F150_oman

i have just installed new tires with the size 325/65/R18.
banks power pack was installed previously.

according to the tire size calculator, my tires should do 580 Rev's/mile.
after adding this value to the banks power ottomind and upload the program to the car computer, i could not get an accurate speed reading.

example: if the gauge reads 100Km/h my GPS reads 110Km

i tried to increase the value of rev's/mile but there is always a variance.

do i have to keep increasing and trying or decrease ?
or is't possible to have an accurate value?

thanks

PS: 8mm spacers are installed on each of the front tires.

DHFF

I would call banks and ask them. My edge did the same but turned out I put the tires size in wrong and my GPS and speedo read different than the edge. Give them a call I bet they can tell you.