best setup for a 9t brushless
 

whats the best pinnon etc to run in my macnum to run a ezrun 9t?

your best bet is a 21/22 with a 80 spur

ive only got a 86t spur mate

than put a 17/19 T pinion. But you can find good gear ratio calculators in the internet. I don't find now the one that I am using, cas it is on my laptop. But what you have to know is that the Mad Rats internal ratio is 2,6. So you only have to add the spur gear in one of the boxes and find the perfect T number pinon for a perfect gearing

for ex:
http://dhrc.rchomepage.com/RolloutCalc.htm

like he said a 19 then would be fine although really a 18 would be better