⚙️ FDR
Final Drive Ratio — the total gear reduction from motor to wheels.
FDR = (spur ÷ pinion) × internal ratio. Higher FDR = more punch and cooler temps; lower = more top speed and more heat.
What it actually does
Final Drive Ratio is the total gear reduction from motor to wheels — every reduction in the car multiplied together. It is the number that decides whether your car has punch off the line or speed at the far end of the straight, and it is the main lever you have over motor temperature.
In practice
FDR is (spur ÷ pinion) × the internal transmission ratio. A higher FDR means more reduction: more acceleration, lower top speed, and cooler running. A lower FDR does the reverse. Changing the pinion by a single tooth moves FDR meaningfully, which is why it is the usual adjustment.
Worth knowing
Gear for temperature first and speed second. If the motor or ESC comes back too hot to hold comfortably, raise the FDR — heat is what destroys electronics.