Howdy guys, I have a 2001 F150 4.6 and an edge tuner on stage two. When I was home for easter I had a lot of time on my hands so I decided to do a custom tune partly because my spedo is off. When I bought the truck in October, the Stealership was tellin' me that the tires were new, which they were, but they put smaller cheaper tires on the truck than are supposed to be. My Edge told me during the programing that Tire Size, was "Not able to be performed." I am getting 31's once I put the lift on my truck so that is gonna kill the spedo even worse but in the wrong direction, at least now I don't speed as much cuz I look and think i'm going faster than I am. How can I fix it so that I can tune the tires to fix the spedo?
~Phil

 

you cannot change the tire size as far as I know. I have contacted edge about this and have still not got a reply. the fix that I have found is by tricking the pcm to thinking otherwise. I changed the gear ratio in the chip from the stock calibration which comes up as 3.31 to 3.23 I am running 285/75 R 16 I know that its not much difference but I was off as much as 5 mph with both the edge and stock speedo. if you have a 3.55 gear ratio try 3.23 for the gear ratio in the edge and double check if it fixed it with a gps and then adjust from there. It worked for me i'm only .08 mph off between the gps and the speedo in the truck good luck. any questions ask me Im more than happy to help. Oh and I'm running in program 3 and I'm getting about 17 Average Miles Per Gallon according to the EDGE programmer better than most on here.