HOBBYWING JUSTOCK G2.1 21.5T SENSORED MOTOR (FIXED TIMING) HW30408012

Overview

The Hobbywing XERUN Justock G2.1 21.5T Sensored Motor with fixed timing represents the pinnacle of specification racing motor design, offering competitors and enthusiasts a precision-engineered brushless motor specifically developed for stock and sport class racing. This 540-size brushless motor is the ideal choice for anyone seeking a controlled, reliable power source for their 1/10th or 1/12th scale RC car, whether you're competing in touring car races, drifting events, or enjoying off-road buggy racing. The 21.5T configuration strikes the perfect balance between torque and control, making it an excellent motor for both seasoned racers looking for a practice setup and newcomers to the RC hobby discovering their first serious brushless motor for their RC car UK projects.

Building on the success of the original Justock G2, the G2.1 has been refined with fixed timing and easy-to-use solder joints, eliminating the need for complex timing adjustments and making it an outstanding motor for controlled racing classes where consistency and reliability are paramount. The motor's design complies fully with IFMAR and ROAR specifications, ensuring it meets all competition requirements for Stock and Sport class racing. Whether you're running a competitive touring car, tackling a two-wheel-drive buggy, or exploring rock crawling applications, this sensored brushless RC motor delivers the smooth, linear power delivery that separates championship performances from mediocre runs.

What truly sets the Justock G2.1 apart in the competitive RC car market is its combination of innovative engineering, exceptional build quality, and user-friendly features. The built-in Hall sensor technology paired with a non-adjustable end bell means you get plug-and-play operation without the fuss, whilst the heat-dissipating aluminium case ensures your motor stays cool during intense racing sessions. This is a motor designed by engineers who understand what competitive drivers need: reliability, consistency, and performance you can trust lap after lap.

Key Features

• Fixed Timing Design — The fixed timing eliminates the need for adjustable timing settings, meaning you get immediate, consistent performance without complex tuning. This simplifies setup significantly and makes the motor ideal for stock and sport class racing where timing must remain unchanged, allowing you to focus on driving rather than tinkering with motor adjustments.
• Built-in Hall Sensor Technology — The integrated Hall sensor provides precise rotor position feedback, ensuring your brushless motor delivers smooth, linear acceleration and deceleration without the jerky power delivery some sensored motors exhibit. This sensor integration is critical for technical courses where smooth throttle control determines race outcomes.
• Heat-Resistant Magnet and Aluminium Case — Unlike older iron-core designs, the aluminium case construction offers superior heat dissipation, actively drawing internal heat away from the motor windings and keeping your brushless motor cooler during extended racing sessions. The heat-resistant magnet maintains its magnetic strength even when the motor reaches elevated operating temperatures, preserving performance throughout your race.
• Double Insulated Windings — The dual-layer insulation on the motor windings provides enhanced durability and electrical isolation, protecting the motor against shorts and extending the operational lifespan of your brushless motor even under demanding racing conditions.
• High-Precision Balanced Rotor — Every rotor is meticulously balanced to extremely tight tolerances, ensuring the motor runs with minimal vibration. This precision directly translates to smoother power delivery and reduced wear on your transmission and bearings, maximising the service life of your entire RC car setup.
• Non-Adjustable End Bell with Hall Sensor Integration — The fixed end bell design eliminates timing adjustments entirely whilst keeping the Hall sensor perfectly positioned. This design philosophy reduces setup complexity and potential user error, making the motor more accessible to racers of varying experience levels.
• Silicon O-Ring Seal Protection — A silicon O-ring seal fitted between the end bell and stator serves a dual purpose: it conducts internal heat outward to the motor case for improved cooling efficiency, and it prevents dust and debris from entering the sensitive Hall sensor assembly. This feature is particularly valuable for off-road racing where dust contamination is a constant challenge.
• Low-Impedance Copper Solder Tabs — Rather than relying on connectors, the motor features direct copper solder tabs with exceptionally low electrical impedance at the load end. This allows you to solder your ESC wires directly onto the tabs, creating a solid, high-current-capacity connection that minimises electrical resistance and voltage drop during peak power demands.
• Plug-and-Play Customised 3.5mm Bullet Connectors — When using the motor with compatible ESCs, pre-soldered customised 3.5mm low-impedance bullet connectors provide firm, easy connections between your Electronic Speed Controller and motor, guaranteeing reliable power delivery without the need for difficult rewiring.
• Easily Removable End Bell for Maintenance — The detachable end bell design enables straightforward maintenance and allows you to replace common wearing parts such as the rotor, bearings, and sensor module without sending your motor away for professional service. This rebuilding capability extends the motor's effective lifespan and keeps your racing budget under control.
• High-Precision Japanese Bearings — Both the front and rear bearing positions utilise high-precision Japanese bearings (D9.525×D3.175×t3.967) that spin with minimal friction, contributing to the smooth running characteristics and durability the Justock reputation is built upon.
• Perfect ESC Compatibility — The motor is specifically matched with the Hobbywing XR10 Justock ESC for zero-timing spec racing, and it remains fully compatible with other Hobbywing Electronic Speed Controllers and ESCs from other reputable manufacturers, giving you flexibility in your drivetrain configuration.
• Specifications-Compliant Design — The motor's engineering fully complies with IFMAR and ROAR competition specifications, meaning you can confidently use this motor in sanctioned racing events without worrying about rule violations or equipment rejections at technical inspection.

