⚙️ Pinion
The small gear on the motor shaft. More teeth = more top speed (and heat); fewer = more acceleration.
What it actually does
The pinion is the small metal gear on the motor shaft, and it is the first thing anyone changes to alter how a car drives. Its tooth count, paired with the spur gear, sets the final drive ratio — and therefore acceleration, top speed and running temperature.
In practice
A larger pinion lowers the FDR: more top speed, less acceleration, more heat. A smaller pinion raises it: more punch, lower top speed, cooler running. One tooth is a meaningful change, which is why pinions are sold in single-tooth steps.
Worth knowing
Reset the gear mesh every time you change pinion, and check the grub screw is on the flat of the motor shaft with thread lock. A pinion that walks off its shaft mid-run takes the spur with it.