I own a serpent s400 and a serpent s120. I have no idea of what pinion gears have to fit those cars.
My s400 has an lrp sphere tc with a 4.5t motor and the stock spur gear which if am not mistaken is 102t. The car has so mush accelaration that makes it spin when coming out of corners. i tried different setups and the torque and power of this brushless is amazing. At the begining i was using a 32 pinion gear and then i changed to 34 and i had beter top end along with slightly smoother accelaration. I use -100 exponential on my remote so that i will be able to drive it. also when i had the 32 the motor and speed controler were very hot.
Now i have a s120 and i dont know which pinion gear i must use..
i never used it before so am not sure how this pan cars work..
I will be using 12x2 motor i think with a cheap chinese speed controler.
I also have a brushless system for it but i suspect it will be very fast for that tiny car.