which pinion?

[trf415]

i have a mad rat and have just bought a 6.5 brushless motor to put in it,
what size pinion should i need for it (standard spur gear)?

thanks in advance

[Shannow]

The rule of thumb is to start low and work up. It depends what surface your running on too - buy a range of pinions and work up in size till it seems right (and check your motor & esc temperature after)

[Battle_axe]

i would say 19/20 ish