Gearing for a 1900kv motor.

[suicideneil]

What esc are you using?

What motor is it exactly?

I would say though that with the BL Emaxx's 6.3" tires ( I assume you are using those ), something like 20-22/68 gearing will be fine for ~40mph topspeed- adjust gearing up or down depending on motor/esc & battery temps ( hot motor + cool esc = gear up, cool motor + hot esc = gear down, hot everything = gear down ).