Nobody talks about this one. It rewinds to when Onoda's upperclassmen were still figuring out who they were as riders, before they became the anchors of Sohoku's team, and it finds the exact moment each one decided that cycling mattered more than anything else. The movie earns its weight by showing you why these guys are worth following in the main series, not by explaining it. For anyone who finished the original run and wondered what made them tick, this answers it without feeling like homework.
Yowamushi Pedal: SPARE BIKE is a sports comedy-drama film that looks back at the earlier days of the third-year riders who anchor their cycling teams. It is split into two stories. In the first, Makishima Yuusuke signs up for the Sohoku bicycle racing club as a first-year, and his older teammates look down on him for his odd, dance-like riding style. The second shows how Toudou Jinpachi first came to road racing in his second year of middle school: a friend challenges him to a race, and at first he turns it down because he does not want to end up with helmet hair.