Originally Posted by
fuzz2050
It's not the second digits that determine class, it's usually the first. 5xx, 6xx and 7xx are all touring bikes. The 520 needs no introduction, the 720 is even more epic, and almost impossible to find. I have a 610 that has chainstays longer than even the Long Haul Trucker, and the 600 I posted earlier is still rather touring in geometry.
4xx are usually of lower quality, although I would kill for a 420L for my girlfriend (do you know how few mixtes were made with nice tubing?), although they were still quite nice. They had a more generic 'sport touring geometry, even the 420's
I think X00's were framesets that were sold without being built up. Eh, it's hard to find a pattern in the madness, just bookmark
http://www.vintage-trek.com/
No, Skyrocker had it right. The first digit indicates the frame material "5xx" used Ishiwata 022 tubing, 6xx used Reynolds 531 main tubes and pre-fab Ishiwata or Tange forks and rear triangle, 7xx was all Reynolds 531 brazed in Waterloo, 9xx was all Columbus (SL or SP depending on frame size) brazed in Waterloo, and 1xx was Reynolds 753 brazed in Waterloo.
The second digit indicated the frame geometry: 0 or 1 was a "sports touring" geometry, 2 was touring geometry, 3, 6 or 7 was racing geometry. The last digit was just a model designation.
The "n00" frames were bare framesets, but IIRC this designation was dropped in the early 80s so that a single, terminal 0 indicated a bare frame. E.g. a "977" was a Columbus tubed, racing geometry frame built with a Campy Super Record group, while a "970" was just the bare Columbus frame and fork.