Quote Originally Posted by Stol3n View Post
the 325 & 345 shouldn't affect mph unless one of the sidewalls are larger.
Just so you know the "series" or tire height changes as a tire get wider. A 345/30 is not the same as a 325/30. I believe the way it goes the 30 is a percentage of the width of the tire. So sidewall height is 30% of tread width. Or something like that. That may be wrong(percentages part) but the principle of how the two change together is accurate.