I'm 5'-8.5" and the smallest bike I can ride is a 52cm. The seatpost is maxed out and the stem is a long 120mm extension, but it feels great!
I think 49cm size is still workable for someone 5'-6"...
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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)