Really surprised me when the crown race on my Gitane TdF turned out to be 27mm when I changed out the Stronglight B10 headset on the bike to an all aluminum A9, about a month ago..... which leads me to think that the 27mm crown race spec can occur on BSC threaded headsets too...
I had to switch crown races with another A9 headset I had in my stash to make things work out on the Gitane....
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72 Line Seeker
83 Davidson Signature
84 Peugeot PSV
84 Peugeot PY10FC
84 Gitane Tour de France.
85 Vitus Plus Carbone 7
86 ALAN Record Carbonio
86 Medici Aerodynamic (Project)
88 Pinarello Montello
89 Bottecchia Professional Chorus SL
95 Trek 5500 OCLV (Project)