If I lived in your climate, I would cross country ski.
Besides having fun and hanging around fellow vintage bike nerds, I don’t really have any goals for the Eroica ride other than finishing in one piece.I view it as a series of 20-ish mile rides between rest stops, so I focus any training on riding as often as I can weather permitting and getting as much climbing in as possible. I search out the 15+% dirt/gravel climbs and make sure I get some reps on those with my Eroica bike.
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N = '96 Colnago C40, '04 Wilier Alpe D'Huez, '10 Colnago EPS, '85 Merckx Pro, '89 Merckx Century, '86 Tommasini Professional, '04 Teschner Aero FX Pro, '05 Alan Carbon Cross, '86 De Rosa Professional, '82 Colnago Super, '95 Gios Compact Pro, '95 Carrera Zeus, '84 Basso Gap, ‘89 Cinelli Supercorsa, ‘83 Bianchi Specialissima, ‘VO Randonneur, Ritchey Breakaway Steel, '84 Paletti Super Prestige, Heron Randonneur