smooth car movement for car game

Hello, I am using built-in unity standard assets for car movement. These also have controls for car movement for mobile games. but the problem that I am facing is that, car is not smoothly moving on the tracks. As it look like I have to give it a lot of force to car to drive it. I am asking this question because now a days most of the car games have really smooth moving car as it look like they are floating in the air (above 10cm of road). So can anyone suggest me how can I move or drive my car as smoothly as we see in other car games?