OK, So I have been playing with the SC3865, so far, not too shabby (Mileage tune is a no go due to db error, but they are working on it...)

My default tire diameter on "stock" was set to 29 inches....my truck came with the Goodyear Wrangler 265-70-16s...spec has these at 30.6 inches, actual on the truck (with wear, pressure, etc) is 29.75.

Just wondering what setting was default on your truck? Perhaps this is one of the reasons my mileage was so bad

Hammond

 

Mine was/is 28.00 inches with 245/70/16 Firestone Destination A/Ts. No need for me to change it, but I did make sure it was accurate.

Our trucks came with 2 sizes from the factory, 245/70 or 265/70. Superchips must be able to recognize that your truck has the bigger size, they just dont have the tire size big enough.

PS- Fill it up with 91 and go performance!

 

Did you measure it at 28 inches? That seems a little small for 245/70/16...
Anyone else care to measure? Now I am curious!

Measure from the ground to the highest point of the tire (use a ruler across the tread, and a tape from the ground to the ruler).

 

Using a tape measure I get 28" exactly from the ground going across the center of the tire. The speedo is on as far as I know as well. Its close to the radar trailers that the local police departments set up on the side of the road to show your speed.