May is bike month! If you're a newbie to cycling, you may not know what that means... basically, the month of May is set aside to encourage people to bicycle to work, run errands, and for recreation. Not only is it good exercise, but it also helps save the environment! :) Anyway, although I've had my bicycle for over 10 years, I really don't know "how" to ride. While I was searching online for when to shift gears/speeds on my bike, I found this
article which was really helpful for me. Maybe it will help answer your question about "why does a bicycle need 21 speeds anyway?"