Car keep moving when wheel collider motor torque zero

Unity Engine
1

Car still moving when motor = 0

public void FixedUpdate()
    {
        foreach (AxleInfo axleInfo in axleInfos)
        {
            if (axleInfo.steering)
            {
                axleInfo.leftWheel.steerAngle = steering;
                axleInfo.rightWheel.steerAngle = steering;
            }
            if (axleInfo.motor)
            {
                axleInfo.leftWheel.motorTorque = motor;
                axleInfo.rightWheel.motorTorque = motor;

               
            }
           
            if(motor==0)
            {
                axleInfo.leftWheelAnimator.speed = 0;
                axleInfo.rightWheelAnimator.speed = 0;               
            }
            else
            {
                axleInfo.leftWheelAnimator.speed = 1;
                axleInfo.rightWheelAnimator.speed = 1;
            }           
        }
    }
2

Can’t see anything wrong…

3

Shouldn’t the tank stop moving in few secs when motortorque zero( track animation stop)? It keeps moving forever. I also find similar problem in the car sample scene, the car “slide” very long distance after motor torque become zero.

4

I think I solve the sliding problem by adding infinity brake torque. (very high brake torque do not work)

But I find a new problem now, the acceleration is awful. Motor torque do not increase the tank velocity, and wheel rpm is read only. How can i accelerate it?

 if (motor == 0)
                {
                    axleInfo.leftWheel.brakeTorque = Mathf.Infinity;
                    axleInfo.rightWheel.brakeTorque = Mathf.Infinity;
                }
                else
                {
                    axleInfo.leftWheel.brakeTorque = 0;
                    axleInfo.rightWheel.brakeTorque = 0;
                }