Quote:
Originally Posted by comptiger5000
My Jeep didn't really do much mpg wise (within measuring error) when I stepped up from 225/70R16 to 245/70R16 tires (yes, I corrected the speedo). It dropped me from about 1825 rpm at 60mph to about 1760 rpm at 60mph. It definitely didn't hurt though.
However, keep in mind, with a 360 in the Jeep, it's still very over-geared, and will climb 7% grades (with 2 people and a couple hundred pounds of crap in it) at 60 with the cruise set without a downshift.
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Wikipedia is wrong, the first number is the tire width and the second number is the height, expressed as a % of the width. So in the example you gave comptiger, your tires got 20 mm wider and 2*20*.7 taller. Wouldn't the wider tire cancel out some of the gains?
I planned on going from 225/60 (stock) to either 225/65 (3% increase) or 225/70 (6% increase). Width remains the same, but the height is increased.