Brushless gearing advice

[c0sie]

I understand the theory behind how to gear a brushed motor optimally, but ever since going over to BL ive had issues trying to understand the theory behind gearing my brushless systems.

For example...if you undergear a brushless significantly (say by 3 or 4 teeth) what would that do to acceleration, top speed and temperatures?

The same question for over gearing.

How do you figure out the optimum gearing to run on a brushless?

Thanks in advance