Bike speeds, or gears, work by changing the relationship between how fast you pedal and how fast your wheels turn, allowing you to maintain an efficient pedalling rhythm across different terrains.
Understanding Bike Gears
At its core, a bike's gear system acts as a converter. Your gears convert your input at the cranks into an output at the back wheel. This means the energy and speed at which you pedal are translated into rotational speed at your rear wheel, which propels you forward.
The key to how speeds work lies in the ratio created by the different-sized sprockets (gears) on the bike, typically located at the front (crankset) and rear (cassette).
How Gear Ratios Affect Speed
Changing gears alters this ratio:
-
Lower Gears (Easier Pedalling): When you select a low gear (usually a smaller gear at the front and a larger gear at the back), the ratio makes it easier to turn the pedals. For every rotation of the cranks, the rear wheel turns fewer times.
- Benefit: Requires less effort, ideal for starting from a stop or climbing hills.
- Trade-off: Results in slower overall speed for a given pedalling speed (cadence).
-
Higher Gears (Harder Pedalling): When you select a high gear (usually a larger gear at the front and a smaller gear at the back), the ratio makes it harder to turn the pedals. However, for every rotation of the cranks, the rear wheel turns more times.
- Benefit: Allows you to achieve higher speeds on flat ground or downhill.
- Trade-off: Requires more effort and leg strength.
As the reference states, Your cadence (how quickly you are pedalling) is converted into different speeds at your back wheel depending on whether you are in a high or low gear. This is precisely how you can pedal at a comfortable rate while adjusting your speed to suit the conditions.
When to Use Different Gears
Choosing the right gear helps you maintain an optimal cadence, usually between 70-90 revolutions per minute (RPM), preventing your legs from getting too tired or spinning too fast without gaining speed.
Here's a simple guide:
| Gear Type | Effort Per Pedal Stroke | Wheel Speed (for same cadence) | Best Use Case |
|---|---|---|---|
| Low | Less | Slower | Starting, Uphill Climbing |
| High | More | Faster | Flat Roads, Downhill Riding |
By shifting gears, you effectively change the leverage system of your bike, making it easier or harder to pedal, and consequently, slower or faster at the wheel for the same pedalling effort.
