Originally Posted by Road Fan

As well, the portfolios of both Reynolds and Campagnolo had tubes with nominally thicker walls (1.0 mm) versus "normal" (0.6 mm in the case of Columbus) and thin walls (down to 0.4 mm for both Columbus and Reynolds). These were options available to the framebuilders of the day. The stiffness was the effective variable - want a stiffer frame, get a tube with a thicker wall, just basic engineering. Much more to it, though: how much thicker, butt v belly, butting profile for each tube, are head and seat tube angles affected, and what do we do beyond the main triangle? While Trek's catalogs on the 5xx, 6xx, and 7xx identify tubesets used in those series of frames, you didn't get an actual build sheet when you bought a 610 back in the day. So there is no confirmation of "what is my frame made of?" However, the docs on Vintage Trek seem to indicate that most 531 tubesets used by Trek had 10/7/10 DT profiles, rather than 7/.56/7. The 710 may have been an exception. My '84 610, at least in the Vintage Trek site seems also to be DT 10/7/10, and though I have ridden it off and on for years, it's not my favorite ride.

For the 720s, at least 1982, Trek claimed (again, inferring based on the catalog information) the 531 TT was 8/5/8, DT was 10/7/10, and ST was 9/5. For 531SL, TT was 7/5.6/7, DT 7/5.6/7, and ST was 7/5.6. My 1982 720 was claimed to be "Main Tubes Reynolds 531 Double-butted Manganese Molybdenum" and "Forks & Stays Reynolds 531" with Reynolds sstickers claiming fully double-butted tubes, fork, and stays, however they phrased it. At different times Reynolds claimed the butts/bellies profiles of their tubesets, and usually the "standard" one had a 9/5/9 DT rather than a 10/7/10. That's the only difference between the two spec sheets, so it is reasonable to assume that there is some stiffness difference between a 720 in 52 cm c-c versus, a Reynolds based bike build to the Reynolds spec sheet. There may have been more "framebuilder tricks" BITD to make a stiffer bike. So it's not unreasonable for the 720 to ride stiffer than some bikes, but also remember the extra-long chainstays ...

So I'm not sure it makes sense that the Trek 720 was intended to ride with the stability of what is now considered to be a serious touring machine, and can be reasonably compared to one. I haven't built mine yet, it still needs alignment and cold-setting, and I need to decide if it's getting repainted, 650b conversion, canti posts (82 was NOT made with canti posts), yadda yadda yadda. I expect it to be a good, comfortable, get on and go 40 miles bike. It'll be getting an old Campy 8 or 10 triple or compact group, so we'll see how it works out!