The SCX10 II UMG10 Kit is a 1/10 four-wheel-drive crawler kit from Axial, sold without a motor, speed control, servo or radio.
The 15T pinion and 56T spur, through a 10.83:1 internal ratio, give a 40.44:1 final drive on 117 mm tires, slow enough for careful crawling. The kit is 455 mm long on a 288 mm wheelbase. Pinions are 32P, so spares in other sizes are easy to find. Choose a motor that suits slow, steady crawling.
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.
Crawlers are built for slow, controlled climbing over rocks: very low gearing, flexible suspension and locked axles.
Drive
All four wheels are driven. That gives more grip under power, especially on loose ground.
The cost is more parts to maintain.
A crawler needs every wheel pulling to climb.
Power
Sold without a motor, so you choose the motor, ESC and battery yourself.
Rows that depend on the motor say so.
Build
A kit you build yourself from parts.
Most kits come without motor, ESC, servo, radio and battery, and many without tires or a painted body.
The manual lists what to add.
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 455 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
Crawler
Drive
4WD
Power
Motor not included
Build
Kit
Scale
1/10
Part number
AXI90075
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 6.7%.
Crawlers run small pinions for slow, precise wheel speed on climbs; a bigger one is quicker on the trail but harder to control on rocks.
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, transfer case and axle gears.
That chain is why a crawler's figure is much higher than other classes'.
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 3.733:1.
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 crawlers & trail trucks in the catalog, the middle half run between 27.1:1 and 44.0:1 on stock gearing; this one is 40.4:1.
Crawlers run far higher ratios than other classes, so the truck can creep and hold on a climb.
Pinion
15TStock
Stock
Spur
56TStock
Stock
Transmission & axle
10.83:1Derived
Derived
Spur ÷ pinion
3.733:1Calculated
Calculated
Final drive
40.44:1Stock
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.
Crawler wheels are named by rim size, such as 1.9 or 2.2 inches; that is the wheel, not this tire diameter.
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 9.1 mm.
Tire diameter
117mmStock
Stock
Rollout
9.1mm per motor turnCalculated
Calculated
Power
Motor
Motor KV is the RPM a motor turns per volt with no load.
This vehicle comes without a motor, so there is no stock KV; it depends on the one you fit.
Motor shaft
The diameter of the motor's output shaft, which a pinion's bore must match.
This vehicle comes without a motor, so it depends on the one you fit.
Battery
The highest LiPo cell count the maker rates the electronics for.
This vehicle comes without electronics, so it depends on the ESC and motor you fit.
Battery space
The biggest pack that fits the tray, as the maker states it: length and width, and height where given.
Compare it with the pack's case size, not its capacity.
Allow room for the leads.
Motor
Not applicable
Motor shaft
Not applicable
Battery
Not applicable
Battery space
147 × 32 mmmax pack, length × widthStock
Stock
Performance
Theoretical top speed
It needs a motor KV, and this vehicle comes without a motor. Fit one and the calculator works it out from the motor's KV and the gearing.
Theoretical top speed
Not applicable
Size & weight
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.
On a crawler it also decides how well the truck clears a ledge without the chassis catching.
Length
455 mm17.9 inStock
Stock
Width
230 mm9.1 inStock
Stock
Height
245 mm9.6 inStock
Stock
Wheelbase
288 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 Axial SCX10 II UMG10 Kit: fitted, and optional gearing supplied in the box
Component
Teeth
Pitch
Bore
Fitted at the factory
Pinion
15T
32P
Not published
Spur
56T
32P
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.
A kit sold without a motor, ESC, servo or radio, so there is no Kv or cell rating to publish.
Horizon's page prints Pinion 15T, Spur Gear 56T, Gear Pitch 32-Pitch and Final Drive Ratio 40.44, and its feature list says the kit comes with the 56T spur gear and the 15T pinion.
The 10.83 ratio after the spur is worked out from the printed total (40.44 x 15 / 56).
The page prints the tire's Outer Diameter as 4.6 in (117mm).
Horizon also prints a range of 33.69 - 54.15 for other spur and pinion pairs.
No gear part numbers are published on the page, so only the 32-pitch is recorded.
Big Squid RC reported the kit in April 2019.
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.
