The Granite 4X4 MEGA 550 is a ready-to-run 1/10 four-wheel-drive monster truck from Arrma, with a MEGA 12T brushed 550 motor and a MEGA waterproof ESC.
A 14T pinion on a 91T spur gives an 18.72:1 final drive, which keeps the brushed motor's load down on 127 mm tires. The truck weighs 2.9 kg, is 429 mm long and takes up to a 2S pack through an IC3 plug. Pinions are 48P, so spares in other sizes are easy to find. If the motor runs hot, check the gearing before the batteries.
The kind of vehicle the maker sells it as. It sets what the car is built to do and which cars it is fair to compare it with.
Monster trucks have tall tires and long suspension travel, built for jumping and rough ground rather than a race track.
Drive
All four wheels are driven. That gives more grip under power, especially on loose ground.
The cost is more parts to maintain.
Power
A brushed motor carries current through carbon brushes that rub on the commutator.
It is cheaper and smooth at low speed.
The brushes wear and the motor loses power over time.
Build
Ready to run: built at the factory with the electronics installed.
Some come without a battery or charger; the maker's box contents say which.
Scale
The maker's nominal size compared with a full-size vehicle. It works more as a class label than a measurement.
A 1/10 monster truck is far bigger than a 1/10 touring car, so compare length and weight for real size.
This one is 429 mm long.
Part number
The maker's product number for this exact version.
A V2, a new color, or a kit instead of an RTR usually has a different number, and parts can differ between them.
Check it against your box or receipt before ordering parts.
Class
Monster truck
Drive
4WD
Power
Brushed
Build
Ready to run
Scale
1/10
Part number
ARA102714
Drivetrain
Pinion
The small gear on the motor shaft. Fewer teeth gear the car shorter: quicker acceleration, lower top speed and a cooler motor. More teeth do the opposite.
On this car one tooth changes the gearing by about 7.1%.
A bigger pinion loads the motor and ESC harder, so check the maker's gearing chart and feel the motor temperature after a run.
Spur
The large gear the pinion drives. A bigger spur with the same pinion gears the car shorter.
Pinion and spur must have the same pitch, or tooth size, to mesh.
The Gearing parts table below shows this car's pitch and part numbers.
Transmission & axle
Every reduction after the spur, multiplied together: transmission, differentials and axle gears.
It is fixed by the design; the gearing you change is the pinion and spur.
This one is worked out from the tooth counts the maker publishes.
Spur ÷ pinion
Spur teeth divided by pinion teeth: the part of the gearing that a pinion or spur swap changes.
Here it is 6.500:1.
Final drive
How many times the motor turns for one turn of the wheels. A higher number is shorter gearing: more acceleration and pulling power, less top speed.
Among 1/10 monster trucks in the catalog, the middle half run between 11.4:1 and 15.1:1 on stock gearing; this one is 18.7:1, shorter than most.
Pinion
14TStock
Stock
Spur
91TStock
Stock
Transmission & axle
2.88:1Derived
Derived
Spur ÷ pinion
6.500:1Calculated
Calculated
Final drive
18.72:1Stock
Stock
Wheels & tires
Tire diameter
The outside diameter of the mounted tire, tread to tread. A taller tire covers more ground each turn, which gears the car taller.
At high speed tires can balloon and grow, so the real gearing gets taller as the car goes faster.
Rollout
How far the car moves for one turn of the motor: tire circumference divided by final drive.
It lets you compare gearing across different tire sizes; more rollout is taller gearing.
Here it is 21.3 mm.
Tire diameter
127mmStock
Stock
Rollout
21.3mm per motor turnCalculated
Calculated
Power
Motor
Brushed motors are rated by can size and turns rather than KV, so there is no KV to show.
Battery
The highest LiPo cell count the maker rates the electronics for. Each cell is 3.7 V nominal and 4.2 V fully charged.
2S is 7.4 V nominal and 8.4 V off the charger.
Running more cells than this risks the ESC and motor.
Many cars also run on fewer cells, only slower.
Stock motor
The motor fitted at the factory, as the maker names it.
