The Spektrum P-SPMXSM1200 Firma 1250Kv brushless motor with 5mm hardened steel shaft and 6.5mm bullet connectors is engineered for high-performance 1/7–1/5 scale RC platforms that demand uncompromising speed, torque, and thermal stability. Designed with a 4685-size inrunner architecture, this sensorless motor delivers up to 180A continuous current and 4190W output, making it an ideal upgrade for large-scale builds powered by 8S LiPo setups. With a CNC-machined aluminum housing, high-purity copper windings, and precision bearings, the Spektrum P-SPMXSM1200 offers a refined balance of durability and efficiency for serious RC enthusiasts.
Key features of the Spektrum Firma 1250Kv brushless motor
- High-efficiency rotor – delivers 90% energy conversion for extended runtime and reduced heat buildup
- 5mm hardened steel shaft – ensures torque stability and long-term durability under high load
- 4685-size inrunner design – compact yet powerful configuration for large-scale RC platforms
- 180A continuous current – supports aggressive acceleration and sustained high-speed operation
- Preinstalled 6.5mm bullet connectors – enables fast, solder-free installation with secure power delivery
- Low cog rotor – improves throttle smoothness and reduces startup resistance
- Precision ball bearings – minimize friction and enhance rotational stability at high RPM
Why is the Spektrum P-SPMXSM1200 ideal for large-scale RC platforms?
The Spektrum sensorless motor for 1/7–1/5 scale RC vehicles with CNC aluminum housing and 90% efficiency is purpose-built for demanding applications where power and reliability are non-negotiable. Its 4685-size inrunner configuration fits seamlessly into larger chassis formats, including the ARRMA Limitless Speed Roller. With a robust 180A continuous current rating and 4190W output capacity, this motor is capable of delivering sustained performance across extended runs. The 84mm length and 618g weight provide a stable center of gravity, while the 5mm alloy steel shaft ensures consistent torque transfer under stress.
How does the rotor design improve performance?
At the heart of the Spektrum 4685-size inrunner motor with 4-pole rotor, 180A continuous current, and 4190W output lies a low cog 4-pole, 8-magnet rotor engineered for smooth throttle response and minimal startup resistance. This design reduces mechanical drag and enhances torque modulation, especially during rapid acceleration. The sintered rotor construction ensures magnetic integrity under high RPM conditions, while the high-purity copper windings maximize electrical efficiency. Together, these elements contribute to the motor’s 90% energy conversion rate, translating into longer runtimes and cooler operation.
What makes the installation process so efficient?
The brushless inrunner motor with 10 AWG leads, alloy steel shaft, and high-purity copper windings is designed for plug-and-play convenience. Preinstalled 6.5mm gold-plated bullet connectors eliminate the need for soldering, allowing users to integrate the motor quickly into existing setups. The 10 AWG leads provide low-resistance current flow, supporting high-amperage demands without voltage drop. This streamlined installation process is especially beneficial for racers and hobbyists who prioritize speed and simplicity when upgrading their vehicles.
Is the Spektrum P-SPMXSM1200 compatible with 8S LiPo setups?
Yes. The Spektrum P-SPMXSM1200 with 12–35.2V input range, 84mm length, and 618g weight for large-scale installs is optimized for high-voltage configurations, including 8S LiPo systems. With an input voltage range spanning 12V to 35.2V, this motor accommodates a wide spectrum of power sources while maintaining consistent performance. Its compatibility with the Spektrum Firma 160 Smart ESC ensures seamless integration and optimal power management. Whether you're building a speed run monster or a drag racing rig, this motor delivers the voltage headroom and current capacity needed for extreme setups.
How does the shaft construction contribute to durability?
The hardened steel 5mm shaft featured in the Spektrum digital inrunner motor with 180A continuous current, 4-pole rotor, and CNC-machined housing is engineered for long-term resilience. Alloy steel resists deformation under torque stress, while the 3/16" diameter provides a robust interface with drivetrain components. This shaft design is particularly valuable in high-speed applications where rotational forces are intense and sustained. Combined with precision ball bearings, the shaft ensures smooth operation and minimal wear over time.