Technical Performance

The Hobbywing XERUN Justock G2.1 21.5T operates at 2050 KV (revolutions per thousand volts), delivering controlled, linear power perfectly suited to 2-3S LiPo battery configurations commonly used in 1/10th and 1/12th scale racing. With a no-load current draw of just 3 amps, this sensored brushless motor demonstrates exceptional efficiency, minimising unnecessary power consumption and heat generation during idle running. The motor measures 35.9mm in outer diameter with a total length of 52.5mm, making it a standard 540-size brushless motor that fits directly into most modern 1/10th scale on-road and off-road RC car chassis designs. The 3.17mm shaft diameter accommodates standard pinion gears, whilst the motor's weight of 175 grams keeps unsprung rotational mass to a minimum, benefiting handling and acceleration characteristics. The 21.5T configuration represents a balanced turn-count that provides excellent torque whilst maintaining reasonable top-end speed—perfect for technical circuit racing, off-road buggy competition, and rock crawling applications where controlled power delivery matters more than raw speed. The fixed timing design eliminates adjustable timing entirely, guaranteeing consistent performance across multiple heat races and qualifying rounds without requiring mid-event adjustments. The hall sensor integration with 2-pole motor design ensures the electronic speed controller has precise commutation feedback, enabling smooth throttle response that ranges from delicate low-speed control through to full-power acceleration. Whether paired with a 2S LiPo for lightweight racing setups or a 3S LiPo for additional power, this brushless motor scales its performance characteristics appropriately, making it suitable for various racing disciplines including touring car, drift, F1 scale, mini car, buggy, two-wheel-drive short course truck, and even rock crawling applications for those running the higher-torque 21.5T variant.

What's in the Box

• Hobbywing XERUN Justock G2.1 21.5T Sensored Brushless Motor (HW30408012)
• Motor with integrated Hall sensor and fixed timing configuration

What You Need to Complete

• Hobbywing Electronic Speed Controller (XR10 Justock ESC recommended, or compatible alternative)
• 2-3S LiPo battery pack
• LiPo battery charger
• Pinion gear (typically 48-pitch or 64-pitch depending on your chassis)
• Motor mounting hardware (usually included with your RC car chassis)
• If using direct solder connections: solder, soldering iron, and flux (alternatively, use a compatible ESC with 3.5mm bullet connector adapters)
• Hall sensor cable if your ESC requires separate sensor connection (various lengths available: part numbers 30850100, 30810000, 30850102, 30850103)

