for those with 18's
 

Im currently running a 235/40/18 's my question is this how high or low should my rpm's be cruising at 75mph...... im gonna throw some variable's in it.First i keep a/t select button in power mode while on the highway and overdrive on secondly my flexpipe is about shot.im turning about 2900 to 3000 rpm's at 75mph is this wrong or right or to high to low

If you look in the tire and wheel section, there is a tire calculator.

You should be able to figure out what percentage your tires are off. Stock size is 205/65/15, just put that in and the size you have and it will give you a percentage.

Then, you can figure out appx where you should be with regards to your rpm.

kool 1010 tires size my speedo is to fast thats weird:scratch:

i got 245/40 r18

When I did the reasearch those where about dead on. maybe 1% off.

i thought my 235 was wide the percentage for mine was .0343

yeah... the tire actually is stretched :)