are 30's or 31's on stock suspension going to kill my mpg?

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May 31, 2011 | 09:25 PM

#16

98cherokeeguy

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Joined: May 2011

Posts: 113

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From: jacks

Year: 98

Model: Cherokee

Engine: 4.0

That what I'm looking at doing here soon

May 31, 2011 | 09:36 PM

#17

1996XJSport

CF Veteran

Joined: Sep 2010

Posts: 1,992

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From: West Bloomfield,MI

Year: 1996

Model: Cherokee

Engine: 4.0L, CAI, Edelbrock Breather, Optima Yellowtop

Quote:

Originally Posted by Metmknice

30s should be alright. 31's I wold recommend finding a 4cyl xj with 4.10s and swap axles.

Depends on if the axles are Dana 35s or something, if they are.... don't do it. Just buy a regear kit.

May 31, 2011 | 10:42 PM

#18

Metmknice

CF Veteran

Joined: Oct 2008

Posts: 2,127

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From: Hell, CA

Year: 1989

Model: Cherokee

Engine: 4.0L I6

Quote:

Originally Posted by 1996XJSport

Depends on if the axles are Dana 35s or something, if they are.... don't do it. Just buy a regear kit.

Even so.. if they can be had cheap enough, keep the front D30, and sell the D35

May 31, 2011 | 11:20 PM

#19

dogger15

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Joined: Apr 2010

Posts: 4,339

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Model: Cherokee

Quote:

Originally Posted by Biceps McRipped

215 refers to the width of a tire in millimeters, not height. The next number, probably 70 or 75, determines the height. Second number IS NOT the height. Next number is rim size. You're correct on the 30 inch tall tire. Metric tire sizing is annoying.

My jeep is lifted 3 inches with 31 x 10.5 tires and I lost 2-3 mpg from stock. I was riding on 225/75 tires. Both 15" rims.

Width is the key to your mpg. A wider tire is going to create more resistance because of the amount of contact with the road, meaning less mpg. I'm not saying a taller tire won't hurt your mpg, just that a wider tire will hurt it more.

A 215/75/15 is about 27.5/8.5/15 give or take a little bit each tire brand is different if that helps you out. Majority of people know that the 215 isn't tire height. Got lazy during my post. I worked in a tire shop for a while

If you have a tac and go with bigger tires keep and eye on your rpm. I'm getting about the same mpg from when I had the 215/75/15 to the 30/9.5/15. Also yes it does help that I have a 5 speed

As for tire width its not going to make that much of a difference for you to notice.

Last edited by dogger15; May 31, 2011 at 11:39 PM.