It depends alot on your rear spring rates, if it is already pretty stiff, the rear bar can cause varying amounts of oversteer depending on bar stiffness. I have a nice rear bar on my road racing car with a solid rear axle, and disconnected it after the first practice session 3 years ago and haven't used it since, way to much oversteer. I am sprung pretty stiff though. I am probably 1 to 2 seconds a lap faster with the thing disconnected. If you have a comfy riding setup, the bar would probably help.