Originally Posted by
Caliper
Being a 1984, was this originally a frame made for 27x1 1/4" tires? If so, you can probably fit 700x35-37 tires in there due to the slightly smaller diameter rim of the 700c setup. Your limiting factor will likely be the chainstays. Also, find as wide a 700c rim as you can. The wider rim will plump up the tire and keep the rummer from flopping around with those wide tires for one, but also keep the braking surfaces further outboard, which helps with clearance for brake calipers. If your rim is super narrow (classic road rims) then the wide tire will end up in a "lightbulb" shape that may hit the caliper arms, as well as not being so stable for cornering. An internal rim width in the low 20's would be ideal, but those are getting hard to find for rim brakes it seems.
If you've got DT shifter brazeons on the frame and have brifters in your parts stash (or are willing to buy some old shifters from eBay) then you can get cable ends from several sources that will bolt on where the DT levers used to go. I've done this on four bikes and it works great. Modern or classic brifters and drivetrain and a classic frame play just fine together. I suppose the old stem shifters already come with a DT cable stop, so that would work fine as well.
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I did just this with my 1983 Trek 412. Upgraded the 27" rims to 700x19 to accommodate 10-sp cassette and 700x32 Challenge Gravel Grinders (cold-set frame to 130mm), used Origin8 bolt-on cable-stops to run STIs, and installed Dia-Compe BRS101 dual-pivot brakes to reach the slightly shorter rims. This was primarily a "parts bin" build, so I ran it as a 1x10, using a broken Front Der as a chain keeper. Interesting thing about the Challenge GGs is that they ballooned to 35.4mm when mounted. I had to inflate the tire after installing the wheel in order to clear the brake pads. Finished it off with a Soma Gary 2 bar. A really fun bike. The lightweight Ishiwata "022" frame was key. Came in at 23.6# as built, unlike the group of Trek 720/30/60 I repurposed as "gravel" bikes that were in the 27# range. Even my 2007 Bianchi Volpe weighed 25#
