For the Bicycle Federation of Wisconsin Never changed gears on my bicycle, and I do just fine, thank you. This is a stock phrase uttered by those who don't really understand bike gears. Learn how to use your bike and your body to their fullest. Shifting gears keeps the engine within the range.
Bicycles follow the same principle.
Except, on a bike, your body is the engine, and how fast you are pedaling determines the rpm. From 70 to 90 pedal rpm is ideal for bicycling. It should be maintained uphill, downhill, on flatland, against a head wind or with a tail wind. Pedal rpm translates into cadence, and the goal is to keep this constant. Everyone has a different cadence.