastly, turn the shim 180 degrees so the closed section is bracing the slot in the frame.

Also, CF is not like steel or aluminum, so the methods to stop crack propagation will be different, and unfortunately, it's more difficult to stop in CF because of the lack of ductility. I'd watch it closely, and if there's any hint of getting worse, I'd splint it with a CF patch. Not a glue on quick fix, but a proper splint bonded in place, preferably by an experienced framebuilder.

Semi integrated....