Frequently Asked Questions

• Is the Hobbywing Justock G2.1 21.5T suitable for beginners to RC racing? — Absolutely. Whilst this motor is competition-grade, its fixed timing design and smooth power delivery make it excellent for newcomers to brushless motors. The absence of timing adjustments actually simplifies setup compared to adjustable-timing competitors, and the sensored design provides predictable, linear throttle response that helps beginners develop consistent driving technique. Many RC clubs recommend this motor for drivers progressing from basic brushed setups to serious brushless racing.
• What battery does the Justock G2.1 21.5T motor require? — This motor is rated for 2-3S LiPo battery packs. A 2S LiPo (7.4V nominal) delivers gentler power suitable for beginners and technical courses, whilst a 3S LiPo (11.1V nominal) provides additional punch for more competitive running. Always ensure your ESC and battery are rated for compatible voltages and currents.
• Can I use this motor with non-Hobbywing ESCs? — Yes. Whilst the Justock G2.1 is optimally matched with the Hobbywing XR10 Justock ESC for zero-timing spec racing, it remains compatible with other Hobbywing Electronic Speed Controllers and ESCs from other reputable manufacturers. The Hall sensor connector is standard, and most modern sensored ESCs will work correctly with this motor.
• What makes the 21.5T variant different from other Justock motor options? — The Justock G2.1 range includes 10.5T, 13.5T, 17.5T, 21.5T, and 25.5T configurations. The 21.5T strikes an excellent balance between torque and speed, making it the most versatile choice for competitive racing. Lower turn counts (10.5T, 13.5T) produce higher speeds but less torque, whilst higher counts (25.5T) sacrifice top speed for maximum pulling power. The 21.5T works brilliantly across on-road touring cars, drifting, off-road buggies, and even rock crawling.
• Why is the fixed timing design beneficial? — Fixed timing eliminates the need for complicated timing adjustments, which can be difficult for less experienced tuners to get right. This simplifies setup, guarantees consistent performance across multiple races, and ensures the motor always operates at its optimum performance point. For competition racing, this consistency is invaluable.
• How do I connect this motor to my ESC? — The motor features low-impedance copper solder tabs designed for direct soldering to your ESC wires, creating a high-current-capacity connection. Alternatively, if your ESC uses 3.5mm bullet connectors, you can utilise the motor's pre-soldered customised connectors for quick plug-and-play connections. The Hall sensor requires a separate sensor cable (available in multiple lengths) connecting to your ESC's sensor input.
• Is this motor suitable for off-road racing? — Definitely. The Justock G2.1 21.5T excels in off-road applications including buggy racing, two-wheel-drive short course truck racing, and rock crawling. The silicon O-ring seal between the end bell and stator actively prevents dust from contaminating the Hall sensor—critical protection for off-road environments where dust and debris are constant challenges.
• How often will I need to maintain this motor? — The detachable end bell design makes routine maintenance straightforward. The silicon O-ring seal minimises dust contamination, but periodic inspection and cleaning—particularly after off-road sessions—will keep the motor running optimally. Common wearing parts like the rotor, bearings, and sensor module can be easily replaced without sending the motor away for professional service.
• Does this motor comply with competition racing rules? — Yes. The Hobbywing XERUN Justock G2.1 is fully compliant with IFMAR and ROAR racing specifications, meaning you can confidently use it in sanctioned Stock and Sport class racing events without equipment restrictions or technical rejections.
• What is the KV rating and what does it mean? — The 2050 KV rating means the motor spins at 2050 revolutions per minute for every volt applied. The 21.5T configuration's lower KV compared to smaller turn-count motors (like the 10.5T at 4000 KV) results in higher torque output and lower top speed—perfect for controlled racing where smooth power delivery and traction are more important than raw velocity.

Why Buy from RC Model Shop?

RC Model Shop is a trusted UK RC retailer and authorised dealer for all the brands we stock, including Traxxas, ARRMA, Losi, FTX, Hobbywing, Spektrum and more. Based in Walsall, we have a physical store where customers are welcome to come in, view products and purchase in store. Whether you are a seasoned competitor, a weekend basher, or just discovering the world of RC for the first time, our team of experienced RC enthusiasts is here to help you find the perfect setup and provide ongoing support. Order the HOBBYWING JUSTOCK G2.1 21.5T SENSORED MOTOR (FIXED TIMING) HW30408012 today with confidence, knowing you are buying from an authorised retailer with genuine products, expert knowledge and a commitment to customer satisfaction. Shop online or visit us in Walsall — we look forward to helping you get the most out of your RC experience.