Final Drive Ratios

The final drive ratio of your bike is determined by taking the rear sprocket tooth count and dividing that number by the front sprocket tooth count.  For example if you have a 45 tooth rear sprocket and a 15 tooth front you would take 45/15=3.0  In this example your final drive ratio is 3.0.  The higher the number the more bottom end you'll have, but there is a poing where you will also start to lose your top end.  Here is a chart to show you all the final drive ratio's for the most common motorcycle gearing.

Front Sprocket
Tooth Count
  Rear Sprocket
Tooth Count
   Sprocket Ratio  
 
14   40   2.857  
14   41   2.929  
14   42   3.0  
14   43   3.071  
14   44   3.143  
14   45   3.214  
14   46   3.286  
14   47   3.357  
14   48   3.429  
14   49   3.500  
14   50   3.571  
14   51   3.643  
14   52   3.714  
 
15   40   2.667  
 
15   41   2.733  
15   42   2.8  
15   43   2.867  
15   44   2.933  
15   45   3.0  
15   46   3.067  
15   47   3.133  
15   48   3.2  
15   49   3.267  
15   50   3.333  
15   51   3.4  
15   52   3.467  
16   40   2.5  
16   41   2.563  
16   42   2.625  
16   43   2.688  
16   44   2.750  
16   45   2.813  
16   46   2.875  
16   47   2.938  
16   48   3.0  
16   49   3.063  
16   50   3.125  
16   51   3.188  
16   52   3.250  
17   40   2.353  
17   41   2.412  
17   42   2.471  
17   43   2.529  
17   44   2.588  
17   45   2.647  
17   46   2.708  
17   47   2.765  
17   48   2.824  
17   49   2.882  
17   50   2.941  
17   51   3.0  
17   52   3.059  
18   40   2.222  
18   41   2.278  
18   42   2.333  
18   43   2.389  
18   44   2.444  
18   45   2.5  
18   46   2.556  
18   47   2.611  
18   48   2.667  
18   49   2.722  
18   50   2.778  
18   51   2.833  
18   52   2.889