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Discussion Starter · #1 ·
This has probably been asked before. I can't find it so forgive me if it has.

I'm running an 05 3500 srw auto with 4.10 rear. I tow some , but more miles are driven not towing. My truck is stock and I plan on keeping it that away.

With fuel being what it is I'm trying to get as many mpg as possible.

Would the drop in rpm's going from 265/70/17's to 285/75/17's raise mpg? Or would any gain be canceled out by the added truck height and air drag?
 

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It will not help you on MPG. I'd say you will drop a few hundred RPM's.The big tires will put more of a drag on the truck,wind,rubber on the ground,etc.
 

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I just read an article in diesel world on a project truck, they went up a few tire sizes which lowered the rpm they on ly gained .6 mpg, but at least it wasnt a loss, factory size is a little small a little bigger helps the look IMO
 

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when your speedometer reads 60 you will actually be traveling 62.2 mph. That will lower your gear ratio and you will get better mpg.

I used the calculator here Tire size calculator
 

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smaller tire wwill caue higher RPM...265 and 285s are the right fit for 3.54s
 

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Discussion Starter · #6 ·
I know I'll have to recalibrate my speedometer. this will also calibrate the odometer corectly. After doing this will I see more mpg going from 265/70/17 to 285/75/17 with 4.10 gears?
 

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I know I'll have to recalibrate my speedometer. this will also calibrate the odometer corectly. After doing this will I see more mpg going from 265/70/17 to 285/75/17 with 4.10 gears?
I wouldn't count on seeing an increase. I went from 265s to 285s and didn't see any difference. If there is a difference its so small that its not consistent enough to calculate.

As far as looks go,without a doubt,the 285s will look better.
 

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i tryed it ,no change. and the truck dont handel as well..
 

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My 2G with 285/75/16s was actually acurate as clocked by a radar speed limit sign in town. When I went back to the stock 265's the speedo read fast. I have to clock it again with the 265/70/17's to see where I'm at.
 

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It will not help you on MPG. I'd say you will drop a few hundred RPM's.The big tires will put more of a drag on the truck,wind,rubber on the ground,etc.
what size spacers are you running
 
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