^+1. Heat is the biggest determining factor in gearing for electric racing (considering the performance is on par with expectations). But you'll also want to take in to consideration timing (end-can and ESC). Both can make a sizable difference in your ultimate gearing. Start around 26-30 with timing, and 30+ without and see where the temps fall. If they are high drop a tooth or two, if they are low add a tooth or two.

My B4 baselines
-75/32 no timing
-75/26 with timing

Just note, when opening thread about electric racing it may be best to open in the electric racing portion of the forum. It helps you to get your question seen by the right people.