Overview
Amped-up ARRMA® RC blasting gets "fun-sized" with the fast, tough, and ready-to-run GRANITE™ GROM 4X4 Monster Truck. At 1/18 scale, it's small enough to take along anywhere, yet it delivers a big dose of genuine ARRMA performance and durability whenever you get the urge to bash. Whether you're a young beginner discovering the world of RC cars for the first time or an experienced RC basher looking for a convenient, high-quality ready to run RC model, the GRANITE GROM easily fits into your lifestyle. Unlike many manufacturers of mini RC models, ARRMA made no compromises when shrinking this basher down to small scale size—the GRANITE GROM 4X4 Monster Truck is precision-engineered to the same high standards as larger ARRMA RC vehicles.
Enjoy some after-school RC monster truck action with friends. Sneak in a little bashing during your office lunch break. Take it on holiday, keep it in your car, or stash it in your desk drawer. The GRANITE GROM is small in scale but enormous in capability, making it perfect for anyone seeking genuine ARRMA toughness for anyone, anytime, anywhere. Whether you're exploring the world of brushed RC cars or stepping up to a higher-quality small scale RC truck, this ready to run RC model offers exceptional value and versatility without demanding a huge commitment of space or time.
It's tough, fast—and conveniently small. Among small scale RC basher models it's in a league of its own, with convenience plus the power, strength, and handling capabilities you need to get serious about your stunts. The ARRMA GRANITE GROM 4X4 Monster Truck endures any punishment you can dish out, whether you're bashing in the garden, at the park, or on the beach.
Key Features
- Clipless Body Fitting System (Patent Applied) — The GRANITE GROM features an innovative clipless body mount design that keeps the body securely attached but makes removal and re-installation incredibly easy and secure without the need for body clips or tools. This means users of all ages can successfully manage body attachment and removal, whether you're swapping colours or accessing the chassis for maintenance.
- Compact 1/18 Scale Design — At just 250mm in length and weighing only 800g with battery included, the GRANITE GROM is nearly half the size of the 1/10 scale GRANITE, making it genuinely portable whilst maintaining full-sized durability and performance characteristics that serious RC enthusiasts demand.
- Shaft-Driven 4WD Drivetrain — The four-wheel drive transmission with robust metal gears carries power from the MEGA 380 brushed motor through an enclosed drivetrain to the tough dBoots® FORTRESS™ monster truck wheels and tyres, providing maximum traction and durability across all terrains.
- Full Metal Gears Throughout — All-metal drivetrain and servo components ensure maximum durability during hard bashing. The spur and crown gears are metal construction, and even the installed Spektrum SX110 steering servo features tough metal gears for carefree operation in any conditions.
- Precision Moulded Composite Chassis — The rigid moulded composite chassis provides go-anywhere toughness and excellent durability, engineered to handle the rigours of serious bashing without unnecessary weight.
- Impact-Absorbing Bumpers — Front and rear bumper systems with integrated bumper loops help the GRANITE GROM soak up the rough and tumble of hard bashing, protecting vital components and extending the lifespan of your investment.
- Oil-Filled Telescopic Shock Absorbers — Independent suspension with oil-filled, coil-over shocks allows the GRANITE GROM to soak up any terrain, with standard silicone oil at 300 cSt viscosity for smooth, controlled suspension performance.
- Waterproof Electronics System — Both the Spektrum 2-in-1 ESC/receiver and the Spektrum SX110 servo are fully waterproof, enabling carefree bashing in any conditions including wet weather, muddy terrain, and water crossings.
- Spektrum SX110 Waterproof Servo — Powerful, fast, and featuring full metal gears, this waterproof servo delivers the precise steering control needed for responsive handling and advanced stunts, with metal servo gears for extreme durability.
- Torquey MEGA 380 28T Brushed Motor — The compact 380-size brushed motor is perfectly sized to fit the GRANITE GROM whilst delivering sufficient torque to tackle any surface, from grass and gravel to concrete and dirt.
- Spektrum 2-in-1 ESC/Receiver Unit — The integrated 25A waterproof ESC and Spektrum 2625RX receiver provides smooth, proportional control with waterproof, go-anywhere performance, using the IC2 connector standard for reliable power delivery.
