Cars and crawlers, taken apart.
Sixty years of radio cars, every part of a short-course truck, and benches you can drive yourself. By the SunTzu RC crew, about 15 minutes.
assembled · 10 assemblies · 85 parts
A radio-control car is the easiest way into the hobby and one of the deepest. There is no airspace to learn and nothing to fall out of the sky. But under the body of a short-course truck sit the same ideas as in a real one: a differential, a spring and a damper at every corner, and gearing that trades speed for pull.
We'll start with where it came from, take those three apart on the bench, then go part by part through what you'll actually buy.
Where it started
Scroll through the milestones. Each one links to where we checked it.
1960s
The first radio-controlled model cars
Radio-controlled model cars first appeared in Europe in the mid-1960s. The Italian toy maker El-Gi (Elettronica Giocattoli) of Reggio Emilia sold 1:12 scale Ferraris.
1967
ROAR is organised
ROAR, Remotely Operated Auto Racers, the US non-profit that runs RC car racing, was organised. It is North America's member of the world federation and the only body that can send drivers to its world championships.
1976
Tamiya's first RC car, a Porsche 934
In November 1976 Tamiya released its first RC car, a 1/12 scale Porsche 934 Turbo with spring suspension and a rear differential. Buyers supplied their own radio and servos.
1979
IFMAR becomes the world federation
The International Federation of Model Auto Racing was officially inaugurated to run world championships for RC cars. Britain's Ted Longshaw was its first president.
1984
The Hornet helps start the buggy boom
Tamiya's Hornet, a two-wheel-drive off-road buggy with a 540 motor and oil-filled rear dampers, helped launch a worldwide boom in RC buggies.
1984
Team Associated launches the RC10
The RC10 electric off-road buggy had an anodised aluminium tub chassis, oil-filled shocks and an adjustable ball differential. In 1985 Jay Halsey drove one to the IFMAR 1:10 electric off-road two-wheel-drive world title.
2002
Brushless motors reach RC cars
Novak Electronics released the Super Sport Brushless System, which it describes as the first sensored brushless motor and speed control for RC cars.
2004
2.4 GHz radios arrive
Spektrum showed its 2.4 GHz DSM radio technology at the 2004 iHobby Expo. It was designed first for cars and trucks, and its first all-in-one transmitter, the DX3, followed in May 2005.
2007
The AX10 makes crawling a category
Axial released the AX10, which it calls the first purpose-built RC rock crawler. Before it, hobbyists built crawlers from the parts of several kits. Axial later followed it with the SCX10 scale trail truck.
2008
ROAR allows LiPo batteries
ROAR approved lithium-polymer packs for sanctioned racing, as long as they come in a hard case and pass safety tests, the most important being an overcharge test.
2008
The Slash starts short-course racing
Traxxas released the Slash, a replica of full-size short-course off-road race trucks. Racers soon formed classes for it, and other makers followed with short-course trucks of their own.
2026
Tamiya marks 50 years of RC cars
Tamiya released a 1/10 scale Porsche 934 (1976) 50th Anniversary kit in Japan in May 2026, honouring its first RC car.
Why the wheels turn at different speeds
In a corner the outside wheels travel a bigger circle than the inside ones in the same time, so they have to turn faster. Fix both rear wheels to one shaft and one of them has to skid. A differential fixes that. The drive turns a ring gear on the diff's case; inside, small bevel gears called spiders mesh with a side gear on each axle. Going straight, the whole lot turns as one. In a corner the spiders turn on their pin, and each wheel follows its own path while the case runs at the average of the two.
Steer the bench below, or tab to it and use the arrow keys.
straight · both wheels 965 rpm · spiders still
Drag across the axle to steer, or use ← →
At full lock on Fig 2 the inside wheel slows to 803 rpm and the outside one speeds up to 1126 rpm, while the ring gear keeps turning at 965. Nothing skids.
The catch is the slipping wheel. An open diff splits the torque equally, so when one wheel loses grip, the other gets no more than the slipping one can take: lift a wheel and it spins while the truck sits still. A limited-slip diff resists that; the 1984 RC10 had an adjustable ball diff. Rock crawlers go further and lock their diffs, so both wheels on an axle always turn together. It climbs far better and turns worse, because in a corner one tyre has to scrub.
Every part, and what it does
A two-wheel-drive short-course truck with its body off, from the bumpers in. Scroll and watch the part light up on the truck.
Chassis
Chassis
The tub that everything else bolts to, with a bumper at each end.
538 mm long
A short-course truck is long and wide for its class: the Team Associated Pro2 SC10 is 538 mm long and 282 mm wide on a 322 mm wheelbase, and weighs 1928 g ready to run.
Body shell
A replica of a full-size short-course race truck, held on by clips.
Off in seconds
It keeps dirt off the electronics and, on a short-course truck, covers the tyres like the real thing. Take it off first for anything you do on the bench.
Wheels and tyres
Grip, mostly. On dirt, the tyre matters more than almost anything else you can change.
About 110 mm
Makers rarely publish short-course tyre sizes; a typical one, the Pro-Line Trencher X, is 110 mm tall and 47 mm wide. Each wheel sits on a hex hub and is held by one nut.
Suspension arms
Let each wheel move up and down on its own while the chassis stays level.
Four corners
Each arm pivots on the chassis at one end and carries a hub at the other. Fig 3 shows what happens when one of them drops over a bump.
Shocks
A spring to hold the truck up, and a piston in oil to stop it bouncing.
350 cSt stock
The Pro2 SC10 ships with 30wt oil front and rear, which is 350 cSt in Team Associated's oil. Fig 3 lets you try thinner and thicker.
