The thing is.... your tire size is programmed into the computer to give you accurate speedo readings. Reseting the computer doesn't change this setting. If its programmed for 265/75/16 or what ever came stock, going with a 285/75/16 means that your not recording as many miles as you are covering (your recording less). that means your mpg (I assume your going off the computer generated) is not being accurately given. Not to mention its not that accurate to being with, but the small difference that did show is actually bigger than its telling you because it assumes your running as smaller tire.

 

so i did a check and i actually have 225 75 r16s

 

I have figure it has to be pretty accurate though. My truck stock comes off the lot with 275/70/17 tires. So a 285/70/17 shouldn't be making much of a difference, right? 4.10 gearing with 285 tires is pretty much a dead on combo. Even said, I'm averaging 11.5mpg....which to me, sucks. This is why I plan to raise this truck up and put big tires back on it again. I say this because my gas mileage sucks still even with 285s, so I might as well be enjoying the look of huge tires while I'm getting ****ty gas mileage. I will only get big tires though, IF, I get an APS...

 

Yea there isnt that much difference to worry about. It slipped my mind that you do have the offroad for a sec lol. Just forget I mentioned anything until you throw those 35's back on. I know for me to throw on 285's, it throws the speedo off 6mph at some point. And for me if I don't recalibrate the computer for the new tire size, the computer wouldn't see about 7.32 miles-ish for every 100 that I put on when calculating off my current tire, and a 285 of the same brand.

 

This is why I suggest gearing. In his case, he has 3.55 gearing. I wouldn't waste my money going to a 3.93. I'd spend the money on 4.10s. Then you'll notice something.

 

i have the 3.93's and wish mine was a little lower. 4.10. or 4.56 if you donnt do a lot of interstate driving.