Originally Posted by stardognine

If you look around closely, on the serial number pages, there's a link to the production totals, for each model & each year. It's a spreadsheet thingie, that someone made up from Trek's data, in their journal. I think I said that right, but when you find it, you'll see that I'm at least mostly right. 😉 BTW, I looked around there again yesterday, and there was an '86 Trek 520 Cirrus, with fairly long chainstays, but no 620 Cirrus. Don't sweat it, I'm sure it was an honest mistake. I know I've had to read through that site several times, it's fairly confusing. 🤔
And hey, read that '86 brochure again, especially the introduction paragraphs, for each category (racing, touring, etc.) . It clearly states that all the steel frames assembled with the new robots, were brazed with silver rods. Obviously, not the aluminum & carbon frames, lol, but the steel ones, which were obviously made in much smaller numbers. 🙂

Originally Posted by stardognine

Yep, I was mistaken yet again, lol. �� I didn't search for the 620 Cirrus again yet, but you're absolutely right about lots more frames being built in '84, for the '85 model year. All the clues are there, but it still gets tricky, for dummies like me. �� So, maybe I can upgrade model years after all. �� ��

Originally Posted by The Golden Boy

I think you're making a much much bigger deal out of it than it is.

First, the wheel size is independent of the distance between dropouts.

Second- the 80s Treks are spaced at 128 so they can go to 126 or 130 with no mechanical spreading other than your fingers and minimal (I mean minimal) effort.

Third- think of all the 120 to 126 and 126 to 130 conversions you've seen here (and the millions more throughout the world in the past 30+ years)- and think of how many mentions you've read of a chainstay failing from spreading a rear end from 128 to 130.

You're tying your shoes together by not considering a different wheel set. If you're OK with the Helicomatic- take care of it- there's (a few) people that still have them running. I guess it's just suggested to maintain them a little more often.

Again- there's no real problem in staying with 27" wheels- the bike was designed for them- and there's still quality tires around. I've used both the Pasela 1 1/4" and Sand Canyon 1 3/8" tires. I just took the 720 to a 10 speed 130 rear end and 700c wheels. And I'm SO glad I did.

If you're curious about it- try it- you can always go back Just don't spread the thing to 135.

Good Luck!!!