Steering
A servo turns the front wheels through a servo saver and two links.
Servo saver
The saver is a spring-loaded arm on the servo. When a front wheel hits something hard, it gives instead of stripping the servo's gears.
Brushless motor
Turns battery power into spin, with no brushes to wear out.
3300 kV
kV is rpm per volt with nothing attached: 3300 kV on a 7.4 V pack is about 24,400 rpm unloaded. Under load it turns slower, which is why top-speed sums are theoretical.
Pinion and spur
The first step down: a small gear on the motor drives a big one on the transmission.
18T and 87T
Change the pinion and you change the truck's gearing. Fig 4 shows what one tooth more or less does to speed.
Transmission and diff
Gears the spur down again and splits the drive between the rear wheels.
2.6:1 inside
Inside is the differential that lets the rear wheels turn at different speeds in a corner. Fig 2 takes it apart.
Driveshafts
Carry the drive from the transmission out to each rear hub while the suspension moves.
Two-wheel drive
Many short-course trucks come in two- and four-wheel-drive versions. Four-wheel drive adds shafts and a diff at the front, and often one in the middle.
Speed controller (ESC)
Turns your throttle into motor power, forwards, braking and reverse.
LiPo cutoff
Modern ones have a low-voltage cutoff that eases off the motor before a LiPo pack drops too low. Make sure it's switched on if you run LiPo.
Receiver
Listens to your transmitter on 2.4 GHz and sends the servo and ESC their signals.
2.4 GHz
Some ready-to-run cars now have a gyro built into the receiver that helps catch a slide, a long way from the fixed-frequency radios of the eighties.
LiPo battery
Stores the energy, down the middle of the chassis where its weight does least harm.
2S = 7.4 V
Racing rules have required hard-case LiPo packs since ROAR first allowed them. Balance charge, never leave a pack charging unattended, and store it around 3.8 V per cell.
Springs hold it up, oil calms it down
A spring alone would let the truck land a jump and keep bouncing. The other half of a shock absorber stops that: a piston on the shaft is pushed through oil, and the oil has to squeeze through small holes in it. The harder you push, the harder it pushes back.
The bench below drops one corner of a truck from 20 mm, the way you'd drop it on the bench to check it. Change the oil and watch the chart.
350 cSt (30wt) · bounces 1.9 mm past · settles 0.18 s
Drag across the rig to change the oil, or use ← →
With the stock oil the corner dips 1.9 mm past where it settles and is still within a millimetre after 0.18 s. Thin oil lets it pogo; thick oil stops the bounce but makes the wheel slow to come back down, and on a rough track it can't keep up with the next bump.
Compare oils in centistokes. Shock oil is sold by weight, but one brand's 30wt isn't another's; centistokes (cSt) are the same everywhere. Team Associated's oils run from 25wt (275 cSt) to 50wt (650 cSt). The piston matters as much as the oil: bigger or more holes make a shock softer, fewer or smaller ones make it firmer.
Gearing for speed
A motor spins far faster than the wheels can, so gears bring it down twice: a small pinion on the motor drives a big spur gear, and the transmission reduces again inside. Multiply the two and you get the final drive ratio. On the Pro2 SC10 that's 87 ÷ 18 × 2.6 = 12.57:1.
18T pinion · 12.57:1 · 27.5 mm a turn · 40 km/h
Drag across the bench to change the pinion, or use ← →
Divide the tyre's circumference by the final drive and you get rollout: how far the truck moves for one turn of the motor, 27.5 mm with the stock pinion. More teeth on the pinion mean more rollout and more speed, and more work for the motor on every metre.
Those speeds are a ceiling, not a promise. A motor's kV is its rpm per volt with nothing attached, so the truck on the ground is slower than the sum. Put a 3S pack in and the voltage goes up by half; the manual then asks for a 17-tooth pinion, which on paper gives about 57 km/h and keeps the motor's load in check.
Crawlers: the slow end
A rock crawler turns everything above around. The Axial SCX10 III Base Camp has a brushed 35-turn motor, a 14-tooth pinion on a 52-tooth spur and a final drive of 45.6:1, about 3.6 times the reduction of the short-course truck, on 119 mm tyres with both diffs locked. It is built to creep up a rock face at walking pace and stop exactly where you let go.
Crawling became its own category in 2007, when Axial released the AX10, which it calls the first purpose-built RC rock crawler. Before that, people built crawlers from the parts of several kits.
Then and now
A late-eighties Team Associated RC10 kit and the RB10 you can buy ready to run today do the same job. Almost everything else changed.
| Aspect | 1980s | Today |
|---|---|---|
| Motor | A brushed motor | A 3300 kV brushless motor |
| Battery | A six-cell NiCd pack | A 2S or 3S LiPo |
| Radio | A fixed frequency: two cars couldn't share a channel | 2.4 GHz, with a gyro in the receiver |
| Chassis | Gold-anodised aluminium tub, ball diff, oil shocks | Moulded composite chassis, sealed gear diff, 12 mm big-bore shocks |
| Speed control | A resistor and wiper speed control | A brushless ESC with a LiPo low-voltage cutoff |
Sources: the RC10's history, the RB10 and the switch to 2.4 GHz.
Driving one in South Florida
There's no FAA paperwork for a car. You need somewhere to drive it. Coral Springs RC Track, behind petrillo park, coral springs, runs ROAR-sanctioned off-road and on-road racing, and West Delray Regional Park in Delray Beach has an RC car track alongside its flying field. Parks and parking lots have their own rules, so ask before you bash.
Or let us walk you through it. We'll help pick the truck, set its gearing and shocks on the bench like Figs 3 and 4, and come to the track for the first run.