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Calculating fuel economy gain from proposed gain in rolling resistance

I calculated my average rolling resistance for all 30 tires as 128. My proposed average will be 93. That's a 28% reduction. How do I take my average fuel economy of 5.7 mpg and calculate how much of a gain from the lower rolling resistance I should receive. Ps: I'm pulling super b 8 axel 60000 lbs empty 135000 - 140000 lbs loaded.

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Most of the online calculators from the tire manufacturers will help you calculate the fuel economy improvement. Put in your old tires vs. the new brands, and the MPG you're currently getting.

Here is the link to Continental's:

ContiCostCalculator

At average driving conditions, rolling resistance accounts for about 35% of your fuel consumption. Of your total rolling resistance, only 15% comes from the steer axle, 42.5% drive and 42.5% trailer.

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You know I am not sure who's right here I looked at the Conti Cost Calculator site then I went to Michelins web site their numbers are different theirs are 18% for steering 30% for drives and 52% for the trailer

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You are right, sorry about that, those #s are for tandem axle trailer. Talked to engineering. In your setup, assuming 20,000 lb steer axle, you are most likely looking at rolling resistance of 14% steer, 24.5% drive, 37% tridem and 24.5% dual trailer. That's if you wanted to be really scientific about it and break out all the axles as ratios of the load.

In the general sense, the contribution of tires to the total fuel economy of a truck is approximately 29% with aerodynamics and drive train losses being the other major factors. To get fuel economy gain, the industry average is to take RR gain divided by 3.5, and that's your percentage of improvement. Real world conditions may vary but that's a general guideline. In your case this works out to a gain from 5.7 to 6.15 (8%). So it looks like you're right on the ball with all your calculations. Hope that helps for future use.

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I'm just guessing here, but the average improvement is close to 1/10 th mpg for every 10 point improvement in rolling resistance for each tandem group. Your looking at 35 points x three groups, (ya I know one is a triaxle) = 1.05 mpg. Don't know I'd expect that much, but 1/2 mpg but be realistic.

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So I can realistically be looking to move from 5.7 to 6.2. And roughly saving 8100 a year. On 120000 miles with fuel at 4.80 an imperial gallon. Did I figure that right?

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What kind of trailers are you dragging? I did super b hopper grain on the prairies for two years. I got 5.1 in the winter and 5.6 imperial mpg in the summer, pulling Wilson smooth walled trailers. It had Michelin XZE tires. So pushing 6 mpg looks like a possibility.

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I'm pulling LPG bottles so I'm heavy all the time. I just figured my June and if I didn't lose any fuel receipts I did a month average of 6.2 imperial. And the trailer is a mix of recaps mostly the sst 225 bandag. Tractor is xdn2 drives and xza3 steers

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Well you might be right on the 42.5% from the drives but that's in a tandem axel trailer, I'm a tridem and a tandem. Two trailers. So I could see the numbers being totally different in an 8 axel configuration.

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Mike will be eternally grateful.
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