The ideal ratio depends on the car and track being used, if you don't know how to set them up use the auto set and if it's a low Bhp car 25-30 is usually ok, a higher Bhp car should be set in the 30's around 35 is usually a safe bet. The higher setting the better it will be for a fast track so always check on the test course cos if you dont go fast enough you'll lose.