Setting up mountain bike gears 

Gear mechanisms in mountain bikes are growing much more complex and the bicycles at present contain as many as 27 gearing ratios.  Any mountain bike will use a mixture of 3 various sized sprocket wheels in the front and 9 in the rear to produce gearing ratios.

The concept behind all these gears is to permit a rider to crank their pedals at a constant interval no matter what sort of incline the bicycle is situated on.  You could understand this better through picturing a bike with simply one gear, so that every time you rotate your pedals one turn, the back wheel would rotate one turn as well - a (1:1 gear ratio).

If your back wheel is exactly twenty-six inches across, then utilizing 1:1 gearing, one full rotation of the pedals would end in the wheel  81.6 inches of road.  If you are pedaling at about fifty RPM, this entails that the bicycle can cover over three hundred and forty feet per minute.  That's just 3.8 miles per hour, which is the same as walking speed which is adequate for climbing a steep hill, though bad for ground or traveling downward.

To go faster you'll require a different ratio, so to descend downhill at 25 MPH with a 50 revolutions per minute cadence at the pedals, you will require a ratio of 5.6:1.  A bike with lots of gears would provide you a large amount of increases in between a 1:1 gear ratio and a 6.5:1 gear ratio so that you could constantly pedal at 50 RPM, no matter the speed you're actually going. On a standard twenty-seven speed mountain bike, 6 of it's ratios are so close to each other that you cannot discern any variation between them.

With actual use, bikers tend to pick a front sprocket wheel suitable for the slope they are biking upon and stay with it, however the front sprocket may be tough to shift while under full load.  It's much simpler to change between gears on the rear therefore if you're going uphill, it's best to choose the tiniest sprocket wheel in the front then shift between the 9 speeds you have on the rear.  The more gears you possess on your back sprocket, the bigger advantage you'll possess.

Broadly speaking, gears are extremely critical for mountain bicycles as they dictate your overall velocity and if you didn't have gears you would not have the ability to build speed nor would you be able to pound the pedals.  The gears will roate your foot pedals and aid you in building up speed.  There's many variations of geartrains for sale for mountain bikes, all of which will help you build up a great deal of forward motion if you can utilize them in the correct manner.