Oval trackes play with final drive to help handling as well. A lower axle gear can loosen up the back end on turn exit. Don't forget when talking about race engines that top speed is not lower with a lower gear. The problem is whether or not the engine can handle the RPMs without blowing up. I know at Talladega and Daytona some NASCAR teams use a lower gear for more throtle response(top speed is aero limited). Of course some of those cars don't last the 500 miles.
