bad mileage due to tires

i finally changed out the stock 265's with a pair of goodyear wrangler mtr's (305 70 R17) I figured that yes i would lose some mileage because of it but i feel that i have lost a lot. I was getting about 14 around town and hardly any freeway driving. Now with these tires i'm doing about 50/50 city/freeway driving and i havent seen 14 yet. Its always about 13. 5. Is this normal and i should just get used to it or what. I have the 3. 73's in the rear. I did not have the speedometer recalibrated cause i didn't think i would need to. Should i get it recalibrated cause i don't know if shift points were mest with at all or not. Anyway what are your guys opinions on this issue.

 

Dont forget to verify speedo error now...



ie. taller tire = slower speedo reading = lower miles traveled = BUT same fuel usage = incorrect MPG



after traveling 100 miles (use mileage markers on interstae) verify odometer distance... . adj mileage with new correction factor (adding the missing miles to the total)-BJ

 

I forget the exact calculation, but I think your new tire size will throw your speedo reading off by about 6-8%, and your distance traveled as well.



13. 5 indicated MPG plus 6% error due to new tire size would be 14. 3 MPG...

 

is this throwing my odometer off aswell and is there a correction to make everything back to normal or what. If so who can do it for me or do i have to buy my own seperate box to correct it.

 

To get the correction made on an '03-'05 truck you need to know the revolutions/mile for the new tires. BFG lists them on their site, Goodyear probably does as well. The tech at the dealer can make the change in the computer for you, it only takes a couple of minutes. 2006 trucks have a different computer system. I had mine changed but I am running 285s which was a choice on the DRB menu because the Power Wagon runs them stock.

 

my speedo was 3-4 miles fast on the freeway. now with 35's its about 5mph slow at 70. i went 10k on stockers and will wait another 10k before i recalibrate.