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Just had BF Goodrich Rugged Terrain tires, size 245/65 17 installed last night...........a little road noise, look amazing, BUT my miles per gallon of gas went from 12.1 to 9.8. YIKES!
 

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Measure the outside diameter of your new tires, and compare this to the original tires. If there is a noticeable difference, this can throw the computer off!
:eek:rangehat:
 

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Measure the outside diameter of your new tires, and compare this to the original tires. If there is a noticeable difference, this can throw the computer off!
:eek:rangehat:
245/65 17 is the stock tire size...........is it possible that it could still throw the computer off?
 

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Thats nuts, I went from stock to 255 75 Mud tires and my average only droped fro 15.9 to 14.6.
 

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245/65 17 is the stock tire size...........is it possible that it could still throw the computer off?
The size numbers 245/65 are a ratio, height to width. The 17" would be common, but different mfg's can have different starting points, hence different diameters. Tread depth would also be a consideration.
:eek:rangehat:
 

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I also dropped alot too.With stock tire size I was getting 12 mpg in the city,now with 265/70/17 general grabbers at2 ,i am getting a sickening 9.5.I understand I went from a 29.5" tire to a 32 inch tire.How much can that difference in tire size throw off the computer?I am getting my average mpg off the comp and have the hemi.my new tires are 50lbs a piece,this might not help.
 

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I also dropped alot too.With stock tire size I was getting 12 mpg in the city,now with 265/70/17 general grabbers at2 ,i am getting a sickening 9.5.I understand I went from a 29.5" tire to a 32 inch tire.How much can that difference in tire size throw off the computer?I am getting my average mpg off the comp and have the hemi.my new tires are 50lbs a piece,this might not help.

You spedo will be about 7.3 miles faster with the 31.7" tire. Your revolutions per mile will be about 46 greater. You bet this will throw off the computer!
 

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Discussion Starter #9
The stock Goodyear Forteras were the same size/measurements as my new BFG Rugged Terrains. Average MPG is down to 8.5 with the city driving in Washington, DC. It's a good thing my office is only 2 miles away from my condo!
 

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and I thought my mileage was bad--I'm getting about 14 mpg combined, with treadwright re-treads that weigh about 55 lbs each.
 
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