1/10 scale · 2WD short course chassis kit · 320301
Also sold as the XRAY SCX'25
XRAY's SCX'23 is a two-wheel-drive 1/10 short course truck kit, built by you and sold without motor, electronics or tires.
The 78T spur works through a 2.65:1 reduction in the three-gear transmission, so the pinion you fit sets the final drive. It uses 12 mm hexes. The gear diff comes filled with 5K oil, and the shocks with 650 cSt front and 500 cSt rear. Short course tracks change grip through a day, so move the diff oil in small steps and note each change.
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.
Short course trucks copy full-size desert race trucks, with bodies that cover the wheels so they can bump each other without tangling.
Drive
Only one axle is driven, the rear on almost every 2WD RC car.
It is lighter and simpler, and it takes more throttle control on loose ground.
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.
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
Short course
Drive
2WD
Power
Motor not included
Build
Kit
Scale
1/10
Part number
320301
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 a chassis sold as kits, each kit brings its own.
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.
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.
Diff oil, rear
Silicone oil sealed inside the differential. A diff lets the wheels on one axle turn at different speeds in a corner; thicker oil makes it act more like a solid axle.
At the rear, thicker oil puts power down more evenly on loose or slippery ground; thinner oil lets the car rotate more easily through a corner.
It is graded in cSt (centistokes), a measure of thickness that means the same across brands. K means thousands, so 5K is 5,000 cSt.
Pinion
Not applicable
Spur
78TStock
Stock
Transmission & axle
2.65:1Derived
Derived
Final drive
Not applicable
Diff oil, rear
5KStock
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.
Race tires wear down over a day, and a smaller tire gears the car shorter.
Wheel hex
The hex on the axle that the wheel locks onto and is driven by. A wheel must match the hex size to fit.
12 mm is the common size on 1/10 cars, so most 1/10 wheels fit; offset and width still vary.
The wheel nut is a separate size, so check its thread too before buying nuts.
Tire diameter
Not applicable
Wheel hex
12 mmStock
Stock
Suspension
Shock oil, front
The oil in the shocks slows how fast the suspension moves. Thicker oil settles the car more slowly and resists bottoming out; thinner oil lets the wheels follow bumps.
At the front it mostly shapes the steering: thicker oil makes the car turn in more calmly and dive less under braking; thinner oil turns in sharper and keeps the front tires on the ground over bumps.
Racers go thicker for big, smooth jumps and thinner for rough, choppy tracks.
It is graded in cSt (centistokes), a measure of thickness that is the same across brands.
Shock oil, rear
The rear shocks mostly shape grip under power and how the car lands.
Thicker oil at the rear holds the back up on landings and keeps it steadier on the throttle; thinner oil lets it squat and follow rough or loose ground for more grip.
This car runs thicker oil at the front (650 cSt) than the rear (500 cSt). The front reacts more slowly, which steadies the steering, while the rear follows the ground more freely for grip under power.
Shock oil, front
650 cStStock
Stock
Shock oil, rear
500 cStStock
Stock
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.
Motor
Not applicable
Motor shaft
Not applicable
Battery
Not applicable
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
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.
Gearing parts
Pinion and spur parts for the XRAY SCX'23: fitted, and optional gearing supplied in the box
Component
Teeth
Pitch
Bore
Part number
Fitted at the factory
Spur
78T
Not recorded
Not applicable
365878
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.
2WD short course truck kit; XRAY's own product list now names kit 320301 the SCX'25, while its features page and manual call it the SCX'23.
The manual marks the 78T/48 slipper spur (#365878) as included, and the features page names 78T as standard with 75T and 81T as options.
The 3-gear gearbox runs a 20T top shaft through a 38T idler to the 53T gear diff case (#324954), so the ratio after the spur is worked out as 53/20 = 2.65, the constant XRAY prints for the same 20T and 53T gears on the XB2.
Motor, pinion, speed controller, tires and inserts are on the list of items to buy, so the tire size is left blank.
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.
