Understanding High Gears on Bikes

[dEdt]

Why do bikes have higher gears? At a higher gear, I'm still pedaling with the same force, but at a lower speed, so my power output is lower. What's the advantage of higher gears?

 

[rcgldr]

In a higher gear, you would be pedaling with more force (more torque). The advantage of a higher gear is it keeps the rate of rotation near what is optimal for a rider at higher speeds. Wiki article:

http://en.wikipedia.org/wiki/Bicycle_gearing

 

[sophiecentaur]

Gears allow you to go at a range of wheel speeds whilst your legs are going at the same (comfortable) rate. You can only deliver power at a given maximum rate. Power is speed times force. So you can deliver, to the wheels, a high force at low speed (uphill) and a smaller force at high speed (going downhill) whilst your legs are working at the same rate.