I had a no frills single speed sting ray, I rode it bmx style at an empty tract of land that had a network of singletrack on it, including berms, drops, drop-ins, etc. No racing, just fun riding. Didn't take good care of that bike but it held up well. That land is a shopping center now.
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1989 Schwinn Paramount OS
1980 Mclean/Silk Hope Sport Touring
1983 Bianchi pista
1976 Fuji Feather track
1979 raleigh track
"I've consulted my sources and I'm pretty sure your derailleur does not exist"