Originally Posted by
Jack Tone
I had a mountain bike with the same problem (my seat post was too short). Had it welded and it was fine. That crack looks a lot longer than just where the grease is showing.
It's tricky to inspect, the shoreline of the weld bead is a bit proud of the seat tube and the crack is right along it. Hard to tell whether there's a crack or just the edge of the weld bead - I had thought about trying a fluoro penetrant inspect kit on it but given what the weld shoreline looks like I don't know if I could trust the results. Makes it difficult to commit to a relatively costly repair when I don't know the full extent of the issue. And the frame is worth maybe like $100 even if it wasn't cracked.
This is an older picture, I rode it a few months more and the crack propagated on each side to about double the length pictured. I stop drilled it with a 1/16" bit but got a new frame shortly after.