New Larger Tires, Fuel Mileage and Computer Calibration Help

[jmontz32]

I searched this forum and google as well before I decided to start a new thread but had no luck finding my answer.

 

 

So, I just put on new, larger tires today and a 2" level kit. I went with the Toyo AT 2 XT in 295/55/20 and kept my stock 20" wheels. The stock tires are 31.9' tall and the new Toyo tires are 32.8" tall and have 21 fewer revs per mile. My fuel mileage on my trucks screen has seemed to take a huge hit. I expected to take somewhat of a hit on mileage but not this much. My questions are as follows.... is the mileage on screen inaccurate due to the change in tire size, which would mean Im not really taking that big of a mileage hit?? Where can I get my computer recalibrated to reflect the new tire size?? Thanks in advance for any help you all give me.

 

 

 

thats the exact tire I'm looking at putting. can you post a pic?