Posted by Aaron A. Arnold on Tuesday, December 12, 2000 at 17:01:00:
In Reply to: engine RPM posted by chewie on Tuesday, December 12, 2000 at 04:05:04:
mutliply tire diameter (ex. 38") by pi (3.14)
= 119.32" divide by 12" = 9.94' is the distance of one full revolution of your 38" tire. Divide 5280' by 9.94', this is how many revolutions of your tire in one mile = 531.187 multiply this by your gear ratio (ex. 4.88) = 2,592.19 which is your rpms at 60 mph.