Originally Posted by
Andy_K
It's actually even more unusual than that. The seat tube and down tube are tapered. They're both 28.6 at the top but around 36 mm at the bottom bracket. I believe this is standard for Serottas of this period (~1987). If I understand correctly, this is the "Colorado Concept" tubing that is (I think) unique to Serottas.
Probably a good chance Dave Kirk built the frame
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