70mph?

[CATCRACKER]

with 3. 73 and 315's i need to know where true 70mph is. what is the rpm and mph guage reading at a true 70mph?

 

[Fireman]

Go out and measure the circumference of your tires and do the math.



Fireman

 

[RankRam]

I use a GPS for my speed quandries.

 

[Mathew Clausen]

According to BFG and Michelin websites here are the following for revs/mile for stock vs 315/70 AT's



Stock - LTX a/s 265/70-17 = 657 revs/mile

BFG AT 315/70-17 = 601 revs/mile



Assuming your speedo is correct with the stock tires (mine is nearly perfect) you are going to be 657/601 = 1. 09 times faster than indicated on the speedo (9% faster). If you want to go 70, your speedo should read 70/1. 09 = 64 mph.



Best and easiest way to double check is use a gps.



Mathew

 

[CATCRACKER]

thanks matt!

 

[DBVZ]

This is a useful site for some of these questions:



http://www.f-body.org/gears/