Esoteric question about vintage Columbus tubing

[Kommisar89]

Not sure why this though even occured to me today but I was wondering...

(Be forwarned that I know less than Jack about frame building so you might want to keep it simple...)

I've gathered from these forums that the older Columbus tubing (mid-70's and earlier) that was simply labeled "Tubi Rinforzati Accacio Special' would be the equivalent of the later designated SL or SP depending in the size and purpose of the frame with SL used for small to medium sized frames and SP on larger frames and mixtures in between. So with my old frame being 58.5cm C-C, I figure it's kind of in between. My assumption (probably based on pure speculation) is that the tubing thinkness is internal and the external diameter would be the same while the internal diameter would be smaller to allow components to fit regardless of which tubing was used. Of course about the only place I could measure that would be the seat tube. And then I though, hmmm, I don't even know where you might use SP vs. SL (i.e. - main tubes, stays, only specifc tubes) so I don't even know if that would be valid. So is there a way to tell the difference between SL and SP?

[Six jours]

IIRC the main tubes for SL were .9/.6/.9 and SP was 1.0/.7/1.0. You are correct in that O.D. is consistent between the different tubes. And the inside of the upper part of the seat tube will have been reamed to 27.2 regardless of the tubing, so that won't help. AFAIK the first tubes to get switched from SL to SP, as frame size/stiffness requirements increase, were/are the down and seat tubes.

The only measuring method I can think of is to find a largish ball micrometer that can be fit into the bottom bracket shell to measure the thickness of the seat tube or down tube butt.

HTH!

[dookie]

columbus tube specs (http://middlepath.gotdns.com/bikes/columbuschart.htm)

[bikejack]

The sticker 'Tubi Rinforzati Accacio Special' is guaranteeing the tubing is Columbus, it was a replacement sticker issued to Columbus builders for use on repainted or repaired bikes or bikes with a mixture of tubes as often found in larger size frames.