Brushed motors are often named by can size, such as 540 or 550, and by turns: fewer turns is faster.
Stock ESC
The electronic speed control. It feeds power from the battery to the motor as you work the throttle, and usually powers the receiver and servo too.
An amp figure in its name is normally the maker's continuous rating.
A brushed ESC cannot run a brushless motor.
Set its low-voltage cutoff for LiPo, so a pack is not run flat.
Battery connector
The plug on the battery lead. Your battery needs the same plug.
An adapter works, but it adds resistance and another joint that can work loose.
Spektrum's IC3 and IC5 plugs also accept EC3 and EC5 plugs, and let Spektrum Smart chargers read Smart packs.
Motor
Not applicable
Battery
Up to 2SLiPoStock
Stock
Stock motor
MEGA 12T Brushed 550 motorStock
Stock
Stock ESC
MEGA waterproof ESCStock
Stock
Battery connector
IC3Stock
Stock
Performance
Theoretical top speed
A brushed motor has no KV rating, so no theoretical top speed is worked out. Compare gearing by rollout instead.
Theoretical top speed
Not applicable
Size & weight
Weight
The vehicle's weight as the maker states it.
The maker does not say whether it includes a battery.
More weight takes more power to accelerate and lands harder on the parts; it changes top speed very little.
Length
Overall length as the maker states it, usually with the body fitted.
Useful for comparing real size, since scale labels are loose.
Width
Overall width as the maker states it, usually with the body fitted.
A wider car is more stable in corners and harder to roll over.
Height
Overall height as the maker states it, usually with the body fitted.
Useful when checking it fits a shelf, a bag or a car trunk.
Wheelbase
The distance between the front and rear axle centers. A longer wheelbase is steadier at speed and over bumps; a shorter one turns more tightly.
Weight
2.9 kg (6.4 lb)Stock
Stock
Length
429 mm16.9 inStock
Stock
Width
342 mm13.5 inStock
Stock
Height
196 mm7.7 inStock
Stock
Wheelbase
287 mm11.3 inStock
Stock
How to read these figures
Stock is as the vehicle ships.
Calculated is worked from the stock figures on this page rather than stored beside them, so the two cannot drift apart.
Derived is worked out from gear tooth counts the maker publishes rather than printed as a ratio; the notes below say how.
Not applicable means the vehicle does not come with it, like the motor on a roller or the tires on a race kit, or does not have one, like a KV rating on a brushed motor.
Pinion and spur dimensions for the Arrma Granite 4X4 MEGA 550: fitted, and optional gearing supplied in the box
Component
Teeth
Pitch
Bore
Fitted at the factory
Pinion
14T
48P
Not published
Spur
91T
48P
Not applicable
About teeth, pitch and bore
Tooth counts are the ones in the specifications above.
Pitch is given as metric module (Mod 1, Mod 0.8) or diametral pitch (32P, 48P). They are different standards and are not interchangeable, even where the numbers look close.
Bore is the pinion’s hole, listed separately from the motor shaft.
Horizon's page for the original Granite 4X4 MEGA 550 prints Pinion 14T, Spur Gear 91T, Gear Pitch 48-Pitch and Final Drive Ratio 18.72, but no internal ratio.
The 2.88 internal ratio shown here is worked out from the printed total (18.72 x 14 / 91), and it matches the 2.88 that Horizon prints for the Typhon 4X4 MEGA 550 with the same gears.
The tire is a dBoots Fortress, and the page prints its Outer Diameter as 5 in (127mm).
The manual's ESC specification gives the input as 6 to 7 cell NiMH or 2S LiPo, so 2 cells is the LiPo limit.
The motor is a brushed MEGA 12T 550, so there is no Kv figure.
Horizon lists the 14T 48DP pinion ARAC7777 as a standard part of this SKU; the 91T spur's part number is not named for it.
The Granite 4X4 MEGA 550 V3 is a separate listing that prints an 18.5 final drive and a 128 mm tire.
Arrma's 30 mph claim assumes optional gearing, so it is not used.
Sources
Every figure on this page traces to one of these; where they disagreed, the note above says which was used and why. Links open in a new tab.
