two questions:

1. does anyone have available to them the formulas for figuring out gear ratios? im looking to put an ls 5th in my si tranny... and want to know how to calculate ratios. my auto math book is at home rite now.

2. once i know ratios, how do i estimate rpms at certain speeds? I prefer not to interpolate since i know si rpm, and will now (hopefully) know ls ratios..

anyone know the formulas? thx!

 

(rpm * tire diameter)/(FD * gear's ratio * 336)

this sorta helps and so does this for the most part
http://tiiite.b16a.com/Bgears.htm

 

thx Lip.

hmm, the formula seems to give you the theoretical max speed you can go using the variables you input...

im assuming the 336 is a conversion factor to get you from inches-rev/minute to miles/hour.

so, using that, and mating a b16 tranny with LS 5th, I can theoretically go 174.3 miles/hr on my 15" rubbers... nice to know.

Here is another site that goes one step further.. now all i have to do is find out the formulas it uses.
http://www.autocrossing.com/cgibin/gearcalc.cgi