What is a good Pinion/Spur to run for racing. I believe right now I'm running the 18/54 with the normal Velineon Brushless motor/esc and I have the Venom Sport Power 5000 40c 7.4v battery. But I am fixin to upgrade to the Castle Creations Mamba Max Race Pro SCT System ESC 2400kv 1415. So which Pinion/Spur combo should I get?