Originally Posted by
sd5782
Thanks all. Kind of what I was thinking. Fun to learn stuff, but that opens up other cans of worms. Sometimes ignorance is bliss. Actually bike was up in stand with wheel and RD off. String around headtube to rear dropouts. Just a slight variance to one side. Spacer added which brought that side out which should have kept the centerline of the wheel the same as it was. Not real precise, but was reassuring to see it looking as it should. Now to set up the slightly less vintage RD to handle the 28 tooth freewheel. Still will be 5 speed vintage, but hopefully better shifting than the campy Gran Sport. Vintage is nice, and I have read posts of others having luck with the Gran Sport, but I haven’t.
...Gran Sport was a wonderful advance in 1951, with its parallelogram design. There are way better derailleur designs available in the used parts market right now that work way better. If they're available to you, just about any Suntour derailleur from the 70's works better. Even the lesser ones.
You can do a double check on where your wheel is running in the rear triangle relative to center plane by simply running a long straightedge along the head tube/seat tube line on one side or the other. See where it lands on the rim (works better with tyre off). Then do it on the other side. Compare results.
You can even eyeball it (roughly) with the wheel in the frame, and the bike in a stand turned upside down. You want your rear wheel/tyre to look like it's centered relative to the seat tube, when viewed with one eye open, square on and centered to the bike. That's how I usually set the adjuster screws in the dropouts, when a bike has them.