Originally Posted by
avhed
I noticed The Bridgestone RB-1 has a longer top tube: 57.5 cm. This is the longest I ever seen.most frames are 55-56 cm. Any out there with 56.5 or 57 cm?
Some current Soma/New Albion frames have a 57cm TT. I might do one of those if I do not get a vintage frame.
Most measure seat tube center to top. So your 56cm c-t-c may be what others call a 58cm size. Not unusual to see bikes this size with square geometry, where top tube center to center is very close to seat tube center to top.
The thread I posted earlier were frames well beyond square, like a seat tube of 53cm center to top, with a top tube of 58cm c-t-c.
On vintage road bikes, as sizes got larger, say 61cm CTT ST, top tubes didn't grow much. So less square.