Why does running one size bigger tires increase fuel economy?

[GasSavers_worthywads]

Originally Posted by SVOboy

Prolly a wash I'd say, or an expensive experiment it'd be hard to ever know the results of. What's the bolt pattern on the element?

Is 5x114.3 the bolt pattern?

I'm at 20,000 miles and will be needing new within the next 10,000 it looks. I won't be deciding until the oem Wranglers are toast, but they are wearing fast.

[SVOboy]

Yep, search from some lightweight rims for that stuff, , that's the same bolt pattern as the ITR so you can get some nice stuff,

[GasSavers_worthywads]

Originally Posted by SVOboy

Yep, search from some lightweight rims for that stuff, , that's the same bolt pattern as the ITR so you can get some nice stuff,

ITR?

Is there a ROI on lightweight rims?

[SVOboy]

ITR = Integra Type R
ROI = ?

[Matt Timion]

Originally Posted by SVOboy

ITR = Integra Type R
ROI = ?

ROI = Return on Investment.

lighweight rims will help as it reduces rotational mass, but the ROI is unknown. It's probably one of the "hard core" modifications for extreme enthusiasts.

[Compaq888]

Originally Posted by MetroMPG

remember though, the mileage benefit from a taller tire comes from reduced engine/transmission rpm. so if your rpm doesn't drop with a larger diameter tire...

I didn't really pay attention to the rpm with my old tires. All I know is my OD always starts at 37mph.

[Matt Timion]

Originally Posted by Compaq888

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.

[Compaq888]

Originally Posted by Matt Timion

Waiiiit... I thought you just said :

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.

[krousdb]

Originally Posted by Matt Timion

lighweight rims will help as it reduces rotational mass, but the ROI is unknown. It's probably one of the "hard core" modifications for extreme enthusiasts.

I don't understand the issue with rotational mass and FE. Sure, you invest more energy to accelerate, but you get it back while coasting. ;-)

[Matt Timion]

Originally Posted by krousdb

I don't understand the issue with rotational mass and FE. Sure, you invest more energy to accelerate, but you get it back while coasting. ;-)

I think the FE gain with lightweight rims is all in city driving. It requires less energy (ie, fuel) to spin the tires. For stop and go traffic, that would be a major bonus.

I'm also sure that it takes a slightly less amount of energy to maintain a cruising speed with lightweight rims.