Angel,
There's several possibilities.
The worst case scenario is that the seat tube and lug warped from excess heat while brazing on the seat stays.
The top of the seat tube goes out of round or the seat tube bulges inside the lug or both. I've seen this problem on many frames, even from top name builders.
There are several easy fixes that should be done prior to painting. The seat tube should be checked for size and roundness. Almost all seat tubes need to be reamed to size.
If the seat tube is only slightly out of round then light reaming will take care of it. Otherwise a round steel tool or series of tools need to be driven into the seat tube to round it out and then reamed to proper size.
The most likely situation is the builder used heavier walled Columbus SP tubing instead of SL. That's a common practice for increased rigidity with many 60+cm Italian frames.
Seat tube diameter = 28.5mm (approximate) Columbus SP wall thickness = 0.7mm x 2 = 1.4mm (approximate) 28.5mm - 1.4mm = 27.1mm or a 27mm seatpost but... it's going to be a tight fit so a 26.8mm is used instead
On less expensive frames it's easier for builders to use a smaller seatpost than spend time correcting the problem.
Chas. Colerich Oakland, CA USA
-----Original Message----- From: Angel Garcia Sent: Fri, Aug 14, 2009 6:23 am Subject: [CR] Early 80s CIOCC with 26.8 seatube?
I recently received the following inquiry regarding a 1980's CIOCC. Anyone have details, or speculate, on the tubeset CIOCC used? Or, familiar with this model? ::
I recently purchased an (wE believe) early 80s CIOCC Frame World 1977 Model Signed at end of top tube by Giovanni Pelizzoli White Ciocc Lettering w/ Multi colored C & Vertcal in white CIOCC on Headset. Before it was stripped It had NR Head BB Front & Rear Derail & Seatpost w/ Campy GS Crank & Brake Set.
All the lug work & CIOCC signature white trim is correct even fork braces match an original MOCHBA 80 that i have compared. It even has the American Importers LOGO on back brake bridge ?
Question is The seat Tube appears to be 26.8 Diameter Most believe it should be 27.2? It has been checked w/venier & by my LBS mechanic & my SR 27.2 does not fit but a 26.8 at LBS seems to fit perfectly. There is a proper gap in tubing where seatpopost bolt goes so I don't think it has collapsed any ???
Any idea to what tubing it might be? To your knowledge was there Columbus SL or could Columbus have given pelizzoli something custom in late 70s early 80s in 26.8 or just AELLE ? It is a large frame Stamped 60 measures 61 c to c might they have used something "Double Walled" for straight in such a large frame?
Angel Garcia
Long Valley NJ