- Spektrum SLT2 Transmitter with Throttle Limiters — The 2.4GHz radio system includes adjustable 50% and 75% throttle limiters that let you easily match speed to your skills, making this an ideal ready to run RC car for beginners learning control techniques safely.
- Ergonomic Transmitter Design — The SLT2 transmitter features maximum comfort with an ergonomic handle and foam wheel grip, reducing fatigue during extended bashing sessions and improving control precision.
- Adjustable Steering Rate — Easy-to-adjust steering rate allows you to customise the vehicle's handling characteristics to match your driving style and skill level, from smooth, predictable turns to responsive, aggressive steering.
- Anodised Aluminium Heatsink — The motor features an anodised aluminium heatsink that keeps the brushed motor cool during extended run times whilst adding a premium aesthetic touch to your RC basher.
- Integrated Dirt Deflectors — The clipless body mount features integrated dirt deflectors positioned behind the front wheels to keep out the worst of the elements, protecting the chassis and drivetrain from mud and debris.
- Secure Battery Mounting — Dedicated battery mounting system keeps the Spektrum Smart battery securely fastened even during the roughest terrain and most aggressive stunts, preventing battery movement or ejection.
- Integrated Cable Management — Internal wire routing and cable management holds wires safely tucked away, keeping the GRANITE GROM looking neat and tidy whilst protecting cables from damage.
- Rubber-Shielded Ball Bearings — Unlike many small scale RC vehicles, the GRANITE GROM is equipped with a full set of rubber-shielded ball bearings for extreme performance and protection from dirt and moisture.
- Indexed Motor Mount — The motor mount locks the brushed motor securely into place whilst allowing easy gear ratio changes with perfect gear mesh every time, supporting quick tuning and upgrades.
- Universal Joint Front Driveshafts — CVD front driveshafts provide smooth, bind-free steering movement during aggressive cornering and stunts, whilst dogbone rear driveshafts deliver durable power transmission.
- Geared Differentials — Twin geared differentials with standard grease allow the GRANITE GROM to lay down the power and hunt down traction across all terrains.
- dBoots® FORTRESS™ Tyres — Tough, vented dBoots FORTRESS tyres provide ultimate traction and durability, with a 125mm diameter (4.92 inches) mounted on 12mm hex wheels for compatibility with a wide range of upgrade options.
- M4 Axles and Wheel Nuts — 25% bigger than traditional small scale vehicle axles and wheel nuts, providing more secure wheel fitting and enhanced durability for serious bashing.
- 12mm Hex Wheels — The 12mm hex standard allows access to a wide range of aftermarket wheel and tyre options, enabling customisation and upgrades to suit your style.
- Spektrum SMART Battery and Charger Included — The Spektrum Smart 7.4V 1400mAh 2S LiPo battery (30C) includes integrated microchip technology and internal battery temperature monitoring to guarantee safe charging and discharging, with a hard case for additional protection.
- Spektrum S10 2S USB-C Smart Charger — The included USB-C Smart charger automatically detects battery information and delivers 1.5A fast charging with automatic cut-off, typically achieving a full charge in one hour or less when paired with a QC 2.0/3.0 18W+ power adapter.
- Full Hex Hardware — Hobby-grade hex head hardware throughout provides ease of assembly, reliability, and quality superior to competitor cross-head fasteners, with the included 2mm driver and wheel wrench fitting all adjustment and maintenance tasks.
- Factory-Finished Body with Multiple Colour Choices — The professionally factory-finished truck body comes in your choice of three brilliant, durable colour schemes—red, blue, and green—allowing you to choose your favourite or collect them all.
- Two-Year Limited Warranty — ARRMA stands behind the GRANITE GROM with a comprehensive two-year limited warranty, demonstrating confidence in the build quality and durability of this ready to run RC monster truck.
- Upgrade Parts Available — GRANITE GROM tuning and upgrade parts are available separately, including a metal axle and hex set (ARA311198) for extreme durability, oil-filled differentials (ARA311193) easily tuned with 3000cSt silicone oil, an aluminium shock set (ARA330824) with threaded collars for easy preload adjustment, and adjustable steering links (ARA340208) for fast toe-angle adjustment.
