Gearing Ratios

By simon, 10 April, 2005

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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

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.

hey simon

Ratio

so

It depends