| It's not uncommon for modern mountain bikes to | | | | to another. |
| have as many as 27 gear ratios, or "speeds." Not | | | | The size of the sprocket affects the gear ratio, and |
| that long ago, a 10-speed bike seemed like it had a | | | | therefore the amount of force you need to exert to |
| lot of options. Are these 27 speed bikes just a | | | | maintain a certain speed. Smaller sprockets are easier |
| marketing ploy to make it sound like you're getting | | | | for you to turn, but they have to go through more |
| more? Not necessarily, let's look at why this is. | | | | revolutions to cover the same distance. |
| If a bike didn't have multiple sprockets and derailleurs, | | | | Balancing the gear ratio against the force you have |
| the chain would encircle one rear sprocket, resulting in | | | | to exert allows you to make it easier to pedal uphill |
| a single 1:1 ratio. So the rear wheel would spin at the | | | | while maintaining a reasonable speed. On level ground, |
| same speed that you can pedal. | | | | you can switch to a larger sprocket, letting you go |
| If we look at the math, for a 26" wheel it would | | | | faster with a moderate amount of force. |
| have to travel about 82 inches for one full revolution. | | | | While these gearing systems make it easier to |
| If you pedaled at 50 RPM, you would move roughly | | | | manage the force you need to exert, single speed |
| 340 feet per minute. In other words, less than 4 | | | | mountain bikes are still popular with many people. |
| miles per hour, which is not very fast. | | | | While they only provide one gear ratio, the biggest |
| Increasing the number of gears lets you go faster by | | | | advantages people like are lower weight and |
| multiplying the revolutions of the pedals when they're | | | | simplicity. |
| transferred to the wheels. More gear ratios let you | | | | The gear ratio can be adjusted according to the |
| manage the amount of effort you need to exert | | | | needs of the rider, but once it is set, it stays at the |
| over different slopes and different types of surfaces. | | | | same ratio. But because of the weight savings and |
| The basic technology that makes this possible is | | | | especially the lack of maintenance on the shifting |
| called the derailleur. These are the small metal | | | | system, many people prefer this option. |
| mechanisms that shift the chain from one sprocket | | | | |