Rear gear question

[DJW32]

Hello,
I tried searching for a calculator that would show me the difference between tire diameter and overall gear ratio...

I know that 20" wheels changes the overall gear, but by how much? Does anyone know of this calculator?

Thanks, David

[osdmike]

http://www.5speedtransmissions.com/calculators.html


:twothumbs

"Osdmike"

[GetMore]

Wheel size doesn't change anything, it's the tires.
To figure out approximately how tall a tire is take the tread width, multiply it by double the aspect ratio, divide by 25.4, and then add rim diameter.
For example, 195/75/14 will be 25.5" tall. 195 is the width. The aspect ratio, 75 is actually a percentage, so it's really .75, when multiplied by 2 it is 1.5, and the last number, 14 is your wheel diameter.
Now, let's say you wanted to upsize and use 17" wheels. A 275/40/17 is a good match, at 25.6" tall.