I would like to change my tires to a "flatter" profile tire and would like to keep my final drive ratio the same. so the question is how do I figure out my final drive, and figure out my new final drive? e.x old tires 24x10x10 with an 11 tooth front and 30 tooth rear. I want to change to a 22x10x10 tire and keep the same ratio like i never changed the tires.

thanks

john

 

John-

To determine the ratio of countershaft rotation to vehicle displacement, use the following formula: (Tcs/Ts)*(PI*Dw)
Where: Tcs = number of teeth on countersprocket
Ts = number of teeth on sprocket
Dw = diameter of wheel

With your present setup, each rotation of the countershaft propels your ATV approximately 27.6 in. (11/30*3.14*24) This is the ratio that you want to maintain when you switch to the smaller tires. With the tires selected, there remains two other components that effect this ratio – the countersprocket and the sprocket. The following equation should help with your selection of sprocket sizes: (Tcs1/Ts1)*(PI*Dw1) = (Tcs2/Ts2)*(PI*Dw2) where the variables are as defined earlier but the “1” indicates the existing size and the “2” indicates the new size.

Solving the equation for Ts2: Ts2 = (Ts1*Tcs2*Dw2)/(Tcs1*Dw1) - Use this equation to determine the new sprocket size once the new countersprocket size has been chosen.

Solving the equation for Tcs2: Tcs2 = (Tcs1*Ts2*Dw1)/(Ts1*Dw2) - Use this equation to determine the new countersprocket size once the new sprocket size has been chosen.

Doing the math yields the following compatible ratios(Tcs:Ts): 11:25, 12:27, 13:30. I don’t know what sizes are available, but I suggest choosing a countersprocket with at least 12 teeth to limit chain stress. Hope this helps.

Greg McKinney