why and how do gears on a bike work? Why does it give more / less resistance for going up and down hills?
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Gears (and pulleys) are literally a form of lever. A long lever makes it easier to move something at the cost of having to move the lever farther. Similarly, the “easier” gears of a bicycle reduce the effort of climbing a slope at the cost of having to rotate the pedals more times.
Do you remember when you learned about pulleys in school?
When you have one pulley it’s harder to pull than when you have four pulleys.
When you have the rope running around four pulleys you have to pull the rope much farther than when you had just one.
It doesn’t take a lot of effort to turn a small gear whereas it takes a lot of effort to turn a large gear.
If you connect a small gear to a large gear, it is easy to turn the small gear which (in turn) turns the large gear, but only very slowly.
In reverse, you can put a lot of effort to turn a large gear connected to a small one, which then turns the small one very fast.
So by choosing the appropriate *gear ratio* (the comparative sizes of the gears) you can trade effort for speed and vice versa.
it changes how many far the wheel turn (how far you move) for each turn of the pedals
it is easier to turn the pedals in a low gear but slower, just like it easier but slower to move ten 10kg weigths than it is to move one 100kg weight
It’s difficult to enjoy biking when your feet can barely move the pedals or when the pedals spin so fast your feet cannot keep up. Generally, a cadence of 75 to 90 pedal rotations per minute is comfortable for most bikers. Adjusting the gearing of your bike allows you to keep this pedaling cadence when traveling at any speed.
Gears work as ratios. If you’ve ever ridden like a 21 speed bike, they generally have 7 gears on one side and 3 gears on the other (which multiply to give 21). The 3 front gears sit in line with the pedals and are called chainrings. The 7 rear gears are in line with the axle of the rear wheel and are called the cassette collectively and cogs individually. The large and small chainrings are intended for extreme circumstances: large hills or fast road riding. Don’t use the small chainring with the smallest cogs in the cassette or the large chainring with the largest cogs. This places the chain at too much of an angle, increasing wear on your bike and raising the risk of your chain jumping off the gears while riding.
Imagine three chainrings: 28/38/48 and a 7 speed sprocket set 12/13/15/17/20/24/28 (this is number of teeth on each gear). You can now setup pairs between the 2 sets of numbers to get ratios. [(28,12),(28,13),(28,15)…..(38,12),(38,13),(38,15)……(48,12),(48,13),(48,15)….]. Now the informative part is the ratios. You get[{(2.33:1),(2.17:1),(1.87:1),(1.65:1),(1.40:1),(1.17:1),(1:1)},{(3.17:1),(2.92:1),(2.53:1),(2.24:1),(1.90:1),(1.58:1),(1.36:1)},{(4:1),(3.69:1),(3.20:1),(2.82:1),(2.40:1),(2:1),(1.71:1)}]. The curly brackets denote each set of 7. You’ll see some pretty close overlap in several of the ratio. This is because you don’t get 21 indepent gears, you get 7 high, 7 medium, and 7 low. Or if you look at it independently 5 high, 7 medium, and 5 low. The overlap helps cut down on complicated gear shifting of both sets for mechanical wear and tear reasons.
So, if you are in steep ascending landscape, you select your low gear range (smallest chainring)
If you are in steep or moderate descending landscape, you select your high gear range (biggest chainring)
For most other situations, moderate ascending and descending, you select your mid gear range (middle chainring)
If on tarmac, you possibly alternate between mid and high ranges.
By having three gear ranges which overlap significantly, you will find that you can minimise the changes of front chainring selection, making your gear transitions smoother.
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