Technical Performance
The ARRMA 1/18 GRANITE GROM MEGA 380 delivers impressive performance in a compact package. Powered by a torquey MEGA 380 brushed motor with 28T pinion, it achieves a top speed of 20+ mph (32+ km/h) through a precision 4WD drivetrain. The 59-tooth metal spur gear paired with the 16-tooth pinion creates a final gear ratio of 9.22:1, delivering excellent torque and acceleration across varied terrain. The brushed motor sits in an indexed mount allowing quick gear ratio changes with perfect mesh geometry. The Spektrum 2625RX integrated 2-in-1 ESC and receiver rated at 25A provides waterproof, proportional speed control, with the IC2 connector ensuring reliable power delivery to the motor. The vehicle's 7.4V 2S LiPo battery system (1400mAh capacity) delivers sufficient run time for extended bashing sessions, whilst the Smart charger with 1.5A output achieves full charge in approximately one hour. The chassis measures 250mm in length and 165mm wheelbase, with 200mm front and rear track width, creating a stable, planted platform for hard cornering and stunts. Weighing just 800g with battery included, the GRANITE GROM maintains exceptional weight distribution across its rigid moulded composite chassis. The independent suspension features oil-filled coil-over shocks with 300 cSt silicone oil and a spring rate of 0.68 N/mm, allowing the vehicle to absorb impacts whilst maintaining traction. Geared differentials with 30-tooth crowns and 12-tooth pinions (creating a 2.5:1 internal ratio) distribute torque efficiently across the 4WD system. The enclosed drivetrain with CVD front and dogbone rear driveshafts protects internal components whilst enabling smooth power delivery. Rubber-shielded ball bearings throughout reduce friction and protect against dirt ingress. All metal drivetrain components—spur, pinion, differential gears, and servo gears—ensure durability for serious bashing. The waterproof Spektrum SX110 servo with metal gears delivers fast, precise steering response essential for technical driving and stunt work.
What's in the Box
- ARRMA GRANITE GROM 4X4 Monster Truck RTR (pre-assembled, factory-finished)
- Spektrum Waterproof SLT 2-in-1 25A ESC and Receiver (integrated unit with IC2 connector)
- ARRMA MEGA 380 28T Brushed Motor (380 size, pre-installed)
- Spektrum 2.4GHz SLT2 Transmitter (2-channel radio with throttle limiters)
- Spektrum SX110 Waterproof Metal-Geared Servo (installed, metal gears)
- Spektrum Smart 7.4V 1400mAh 2S 30C Hard Case LiPo Battery (with integrated microchip, IC2 connector)
- Spektrum S10 Smart G2 Mini 2S USB-C Charger (automatic charge detection and cut-off)
- Four AA Transmitter Batteries (for the SLT2 transmitter)
- GRANITE GROM 4X4 Monster Truck Product Manual (comprehensive assembly and operation guide)
- Combined 2mm Hex Driver and Wheel Wrench (hobby-grade maintenance and adjustment tool)
What You Need to Complete
- USB Power Adapter with QC 2.0/3.0 18W+ output (e.g. Gens Ace 65W Power Supply or equivalent) — required for optimal charging speed with the included Spektrum S10 Smart charger. Standard USB chargers may charge more slowly or not achieve full charging capacity.
Frequently Asked Questions
- Is the ARRMA GRANITE GROM MEGA 380 suitable for RC beginners? — Yes, absolutely. The GRANITE GROM is specifically designed for beginners with several features that support learning. The Spektrum SLT2 transmitter includes 50% and 75% throttle limiters that allow new drivers to build control skills safely by matching the vehicle's speed to their experience level. The clipless body mount makes maintenance and adjustment easy for users of all ages, and the waterproof electronics enable relaxed, carefree bashing without worry. The 1/18 scale size makes it less intimidating than larger RC monster trucks whilst still delivering genuine ARRMA durability and performance.
