speedo is out...mph to rpm calculations

[Marcus Tooze <tooze@vinny.cecer.army.mil>]

My speedo cable broke (again)...I did some quick calcs. and want to  see
if they figure w/ you guys. As I've only had the car a week, I hadn't
payed much attention to what rpm = what speed in 4th...

rear end is 3.27:1, 4th gear is 1:1, tires are 155/70/13

Tire circumference is ABOUT 70 inches... 0.0011 miles.

For 3000 rpm rear wheel turns 917 times ...

which equals 1.01 miles (~1 mile) 

so 3000rpm is about 60 miles an hour and 3500rpm is about 70????

Marcus 'my math went up the spout when i left high school' Tooze