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Old 07-05-2013, 02:47 AM
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What's killing my mpg

Recently switched from a set of 34.8x12R22 +12 offset terra grapplers to a set of 35x13.50R18 -12 offset Mickey Thompson mtz.

Is it the width, the tread pattern, the change in offset, or the weight difference in the tires?

Went from 19.2 hand calculated to 16.1 hand calculated.

Andrew


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Old 07-05-2013, 03:48 PM
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Offset doesnt have anything to do with mpg, the tread and width will be your main culprits. Your weight should have gone down as you went from a 22" rim to a 18" in most cases. Try with another tank and see what numbers your getting.
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Old 07-05-2013, 04:58 PM
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Quote:
Originally Posted by heisman01 View Post
Offset doesnt have anything to do with mpg, the tread and width will be your main culprits. Your weight should have gone down as you went from a 22" rim to a 18" in most cases. Try with another tank and see what numbers your getting.
I went from 365/65-16 Toyos to 315/75-16 BFGs and thought for sure I would pick some mpg due to the weight loss, nope! Therefore, I think another tank or two would be a good idea.
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Old 07-05-2013, 06:17 PM
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Quote:
Originally Posted by heisman01 View Post
Offset doesnt have anything to do with mpg, the tread and width will be your main culprits. Your weight should have gone down as you went from a 22" rim to a 18" in most cases. Try with another tank and see what numbers your getting.
Offset does come into play when your going from stock, to an extreme -offset. But in this case I would say width is the biggest killer.
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Old 07-05-2013, 06:34 PM
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Probably a heavier combo... More rolling resistance, air pressure in the tire. Load range, etc.
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Old 07-06-2013, 01:33 PM
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Both tires were load range E, been through 6 tanks with these tires nothing has changed about my driving habits yet I'm getting a significant drop in mpg. The width is roughly 1 inch wider than my old pair. In guessing its weight and or tread related


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Old 07-06-2013, 01:47 PM
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35's will bring down your mpg
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Old 07-06-2013, 02:43 PM
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The tires are too similar to cause that drastic of a change, it could be that your brakes are dragging.

What method are you using to hand calculate your mileage?
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Old 07-07-2013, 05:54 AM
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I've checked just about everything brake wise. To calculate my MPG I use my GPS to track how many miles I've travleled. When I fill up I set my GPS to 0 miles then keep it on any time I'm driving, then when I fill up again I take the number of miles I traveled and divide it by the number of gallons the truck took.

I thought it was too similar of a tire size too but I took a look at the weight difference and I'm thinking more and more that its the weight that's killing me.
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Old 07-07-2013, 06:27 AM
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The only thing that I could offer to your calculations is to do a couple of tanks filling until you can see the fuel in the neck. Yes this sounds anal, but it ensures that the same about was put in.

Other than that, I am at a complete loss as to why as well. As I stated earlier, I went from a 14.50 DOWN to a 12.50 and observed NO change in mpg. I thought for sure that I would have seen an increase due to the weight difference, but my truck proved me wrong.

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