What makes this motor a strong match for the ARRMA Limitless Speed Roller?
The high-RPM motor for ARRMA Limitless Speed Roller with sintered rotor, precision bearings, and low cog design is perfectly suited for platforms that demand high-speed stability and thermal efficiency. Its compact 4685-size form factor fits cleanly into the Limitless chassis, while the low cog rotor enhances throttle control during launch and acceleration. The CNC-machined aluminum housing dissipates heat effectively, and the 4190W output ensures that the motor can handle aggressive gearing and extended full-throttle runs. For builders seeking a reliable upgrade path, this motor offers a balance of power, precision, and ease of installation.
How does the Spektrum P-SPMXSM1200 maintain efficiency under load?
Efficiency is a standout feature of the Spektrum P-SPMXSM1200 Firma 1250Kv brushless motor with 5mm hardened steel shaft and 6.5mm bullet connectors. With a 90% energy conversion rate, the motor minimizes wasted power and heat buildup, even during prolonged use. The combination of high-purity copper windings, precision bearings, and optimized rotor geometry ensures that electrical input is translated into mechanical output with minimal loss. This efficiency not only extends battery life but also reduces thermal strain on surrounding components, making it a dependable choice for high-demand RC builds.
Buy Spektrum Firma 1250Kv brushless motor for 8S-powered 1/7–1/5 scale RC speed platforms.
Brand, Model and Product Type
- Brand – Spektrum
- Model – P-SPMXSM1200
- Product Type – Spektrum P-SPMXSM1200 Firma 1250Kv brushless motor with 5mm hardened steel shaft and 6.5mm bullet connectors, Spektrum 4685-size inrunner motor with 4-pole rotor, 180A continuous current, and 4190W output, Spektrum sensorless motor for 1/7–1/5 scale RC vehicles with CNC aluminum housing and 90% efficiency, Spektrum with 12–35.2V input range, 84cm length, and 618g weight for large-scale installs, Brushless inrunner motor with 10 AWG leads, alloy steel shaft, and high-purity copper windings
Dimensions
- Product length – 8.4 cm, suitable for large-scale RC platforms requiring extended motor housing
- Outer diameter – 4.6 cm, standard for 4685-size inrunner motors used in 1/7–1/5 scale vehicles
- Product weight – 618 g, provides stability and torque balance in high-speed RC setups
Motor Design and Performance
- Motor type – Brushless sensorless configuration for high-RPM and low-maintenance operation
- Motor size – 4685 inrunner format, optimized for compact yet powerful integration
- Rotor type – 4-pole sintered rotor with low cog design for smoother throttle response
- Maximum continuous current – 180A, supports aggressive acceleration and sustained power delivery
- Power output – 4190W (on 6S), ideal for speed-focused builds and drag racing platforms
- Efficiency – 90% conversion rate, minimizes heat and maximizes runtime
Materials and Construction
- Housing – CNC-machined aluminum for enhanced heat dissipation and structural integrity
- Shaft diameter – 0.5 cm (5mm), hardened alloy steel for torque stability and drivetrain compatibility
- Windings – High-purity copper for efficient current flow and thermal control
- Bearings – Precision ball bearings for smooth rotation and reduced friction at high RPM
Connectivity and Installation
- Connector type – 6.5mm gold-plated bullet connectors, preinstalled for fast, solder-free setup
- Wire gauge – 10 AWG leads, supports high-current flow with minimal resistance
- Drop-in fitment – Compatible with ARRMA Limitless Speed Roller and other large-scale RC platforms
Electrical Compatibility
- Input voltage range – 12V to 35.2V, supports 8S LiPo configurations for extreme performance
- Recommended ESC – Spektrum Firma 160 Smart ESC, matched for optimal power handling and telemetry
What’s in the Box
- 1 × Spektrum Firma 4685-1250Kv Sensorless Brushless Motor
- 1 × Set of 6.5mm Gold-Plated Bullet Connectors (preinstalled)
What You Require / What You Will Need
- Electronic Speed Control such as the Spektrum Firma 160 Smart ESC
Warranty
- Warranty information is not provided in manufacturer documentation and is therefore excluded
