Mileage drop with new tires

[Oongawah]

Just put on 285's(look great).

Will be installing 265's again next time. I lost my sweet spot, and dropped about 4 miles to the gallon(not considering ratio). I don't hold 5th as well on the steepest of hills anymore. One more factor would be that big Ol' heavy TransFlow Midship Tank(45 Gal.) I just had installed. Just a thought. Take care, Chuck.

[GMC-2002-Dmax]

Originally posted by Oongawah:
Just put on 285's(look great).

Will be installing 265's again next time. I lost my sweet spot, and dropped about 4 miles to the gallon(not considering ratio). I don't hold 5th as well on the steepest of hills anymore. One more factor would be that big Ol' heavy TransFlow Midship Tank(45 Gal.) I just had installed. Just a thought. Take care, Chuck. I had 285's and when I put them on I went from 18.5-20 mpg to 15.5-16 using the odometer for mileage calculations. I figured my mph and miles driven were off on avg 6-8%. If I add that back into the equation I lost 1.5 mpg or so.

I now have a Predator v1.04 so I will reflash for my in 305/70-17"'s when I get them mounted on the H2 wheels late next week and then post true results.

GMC
;)

[DMAXTODD]

I am not a math guy.. What is the difference between 245 and 265 when calculating mileage, my last tank was 16.8,what would this be corrected for 265's?

[DMG]

Going from 245's to 265's, you need to increase you odometer reading by approximately 3.9% to calculated your mileage. Also, regard operating performance, you are going to effectively changing the gear ratio from 3.73 to approximatley 3.58 with the larger tires, which would adversely effect the pulling performance.