imjustkoda

I leveled up my 09 f150 and replaced the worn out stock tires with 275/60-20 cooper discovery atp's. I'm using hp tuners to correct the speedometer and i have it where the speedometer in the truck is showing 2 mph less than my gps/ town cops radar gun. I know for the new tire size is 611 revs per mile but I've tried 611, 612, 608, 605, 600 and so on with no effect on it. There is a local tuner in town that sells the super chip x3 handheld and can flash custom tunes on it which I would definitely buy at this point if i knew it would actually put my speedo on point. I know there is a 2-3% room for error but id like to get it closer or at least where my speedo is showing a faster speed than i am going. Any advice or pointers to what I may be doing wrong? Thanks, Dakota.

Mike@Diablosport

iTrader: (2)

No change to the rev per mile setting does anything to the speedo?
In that case, make sure you have disabled the VID block switch for tire size changes.

Thanks