- What battery does the GRANITE GROM MEGA 380 use and how long does it take to charge? — The GRANITE GROM comes with a Spektrum Smart 7.4V 1400mAh 2S LiPo battery featuring integrated smart microchip technology and internal temperature monitoring. The included Spektrum S10 Smart G2 Mini 2S USB-C charger delivers 1.5A charging current, achieving a complete charge in approximately one hour when paired with a QC 2.0/3.0 18W+ USB power adapter. The Smart technology automatically detects battery parameters and applies safe, accurate charging profiles. The battery features IC2 connectors for reliable power delivery and comes in a protective hard case.
- What is the top speed of the 1/18 GRANITE GROM monster truck? — The ARRMA GRANITE GROM MEGA 380 achieves a top speed of 20+ mph (32+ km/h). This speed is achieved through the 28T brushed motor, 59-tooth spur gear, 16-tooth pinion, and 9.22:1 final gear ratio driving the 4WD transmission. The Spektrum SLT2 transmitter's 50% and 75% throttle limiters allow beginners to reduce maximum speed whilst learning, with full speed available once skills develop.
- Is this RC truck waterproof and can I use it in wet conditions? — Yes, the GRANITE GROM features waterproof electronics throughout. Both the Spektrum 2-in-1 ESC/receiver and the Spektrum SX110 servo are waterproof-rated, enabling confident operation in wet grass, muddy terrain, water crossings, and rain. However, for specific waterproof operating specifications, you should refer to the product instruction manuals included with the vehicle.
- What makes the GRANITE GROM different from other small-scale RC monster trucks? — The GRANITE GROM stands out through genuine ARRMA engineering with no compromises despite its small 1/18 scale size. Key differentiators include the innovative clipless body mount system for tool-free removal, full metal gears throughout (spur, pinion, servo, differentials) for durability, rubber-shielded ball bearings that protect against dirt ingress, waterproof electronics, oil-filled telescopic shocks, and an enclosed drivetrain with integrated dirt deflectors. The included Spektrum Smart battery and charger system with automatic detection and temperature monitoring provides peace-of-mind charging. Additionally, the 12mm hex wheels enable access to extensive aftermarket options, and dedicated upgrade parts are available for tuning.
- How often will I need to charge the battery and what runtime can I expect? — The Spektrum 7.4V 1400mAh battery provides sufficient capacity for extended bashing sessions, though exact runtime depends on driving intensity, terrain, and throttle usage. Hard acceleration and aggressive driving reduce runtime, whilst controlled speed increases it. The battery charges fully in approximately one hour with the included Smart charger and a suitable power adapter, making it practical to charge during breaks or overnight.
- What upgrade parts are available for the GRANITE GROM? — ARRMA offers several upgrade options to enhance performance and durability. The metal axle and hex set (ARA311198) increases strength for extreme bashing. The assembled oil-filled differential set (ARA311193) allows tuning with 3000cSt silicone oil for customised traction characteristics. The aluminium shock set (ARA330824) provides threaded collars for easy preload adjustment and refined suspension tuning. Adjustable steering links (ARA340208) enable quick toe-angle adjustment for handling preferences. All upgrade parts are designed specifically for the GRANITE GROM and fit without modification.
- Does the GRANITE GROM come fully assembled and ready to run? — Yes, the GRANITE GROM is a true ready-to-run (RTR) vehicle. It arrives fully pre-assembled with factory-finished body, installed motor, servo, ESC/receiver unit, and suspension. You simply charge the included battery, insert four AA batteries into the transmitter, and you're ready to bash—no soldering, no complex assembly, no technical knowledge required.
- How small is the GRANITE GROM compared to other ARRMA models? — At 1/18 scale, the GRANITE GROM measures 250mm in length and 118mm in height, making it nearly half the size of the 1/10 scale GRANITE MEGA. For reference, the front width is 200mm (7.87 inches). This compact size makes it genuinely portable—small enough to take on holiday, keep in your car, or store in a desk drawer—whilst maintaining full-sized ARRMA durability and performance characteristics.
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 ARRMA 1/18 GRANITE GROM MEGA 4X4 MT with Battery & Charger Red C-ARA2102T2 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.
