So I am a bit of a noob. Im will go ahead a apologize for this.

I have a 1980s Schwinn, not 100% sure on exact age. The original wheels are beyond repair. They got me around for a few months, So now I figured I would convert to 700c. I have searched around and Some people say when changing to a modern rear cassette older derailers and such wont work. Is this true. If I run a 8 speed cassette will it work with my original components.

Thanks for the help.

There are vintage rear derailleurs that will work with 8 speed cassettes. I have a SunTour ARX on the rear of a Trek 760 with a 9 speed cassette (and it can handle 8 of them) .

Dura Ace 7400 works with up to 27 teeth? Whatever it is, I think I'm running one tooth below that on an eight speed cassette. Works great!

A lot of the older derailleurs, like Suntour Vx/Cyclone, were designed to work with either an integrated derailleur hanger or with a "claw", which puts the derailleur a lot further out than an integrated hanger. So they needed some excess movement range to accommodate these mounting options. Many of these were well into the 126mm rear spacing era, only 4 mm narrower than this. I just measured the width of the "claw" on one bike. It is about 4.5 mm. It is a Suntour Vx medium cage running across a 6 speed 14/30 freewheel now, but I've had a 7 speed 13/28 on the same derailleur/wheel/bike, which is spaced at 126mm. This tells me it would work on a bike w/an integrated derailleur hanger w/130 mm spacing unless I'm really missing something here.

Probably the reason people are telling you it won't work is because of the indexing issues, which is true, these are not designed to work with indexed shifters. But in friction mode, a lot of these old derailleurs will work fine.

Wouldn't the simplest thing be to just get some vintage 700c wheels and switch the original freewheel from the original wheels to the 700c set? That's how I converted my 80s Schwinn to 700c. No modern cassette, no component compatibility worries.

Thats what I have decided to do. Except I am gonna buy a new freewheel too. It had seen better days. I was thinking 700c for more options and more tire options. But I decided that I didnt really need all those options for my needs. Mainly riding around campus to class and some 10-15 mile rides a few days a week.