Gear ratios- as I understand them.
There are two wheels connected by a chain.
You apply power or energy to wheel one. It makes the chain to move. That in turns makes the second wheel to rotate. Your second wheel is connected to the rear wheel of your bike. So your rear wheel rotate and the bike move.
Now by changing the sizes of these wheels, you can make your rear wheel to rotate faster or slower.
Imagine your front wheel is the same size as rear wheel. You rotate front wheel once and rear wheel rotate once.
Rear wheel is half the size of the front wheel. So you rotate front wheel once and rear wheel moves around twice.
Size of the wheels are given by the number of tooth it has.
You can now write that in a simple formula like this.
Front divided by rear equals to gear ratio.
Multiply that by the circumference of the wheel. That is how far wheel will go.
My front wheel has 3 rings. 50-39-30
Rear has 10 rings, smallest cog 12 and largest cog 30.
That gives you 30 possible combinations or 30 gears.
Now try to work out gear ratios for each one of those possibilities.
50/30 going up to 50/12 for front ring.
39/30 to 39/12
30/12 to 30/30.
Because of frictions, you can not use the extremes, large with large 50/30 or smallest with small 34/12.
Now if you did the maths you will see that you can achieve the same ratio by using the different combinations. So in reality you do not have 30 gears to use.
Now that you understand the basic maths, next time you go riding, you can use different combinations for different purposes more effectively.
If you are still confused, feel free to ask.
