The pinion is the small gear on the motor shaft that drives the larger spur gear. Its tooth count sets your gear ratio, which affects top speed and acceleration. A smaller pinion gives more punch, a larger one more top speed.

Steel is strong and affordable for everyday use. Aluminium is lighter and comes in colours, good for saving weight on lower-stress areas. Titanium is light and very strong, popular for racing where every gram counts.

Better bearings cut friction in the drivetrain, so the car rolls freer and the motor works less. Replacing worn or low-grade bearings can improve run time, speed and smoothness. Rubber-sealed bearings also last longer in dirt.

They fine-tune spacing and take slop out between parts, for example setting gear mesh or bearing position. A small stack of shims can remove play from a drivetrain and make it run more precisely.

Match the pitch (such as 48dp or Mod 1.0) to your spur gear, then pick the tooth count for the balance you want. Go smaller for acceleration and cooler running, larger for top speed. Check that your motor and ESC can handle the gearing.