This is where you specify tire information. The tire grip coefficient is akin to a friction coefficient. This, along with weight transfer calculated during the run, is what determines traction. Tire grip coefficient typically ranges from .7 to 1 for street tires, but it can be as high as 4 for top fuel dragster tires. If you are not sure of the diameter of a tire you are considering, you can enter the dimensions in the "Tire specifications" area and click "Calculate tire diameter". Any range of growing tires can be used as well. Enter the percent of tire growth at any given speed, and Straightline will automatically change the tire size dynamically during the run.