Hey guys, at the moment im a bit stuck with trying to get a accurate speedo reading for my car, as i have changed the wheels and diff ratio,

Standard fitment is: 205/65/15 tyres and 3.08:1 diff ratio

I have changed to: 235/40/18 tyres and 3.46:1 diff ratio,

the stock value for the 205/65/15 tyres and 3.08 diff is 6200ppk

now im stuck trying to work out a correct ppk value for the 235/40/18 tyres and 3.46 diff,


if any of you guys have a formula to work out the new ppk, it would be really appreciated for any assistance,

cheers
andrew