Kyosho IFW167 50T Lightweight Spur Gear ST-R

A 50 tooth lightweight spur gear for Kyosho's Inferno ST-R and related platforms.

The spur gear takes drive from the clutch bell and passes it into the centre differential, so it sits at the point where all of the engine's power enters the drivetrain. Tooth count sets the final drive ratio alongside the clutch bell, which is the main lever you have for matching the car to a track: fewer teeth gears the car taller for top speed, more teeth gears it down for acceleration and lower running temperatures.

The lightweight designation matters because this is rotating mass sitting in the middle of the drivetrain. Weight removed from a component that spins at high speed pays back more than the same weight taken off the chassis, since the engine has to accelerate it on every corner exit.

Spur gears are also consumables. The tooth faces wear, and a spur that has been run against a worn clutch bell wears faster still, which is why the pair are usually replaced together. Always reset gear mesh after fitting a new spur.

Dealers list fitment across the Inferno ST-R, ST-RR, MP-7.5 and MP777.