we don't run a rear bar in our circle track cars and my friend who drives in the nascar canadian tire series they don't have rear bar on the circle track or road course cars. I read that nascar is trying to set up a rear bar in their cup cars but they don't run them yet. Setting up a car is difficult enough for us trying to get the wedge, the weight on each wheel, the weight bias left to right and front to back without a rear bar messing it up.