
')+Sep 11 2015, 11:42 AM-->
QUOTE(Rev (

') @ Sep 11 2015, 11:42 AM)
What's the gears for? Does it means 21 speed can climb hills better than 6 speed? Sorry.. never have bike with gears lol.
Do you understand the workings of a chain block? You know, when the car mechanic is taking out the engine from the car, they hang it on a chain mechanism. With light effort you can raise the heavy engine and lower it down as well. Same principle as the bicycle gearings.
If one turn from the front turns one turn at the back, that's 1 : 1 ratio. Usually the normal bike is 1 : 4 , meaning one turn of the pedal is 4 turns of the wheels behind. This is easy on a flat road.
What happens if you hit a slope and you can't seem to turn the pedals? That's where the gears comes in. We lower the gear, that is one turn from the pedal, turns only half the normal at the wheel. This makes pedalling easier but shorter distance. And if you go higher slopes, you lower your gear even more, making it one turn of the pedal and only one turn at the rear, making ratio 1 : 1 and this makes it even easier to pedal up the slope. So to summarize, the lesser the rear turns at one revolution of the pedals or cranks, we call it, the lower the gear and the easier it is to pedal. BUT if you use this setting on a flat road, the effort is so light that you will be free wheeling like a dog swimming.
For a road bike, the lowest gear is 1 : 1.39 ratio but in some instances, different cassette it goes to 1 : 1.3. This is the standard road bike crank lah!

There's another type called compact crank which is smaller which makes the ratio go a little bit more lower.
For a mountain bike, the lowest gear is 1 : 0.6 and now with the latest 11 speed from the Shimano XT and XTR it goes even further down to 1 : 0.55. That's how low the mountain bike can go. The front crank's chainring is smaller than the rear.
Hope I answered it in the simplest way.