ARRMA Firma 3660 4000Kv 4 Pole Sensorless Brushless Motor: 5mm, SPMXSM5000

The ARRMA Firma 3660 4000Kv motor is a sensorless brushless motor designed for hobbyists needing a direct, dependable power upgrade or replacement for their RC vehicles. Built around a 4-pole rotor configuration, it offers smooth operation and reliable power delivery for compatible chassis setups.

Key construction details focus on convenience and strength. The motor features a 5mm alloy steel output shaft built to withstand torque from sudden acceleration. To save time during installation, it comes with 4mm gold-plated bullet connectors already installed, allowing quick connection to matching electronic speed controls.

Keep in mind the specific limitations of its power rating and design. It operates exclusively on 2S to 3S LiPo battery systems, so it cannot be used with higher-voltage 4S or 6S setups. Because it is a sensorless motor, it may not offer the low-speed crawling smoothness found in sensored alternatives.

Verdict: The ARRMA Firma 3660 4000Kv motor is a solid, straightforward replacement for drivers running 2S to 3S RC builds who want pre-soldered connectors and a durable steel shaft.

• Motor Size: 3660
• Kv Rating: 4000Kv
• Rotor: 4-pole
• Design: Sensorless brushless
• Battery Compatibility: 2-3S LiPo
• Shaft Diameter: 5mm alloy steel
• Connectors: Pre-installed 4mm gold-plated bullet connectors
• Part Number: SPMXSM5000

A great fit if you:

• Run 2S or 3S LiPo battery configurations in your RC vehicle.
• Need a motor with pre-soldered 4mm bullet plugs for quick wiring.
• Use pinions compatible with a 5mm motor shaft.

Consider something else if you:

• Require a high-voltage motor capable of running on 4S or 6S batteries.
• Prefer a sensored motor for fine-tuned, low-speed throttle response.

What battery types can this motor use?
It is compatible with 2S and 3S LiPo power sources.

What is the size of the motor shaft?
It features a 5mm output shaft made of alloy steel.

Does this motor come with wiring connectors attached?
Yes, it comes with pre-installed 4mm gold-plated bullet connectors.