I didn't really pay attention to the rpm with my old tires. All I know is my OD always starts at 37mph.
Waiiiit... I thought you just said :
Originally Posted by Compaq888
My rpm stays the same at any speed, but the mpg just go up. Doesn't matter what tire I'm using.
It seems that you either paid attention to your RPM or you didn't. Both of your statements can't be correct.
I explained to you in the IM the difference between them.
I'll explain for the rest here too.
My OD went on at the same speed with both tires, but the 3 other gears are way different.
Next taller tire is actually different. I went to the track a couple of times with my 195/65/15 tires and I got consistent 2.4xx 60'. With my kumho's that are 205/60/15 my 60' actually got worse because they are shorter. My 60' was 2.5xx-2.6xx with the 205/60/15. The kumho's are wider so I should have more traction and some of you are going to say that the other tires were of better compound and hooked up better and that is where you're wrong. My other tires would barely hook up in the rain for regular street driving and I almost wrecked 3 times in one month because of them. I even bought the kumho's because I eventually did wreck because of them. Now the kumho's have great traction, I can make turns at higher speeds and they have great wet traction. I actually have to go WOT just to spin my tires in wet traction.
So the conclusion is having a bigger tire makes a difference at the track and it should improve your fuel economy because it spins less per mile than the smaller tire.