# Thread: Gearing on a MTB.

1. ## Gearing on a MTB.

This question always still puzzles me and even though I got some answers in the past I still want to know 100 percent.

Gearing on a MTB.

Let say I have a 45 tooth up front and a 15 tooth in rear. That is a 3:1 ratio. Is that as easy to get up to speed and maintain speed as if someone had a 30 tooth in front and a 10 tooth in rear?

2. ## Gearing on a MTB.

30:10 would be lighter. The number of crank revolutions would be the same but the power required would be slightly less because of lower weight. Probably only noticeable when climbing if at all.

3. So even though each revolution in the front is 45t and is easier to spin the tire in the rear with a 15tooth, you still think the power needed to get the same speed as fast between the 2 is the same?

4. ## Gearing on a MTB.

The ratio is 3:1. Disregarding weight, the effort would be the same.

A more realistic 3:1 gear on an MTB would be 36:12.

5. ## Gearing on a MTB.

Gearing is based on the front chainring size, rear sprocket size and wheel size. The same combination of chainring and sprocket when used on a 29" or 26” wheeled bike will result in a different gear ratio (in gear inches), the bigger wheels making it a higher gear.

You can use the Sheldon Brown gear calculator to compare different combinations. Use 700x50 or 700x56 for 29" MTB wheels.

http://sheldonbrown.com/gears/

Using larger chainrings and sprockets is supposed to have slightly less friction.

http://chasingwheels.blogspot.co.uk/...-smoother.html

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