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35s? is the hit to mpg from the extra weight or the extra width?

Ratbert

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Just be assured nothing you do that increases the off-road capabilities of your Jeep helps fuel economy. The possible exception could be a full underbelly skid system, if its very light.
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roaniecowpony

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Ratbert

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A wider tire doesn't impact the contact patch, which is one reason a wider tire isn't (usually) better off road. A taller tire increases contact patch.
Are you positive about that? I used Tire Rack's +1 data to find two tires with similar diameters but one being wider.

A: 205/55R16 - 24.9" tall (narrower)
B: 215/45R17 - 24.7" tall (slightly shorter)

I took those details and entered them into this calculator where one of the results is contact patch area: https://bndtechsource.wixsite.com/home/tire-data-calculator

The results were that the slightly shorter, but wider tire had a bigger contact patch.

I obviously could have entered something wrong, or the calculator is off, but it looks like width has a positive impact on contact patch area.
 

2nd 392

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Essentially regearing to ~3.90, adding weight- rotational mass and rolling resistance increases the energy (fuel) required to get moving. Expectations?
 

mwilk012

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Are you positive about that? I used Tire Rack's +1 data to find two tires with similar diameters but one being wider.

A: 205/55R16 - 24.9" tall (narrower)
B: 215/45R17 - 24.7" tall (slightly shorter)

I took those details and entered them into this calculator where one of the results is contact patch area: https://bndtechsource.wixsite.com/home/tire-data-calculator

The results were that the slightly shorter, but wider tire had a bigger contact patch.

I obviously could have entered something wrong, or the calculator is off, but it looks like width has a positive impact on contact patch area.
It obviously does. From the article he linked even,

“ That size is based on a tire's overall diameter, inflation pressure, and the weight acting on it. Installing fatter tires widens the patch, but it also shortens it front-to-back.”

The assumption, a bad one, is that inflation pressure would remain the same. It doesn’t.
 

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Ratbert

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It obviously does. From the article he linked even,

“ That size is based on a tire's overall diameter, inflation pressure, and the weight acting on it. Installing fatter tires widens the patch, but it also shortens it front-to-back.”

The assumption, a bad one, is that inflation pressure would remain the same. It doesn’t.
I'm not sure why you quoted that. It says nothing about an overall increase or decrease of the area (e.g. square inches) of the contract patch.
 

mwilk012

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I'm not sure why you quoted that. It says nothing about an overall increase or decrease of the area (e.g. square inches) of the contract patch.
Feel free to read the article.
 

Ratbert

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Feel free to read the article.
I did, but I didn't blindly believe it. Instead I did my own research using an independent calculator.

The lines you quoted did not say that one had a more significant impact than the other. That's why I questioned why you quoted them.
 

AcesandEights

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You changed the wheel size, so you changed an important ingredient in the recipe.
 

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Went from the stock 285/70R17 BFG KO2s to 315/70R17 Goodyear Territory MTs. Per online info, the Goodyears only weigh 1 more lb per tire than the BFGS, 52 lbs vs 51 lbs.

I have an otherwise stock 392 with 3.73 gears and my average MPG before and after is virtually unchanged at a whopping 13.5 mpg...just my 2 cents.
 

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mwilk012

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I did, but I didn't blindly believe it. Instead I did my own research using an independent calculator.

The lines you quoted did not say that one had a more significant impact than the other. That's why I questioned why you quoted them.
I’m not sure what you’re trying to get at here.

It’s plainly obvious that wider tired of the same height have a larger contact patch, especially at lower PSI.
 

Ratbert

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You changed the wheel size, so you changed an important ingredient in the recipe.
From the article you linked:

"If other vehicular factors remain constant, increasing a tire's overall circumference is the only way to enlarge the contact patch."

Are you now saying that the article was wrong and changing wheel size impacts contact patch area too?
 

Ratbert

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I’m not sure what you’re trying to get at here.

It’s plainly obvious that wider tired of the same height have a larger contact patch, especially at lower PSI.
Some people here are saying that tire width doesn't impact contact patch size.
 

mwilk012

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From the article you linked:

"If other vehicular factors remain constant, increasing a tire's overall circumference is the only way to enlarge the contact patch."

Are you now saying that the article was wrong and changing wheel size impacts contact patch area too?
I didn’t link anything. I think that article is ridiculous. Makes way too many assumptions.
 
 



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