Reflash for larger tires...help

[RMarkey]

That small of an increase in tire size shouldn't drop your mpg that much. I went to the 37" MTRs and my actual mpg didn't change that much!

 

[MartyK]

Thanks for the offer tgbol, but I live in Michigan.

 

[Blakers]

Note when speedometers are off, they are not off by a fixed MPH value. It's a common misconception that you can just add or subtract a certain MPH value back to the reading to figure your real speed. It actually works more like a percentage error, so if it's off by 3 MPH at 20, it might be off by 6 MPH at 40 and off by 12 MPH at 80.

Sorry. I should have said at freeway cruising speed. It's now off by a little more than ten percent.

 

[Blakers]

the speedometer accuracy is not the biggest concern it is close cnough to my gps, the drop in fuel mileage is unacceptable (18-19 to 14-15) The tires are 285-70-17 goodyear wrangler mtr. would a less agressive tire be better or would resetting the pinion factor help?

I dropped a little bit Jason. Maybe 1 mpg with the 315 BFG A/T tires. The truck rides, looks, handles, and goes through mud and snow so much better that I don't worry about that slight drop.



I doubt that a less agressive tire would help that much compared to your Wrangers. Now if you ran some smooth tires that were 3" wide with 100 psi, that might help.

 

[MartyK]

I got it taken care of. Friday was a good day. I took a half day off to get the Line-X sprayed in the bed from Line-X of Brighton. Wayne is a good guy to deal with, I highly recommend his shop. While talking to Wayne about my truck I mentioned I still have to get my speedometer recalibrated for the larger tires. He said go across the street to Brighton Dodge they're good. I drove across the street right into the write up area as the drivability tech was walking by. I asked them if they had time to recalibrate a speedometer, they said sure. The tech went and got his scan tool, plugged it in and asked me what I wanted it set to. It took him about 15 minutes to do, and ten of that was spent talking about my truck. The write-up guy said you're all set, no charge. How nice was that, I didn't even buy my truck from them.



Thanks again Wayne (Line-X) and Brighton Dodge.

Marty