Firma 3900Kv 4-Pole Brushless Motor (SPMXSM3300)

The Firma 3900Kv 4-Pole Brushless Motor is a high-performance upgrade for 1/10-scale four-wheel-drive RC cars, delivering fast, efficient power up to 3S. It features a low-cog 4-pole rotor, a CNC-machined aluminum housing, insulated high-purity copper windings, a hardened 5mm alloy steel output shaft, and precision bearings for durable, smooth rotation. Preinstalled 4mm gold-plated bullet connectors simplify wiring, and it pairs with the Firma 130 Smart ESC for precise, responsive control.

Designed as a direct upgrade for brushed 540- and 550-size motors with the same diameter and mounting pattern (vehicle must accept 5mm bore pinions), this motor uses a robust 4-pole sintered rotor and the same durable construction to deliver strong RPM and torque. It features a hardened 5mm shaft, precision bearings, and a CNC aluminum housing for durability in demanding 1/10-scale 4WD applications. It is SafeD-5 Pinion compatible and compatible with Firma ESCs, including the 130 Smart ESC; the 85A Firma ESC can power it only on 2S power.