HELP!! Please With Gear Ratio

[s10king91]

I have figured out how to calculate the gear ratio from the clutch to the rear sprocket but i need to know how in the world i figure in my back tires maybe you guys can help get me where i wanna be
im looking for a 8.0-9.0 looking for off-road a torque converter is not a option as i am building this on a budget for a friend.

what i have right now is 18" back tires 72 tooth back sprocket #35 chain and i am thinking im going with a 10 tooth driver which puts me at a 7.2 gear ratio but how do i figure in the tires and is there any thing else i can change to get a higher final drive ?

Thanks For Reading And any Answers i get are very helpful.

 

[Doc Sprocket]

http://www.diygokarts.com/speed-calculator.html

 

[s10king91]

Thank You Life saver i searched all day today on this forum and i must have overlooked it 100x's i new it was on here but could not find it.
Thanks

 

[r97]

if you want off road power i would suggest a 10t #40 clutch to a 15, 17, or 20t sprocket on a jack-shaft then to a 10t on the jack shaft and then to a 60t on the axle, 15t would get a little more speed but hurt power, 17t would be the mid range with good power and good speed, 20t would give nice power and ok speed, remember the lower the ratio the more power and less speed the higher the ratio more speed but less power, i know you said its not an option but with a tc you could have far superior power to the 20t option and hit about 30 with correct gearing