Help gearing a tamiya f103gt
 

i am getting a brushless system which is classed as a 13t and im going to get an 80(ish) tooth 64dp spur gear but i dont have a clue about what pinions to use, i know that ill probably have to do some fine tuning, but ive been told a way of roughly finding a close pinion quickly but i've forgot how to.
any help on finding a way of finding the pinion to use would be appreciated

thanks, lee

i've forgot to mentions that it is on my tamiya f103gt direct drive chassis

and again, any help will be appreciated