Gearing Ratios

Remember in high school, doing math you thought you'd never use? Well Gearing Ratios is one of those things!

In general:

A smaller front (countershaft) sprocket or larger rear sprocket will make your bike accellerate faster, but have a lower top speed. It will also make the chain slightly looser, and you will probably need to move the rear wheel back slightly to compensate. This creates a lower gearing ratio

A larger front sprocket or smaller rear sprocket will make your top speed faster, but your accelleration will be slower. You may need to move the rear wheel forward slightly. This creates a higher gearing ratio

As a general rule, changing one tooth on the front sprocket is roughly equal to changing the rear by four teeth!

Now for the ratios

Front Rear Ratio
13 X 40 3.08
13 X 41 3.15
13 X 42 3.23
13 X 43 3.31
13 X 44 3.38
13 X 45 3.46
13 X 46 3.54
13 X 47 3.62
13 X 48 3.69
13 X 49 3.77
13 X 50 3.85
13 X 51 3.92
13 X 52 4
13 X 53 4.08
13 X 54 4.15
13 X 55 4.23

 

Front Rear Ratio
14 X 40 2.86
14 X 41 2.93
14 X 42 3
14 X 43 3.07
14 X 44 3.14
14 X 45 3.21
14 X 46 3.29
14 X 47 3.36
14 X 48 3.43
14 X 49 3.5
14 X 50 3.57
14 X 51 3.64
14 X 52 3.71
14 X 53 3.79
14 X 54 3.86
14 X 55 3.93

 

Front Rear Ratio
15 X 40 2.67
15 X 41 2.73
15 X 42 2.8
15 X 43 2.87
15 X 44 2.93
15 X 45 3
15 X 46 3.07
15 X 47 3.13
15 X 48 3.2
15 X 49 3.27
15 X 50 3.33
15 X 51 3.4
15 X 52 3.47
15 X 53 3.53
15 X 54 3.6
15 X 55 3.67

 

Front Rear Ratio
16 X 40 2.5
16 X 41 2.56
16 X 42 2.63
16 X 43 2.69
16 X 44 2.75
16 X 45 2.81
16 X 46 2.88
16 X 47 2.94
16 X 48 3
16 X 49 3.06
16 X 50 3.13
16 X 51 3.19
16 X 52 3.25
16 X 53 3.31
16 X 54 3.38
16 X 55 3.44

Comments

hey i dont mean to sound thick but all this gear ration does not mean anything to me well i get the main part 16 X 55 but i dont get the 3.44 part sorry for pissing u off with this question

simon's picture

To turn the rear sprocket once, the counter shaft sprocket has to spin the number of times in the "Ratio" column.

So if the CS sprocket has to spin 3.5 times, thats lower geared than if it had to spin 2.5 times to turn the rear sprocket (and thus the wheel) once.

so what do u think would be best for my bike a yz125 i ride enduro most

simon's picture

You have to think about what sort of riding you do.

If you often find yourself lacking top end speed, you may need to go for a lower ratio.

If you find first gear is too tall, you may need a higher ratio.

If you find the bike lacking power, gearing it down can help. If its got too much power, and lacks traction, gearing it up can help.