Perfect friction with WheelColliders

Hello, Iam playing around with WheelColliders and I have a problem with the car not being any faster if I add more power to it. The problem is, the wheels are spinning. I need to improve friction on wheels so they dont spin through and the car moves forward exactly the distance that the wheel has turned. There is a friction curve for that, but for the life of me I, I cant figure out how it works. When I set it to zero, the wheels turn and the car doesnt move at all. What is the perfect setting for this? Thank you for any tips.