How to Make an RC Car Faster: The Upgrades We Recommend
In this article (4)
Three things make an electric RC car faster: more voltage, taller gearing and a brushless motor. Do the cheap, low-risk jobs first, and check what your speed controller can take before you buy anything. The second half of this page is a real conversion we did on a brushed 2WD truck. It did 36 km/h out of the box and 63 km/h afterwards, and the steps and photos are below.
Check the limits before you upgrade anything
Speed controller (ESC) voltage. The manual states the most cells it will take, for example 2S or 3S LiPo. A battery over that limit can destroy it.
Low-voltage cut-off. If you're moving to LiPo, the ESC must have a LiPo cut-off and it must be switched on. Running a LiPo flat ruins it.
Charger. You cannot charge a LiPo on a NiMH charger. Trying is dangerous. Use a LiPo charger.
Drivetrain. Plastic gears and driveshafts that cope with a brushed motor can strip under brushless power. Expect to replace more parts once the car is faster.
Heat. After any change, run the car for two or three minutes and feel the motor. If it's too hot to keep a finger on, back the change off.
The upgrades, cheapest first
1. Make it roll freely (free)
Clean the dirt out of the axles and gears, and check that each wheel spins freely. A wheel nut done up too tight is drag you can fix for nothing.
2. Tyres for the surface
Power you can't put down is wasted. Soft knobbly tyres squirm on bitumen and concrete; on-road wheels grip better there. At high speed an ordinary tyre balloons outwards and the car gets unstable. Belted tyres have a woven band inside that stops it. This is the upgrade that also helps handling.
3. Ball bearings in place of bushings
Many entry-level cars have plain plastic or brass bushings where the axles turn. Ball bearings take load off the drivetrain. Measure the old bushing or look your model up in the Part Finder, because sizes vary. The Atrek 5x10x4mm set is one common size (Atrek is our own brand).
4. Gearing
A pinion with more teeth, or a spur with fewer, raises top speed and costs acceleration. The motor isn't any more powerful, so it works harder and runs hotter. Go up one or two teeth at a time and check the temperature after two or three minutes before you run a whole battery. If the car shuts down from heat, go back down.
Two things must match before a pinion will fit: its pitch has to be the same as the spur's, and its bore has to suit the motor shaft, which is commonly 3.17 mm or 5 mm. Gear ratios explained covers the sums, and how to set a gear mesh covers fitting.
5. More voltage
A motor's Kv is the rpm it turns per volt with no load. So a 3300Kv motor turns about 24,400 rpm on a 2S LiPo (7.4 V) and about 36,600 rpm on 3S (11.1 V). That's half as much motor speed again, and it's only on offer if the ESC is rated for 3S. In the words of our 2023 build: too much voltage and "you'll let the magic smoke out of your electronics... and I still haven't worked out how to put the smoke back in".
6. Brushless motor and ESC
If the car has a brushed motor, this is the change that transforms it. Buy the motor and ESC as a combo so they're matched. The Hobbywing Quicrun 10BL120 combo pairs a waterproof 120A speed controller, rated to 4S, with a 3652-size 4000kV motor, the same motor size and Kv we used in the build below. Not sure what you have now? Brushed motors have two wires. Brushless have three.
Our build: a brushed truck from 36 to 63 km/h
In 2023 Aaron, who writes most of this blog, converted a brushed HSP Viper, a 1/10 scale 2WD stadium truck that came with a brushed motor and a 6-cell NiMH battery. Out of the box it did 36 km/h. You can watch the build or follow it here.
He skipped steps 4 and 5 on their own. A LiPo or a 7-cell NiMH would "wake the car up a bit" but, on the stock brushed motor and ESC, wouldn't really change the top speed and would shorten their life. Taller gearing would add a couple of km/h, and the car would take longer to get there. So the truck got a Hobbywing Max10 60A combo with a 3652-size 4000kv sensorless motor, and a 5000mAh 2S LiPo.
Three things from that build are worth copying when you choose parts:
Use the factory brushless version as your baseline. If the maker sells your car with a brushless motor, note its size and Kv. This truck's brushless version used a 3300kv motor of the same size, so a 4000kv would be faster with less torque. For the same size of motor, higher Kv is faster and lower Kv has more torque. Go too high and the motor can't move the car.
Check the motor shaft. 3.17 mm and 5 mm are the two common sizes, and your pinion has to fit.
Give the ESC headroom. The amp rating is the current it can sustain. Faster motors draw more, hardest at launch.
What you need
The brushless motor and ESC.
A LiPo battery the ESC is rated for, and a LiPo charger.
Hex drivers for the motor and pinion. On this truck, 1.5 mm and 2.5 mm.
A microfibre cloth and methylated spirits, to clean the chassis where the ESC will stick.
Zip ties for the wiring.
The swap, step by step
Disconnect the battery. Take a photo of how everything is plugged in.
Unplug the old ESC from the receiver (channel 2) and from the motor, and lift it out. This one was held by double-sided tape.
Remove the gear cover (two screws on this truck) and unbolt the motor (two more).
Move the pinion from the old motor to the new one.
Bolt the new motor in. If the mesh is adjustable, set it as you tighten the screws, and check the pinion lines up with the spur.
Clean both surfaces and stick the new ESC down where it fits best.
Plug in the three motor wires, usually marked A, B and C. Plug the ESC into channel 2 of the receiver.
Calibrate the ESC to your transmitter, with the throttle trim at neutral.
Test gently. If the car won't go forward, flip the channel 2 reverse switch on the radio. If it's faster in reverse than forwards, swap any two motor wires.
Put the car on a box with the wheels off the ground and test the fail safe by switching the remote off first. Normally the remote goes on first and off last.
The result, in Aaron's words: "Our viper went from 36kmh out the box to a new top speed of 63km/h!" And the cost: "likely more breakages and worn out parts".
If you'd rather buy speed than build it, see the fastest RC cars you can buy.
Frequently Asked Questions
How do you make an RC car faster without changing the motor?
Fit a pinion gear with one or two more teeth, or a battery with a higher voltage if the speed controller is rated for it. Both raise top speed and both make the motor run hotter, so check its temperature after two or three minutes. On a brushed motor the gain is small: in our own build we expected only a couple of km/h from either.
How do you make an RC car faster for free?
Clean the dirt out of the axles and gears, make sure every wheel spins freely, and check that the wheel nuts are not done up too tight. That removes drag without buying anything. It will not add much speed, but it is the right first step before spending money.
Will a higher voltage battery burn out my RC car's motor?
It can. A battery with more cells than the speed controller is rated for will destroy the controller, and extra voltage on tall gearing overheats the motor. Check the maximum cell count in the speed controller's manual first, and feel the motor after two or three minutes of running.
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