RE: engine/speed calculations

["Michael Gendimenico, SC9-32, 765-4903" <GENDIMEN@T12SYS.intel.com>]

>               final gear ratio
>     mph x  -----------------------    / (.0113636) = rpm
>               drive tire dia. in feet
>
>          For example, running a 3.91 rear end ratio and a
>     tire with a ***5.68' diameter*** (185/60HR-13), at 6000 rpm;
 
They must be BIG tires, 5.68 feet?????  Do you know what the tire diameter is
for 175/70R13?  Then I could figure out what ratio my rear is without looking.

Mike G.