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Discussion Starter · #1 ·
The dealer said the 07 6.7 would not go up to a 35 tire size. I tried the SC Cortex and it still adjust my speedometer. Does this throw my mileage off. I'am normally show about 12 to 14 mpg. Any answers.
 

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simple... look up the tire data for your new tires, and find the rolling circumference or the revolutions per mile. Find the same numbers for the stock tires, and divide the new tire number by the old tire number. This should give you a number bigger than 1. I did this with 37's, and came up with 1.17. Take that number and multiply your odometer reading by it before dividing by gallons used. It translated into almost 2mpg for 37's. Most guys are losing 3mpg with 37's, 2 from calculation error and 1 from bigger tires that take more fuel to move and push through air. If you can't find the actual revolutions per mile data, just use the listed diameters to get close. Air pressures make a small difference too.
 

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bart9505, I'm not sure that calculation is correct. I went to a tire size calculator on the web and put my stock size tire (265s) and also my new tire size (285s) and it told me the difference was 3.5% and that my speedo would be 2 mph off at 65 mph. I think you are probably closer to a 5 or 6% differential. Maybe even more....
 

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I used my gps and it says i am going 76mph when my speedo says 70mph:w:
i went from 265,s to 35's
 

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I've heard that the overhead consoles aren't very acurate. I figure the math.... miles traveled divided by gallons. Usually has to be on a fill up.
 

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I used my gps and it says i am going 76mph when my speedo says 70mph:w:
i went from 265,s to 35's
Same here with my truck & 35's.
 

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Discussion Starter · #8 ·
mileage

but if the speed is wrong so should the mileage on the truck. I would think. So when doing the mileage by hand. Wouldn't the nembers be wrong and by what percentage? My truck at 60 mph is actually going 66 mph. The faster you go the futher off the numbers seem.
 

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I add 10 miles for every 100 miles i drive so if my trip meter says 350 i add 35=383/# of gls of fuel added at fill up and there you have it....i got this # by zeroing out the the trip meter and my gps then drove till trip said 100 miles and gps then said 110miles:CRY:
 

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Discussion Starter · #10 ·
mileage

Thanks I think that is what I'am going to start doing. When I purchase my truck I was gettin 17 to 19 on hwy by the overhead. When I put the larger tires on and started to hand figure my mileage. It did not seem like I would lose aobut 4 mpg. I could understand 1 or 2 but not 4 or 5. If I would add about 10% that would avg. about 15 to 17 hwy. Alot better than I was thing it was getting.Thanks for all your help.
 

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I add 10 miles for every 100 miles i drive so if my trip meter says 350 i add 35=383/# of gls of fuel added at fill up and there you have it....i got this # by zeroing out the the trip meter and my gps then drove till trip said 100 miles and gps then said 110miles:CRY:
This is exactly what I do, just add 10% to whatever the odometer says to get actual mileage.
 

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i bought a power pup and corrected my speedometer instead. now, when my speedometer reads 70mph, my GPS reads 70mph. i didn't like the idea that i was putting more miles on the truck than the odometer indicated. it just felt...dishonest.
 

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I also have 35's. I figure it's about 8% off... Take your total miles on the tank and multiply it by 1.08 (that's 108% of the tripometer) and it will get you close.
 

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Does the Edge do Speedo correction????????? or does it just tell you what the correct speed is on its display!!!!
 

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Discussion Starter · #16 ·
edge

The edge juice only tells the corect speed you are traveling. It configures the height of the tire and adust the speed on the display of the edge.
 
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