I used 37 volts with my truck and I blew the diffs. Even if you drop to a 14 tooth pinion, you will still go over 55MPH. That is fast and too fast if you plan on racing. You should try a 4S lipo with the 14 tooth and it should put you right at around 40MPH. I love power and speed, but you will have to stock up on parts for sure.