the campy pista is ~33.7mm, so I assume the gran sport is also. My chris king is 33 mm, as well as the tange. campy NR is 39mm.
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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"