[Fester]

Just a real silly question. When adjusting the speedo for tire tires do you use the tire sheet's spec for the diameter or actually measure from the ground when they are on the car? I am moving up from 245/45R20 on my RT to 255/45R20 and I want to get the speedo settings right using the tuner.

 

[mnunes]

The most accurate way is to measure the tires from the ground to the top of the tire.

 

[Mango Daytona]

Just plug in the tire size, the system will know the difference between what was stock and what would be on it now.