Hi all! Can someone explain to me why it is that you can "add" to the rear sprocket, or "take from" the front sprocket to get the same effect?

Thanks,

Jason

 

It's a simple math equation to determine the final drive ratio for gearing

Take the number of rear sprocket teeth and divide that by the number of teeth on the countersprocket and you get the ratio.

I.E. 13/39 13 teeth on the countersprocket 39 teeth on the rear

39 divided by 13 equals: 3.00 ratio

You can get to any ratio by using different number of teeth on each sprocket. Typically a rule of thumb, is that for every 3 teeth change (+ or -) on the rear equals one tooth change on the countersprocket.

So if we do the math we see that:

13/39 = 3.00
or
14/41 = 2.92

Nearly the same ratio, or:

14/39 = 2.78

13/36 = 2.76

What I'm trying to show is the change of teeth on each and how it effects the final ratio. The "rule of three" mentioned.

I personally prefer not to go under a 13 tooth front and will change the rear to get a higher ratio as needed. Whereas for lower ratios I'll change to a larger countersprocket to get the ratio I desire.

 

it's closer to 2.5 teeth on rear = 1 tooth on fron(countershaft)