Addforce more powerfull in the air than on ground

Hello! I currently working on some rocket cars and I have come up to an annoying problem. I have cars and ground with a physical material with **0** friction (the car just floats around when adding force). But when I come to a small jump, and the car releases from the floor the car get a massive speed increase, as its colliders (4 sphere colliders for the wheels) leaves the ground, and when it lands again it decreases its speed. It is like the floor has some kind of the drag, but there no friction at all. What could be the problem? Here is my acceleration and steer code // Acceleration rigidbody.AddForce(transform.forward * 3000 * forwardAndBackwardSteer); //forwardAndBackwardSteer is a value, either -1, 0 or 1 (depending on user input) //Rotation Quaternion deltaRotation = Quaternion.Euler(new Vector3(0, 100 * leftAndRightSteer * Time.deltaTime)); rigidbody.MoveRotation(rigidbody.rotation * deltaRotation); //Same thing for leftAndRightSteer