RC Brushless Motor Size Chart: Choose The Best

RC Brushless Motor Size Chart

The brushless motor is one of the three major power accessories of RC electric vehicles. With a suitable motor, you can get the best running effect. The following contents will help you to understand the motor easily.

RC Brushless Motor Size Chart

The size of the brushless motor is indicated by four digits, the first two digits indicate the diameter of the motor housing, and the last two digits indicate the length. For example, “3660” means 36mm in diameter and 60mm in length.

Different size motors are used in different cars. Common motor sizes on the market are as follows:

Size Diameter Length Application
2030 20mm 30mm 1/16 or 1/18 scale on-road, off-road, Monster truck, etc
2838 28mm 38mm
3650 36mm 50mm 1/10 scale on-road and drift cars, 1/10 scale off-road vehicles
3656 36mm 56mm 1/10 scale short course truck, 1/10 scale Monster truck, etc
3660 36mm 60mm
3674 36mm 74mm
4068 40mm 68mm 1/8 scale RC cars all use these common motor sizes
4074 40mm 74mm
4268 42mm 68mm
4274 42mm 74mm
5874 58mm 74mm 1/5 scale car

The size of a brushed motor is represented by a three-digit number, for example:

380 (brush) ≈ 2838 (brushless)
540 (brush) ≈ 3650 (brushless)
550 (brush) ≈ 3656 (brushless)
775 (brush) ≈ 4268 (brushless)

Motor Turns vs Speed

Turns Watts Speed
2.5T 730W 11900Kv
3.5T 630W 10800Kv
4.5T 535W 9300Kv
5.5T 428W 7700Kv
6.5T 404W 6700Kv
7.5T 352W 6100Kv
8.5T 295W 5300Kv
9.5T 261W 4900Kv
10.5T 243W 4500Kv
11.5-12T ~ 3900Kv
13.5T 201W 3500Kv
17.5T 131W 2500Kv
21.5T 88W 2100Kv

Relationship between speed and voltage

30000 rpm is the best choice, the closer to this value the more efficient the motor will run. The relationship between brushless motor speed and voltage:

Speed 2s (7.4v) 3s (11.1V) 4s (14.8V) 5s (18.5V) 6s (22.2V)
1300Kv ~ ~ 19240RPM 24050RPM 28860RPM
1400Kv ~ ~ 20720RPM 25900RPM 31080RPM
1500Kv ~ ~ 22200RPM 27750RPM 33300RPM
1600Kv ~ 17760RPM 23680RPM 29600RPM 35520RPM
1700Kv ~ 18870RPM 25160RPM 31450RPM 37740RPM
1800Kv ~ 19980RPM 26640RPM 33300RPM 39960RPM
1900Kv ~ 21090RPM 28120RPM 35150RPM 42180RPM
2000Kv ~ 22200RPM 29600RPM 37000RPM 44400RPM
2100Kv ~ 23310RPM 31080RPM 38850RPM 46620RPM
2200Kv ~ 24420RPM 32560RPM 40700RPM 48840RPM
2300Kv ~ 25530RPM 34040RPM 42550RPM 51060RPM
2400Kv 17760RPM 26640RPM 35520RPM 44400RPM 53280RPM
2500Kv 18500RPM 27750RPM 37000RPM 46250RPM 55500RPM
2600Kv 19240RPM 28860RPM 38480RPM 48100RPM 57720RPM
2700Kv 19980RPM 29970RPM 39960RPM 49950RPM ~
2800Kv 20720RPM 31080RPM 41440RPM 51800RPM ~
2900Kv 21460RPM 32190RPM 42920RPM 53650RPM ~
3000Kv 22200RPM 33300RPM 44400RPM 55500RPM ~
3100Kv 22940RPM 34410RPM 45880RPM 57350RPM ~
3200Kv 23680RPM 35520RPM 47360RPM 59200RPM ~
3300Kv 24420RPM 36630RPM 48840RPM ~ ~
3400Kv 25160RPM 37740RPM 50320RPM ~ ~
3500Kv 25900RPM 38850RPM 51800RPM ~ ~
3600Kv 26640RPM 39960RPM 53280RPM ~ ~

How to choose a brushless motor?

A properly set up high voltage system will draw fewer amps than a properly set up low voltage system that generates the same power (Watts = Volts * Amps). A system that draws fewer amps will generate less heat.

Running 3s, 4s, 5s, and 6s in 1/8th scale vehicles depends on the motor. A higher voltage system will run cooler if you use an appropriate motor KV value.

How to obtain the appropriate set-up:

  • Choose the voltage you want to run.
  • Pick a motor that will give you around 30000 rpm with that voltage.
  • Gear it to the speed you want.

You just don‘t need the motor to spin faster than 30-40k RPM. This is a typical RPM range of a nitro engine and will be the most “driveable” configuration. If more speed is needed, you can adjust 1-3 teeth on the pinion gear without harm.

Relationship between size and speed

For the same size motor, the larger the Kv, the greater the operating power and torque.

Larger motors tend to provide more power and torque.

If you want to increase the maximum speed of the car, you can replace the motor with a larger size, or replace the motor with a larger Kv value. (Prerequisite: The vehicle has enough space and a suitable gear ratio.)

The smaller the size of the brushless motor, the higher the Kv. E.g:

  • 2030 brushless motor, 6000Kv
  • 4274 brushless motor, 2000Kv

Therefore, the power and torque of the motor depend on the Kv value. Size is the main factor that determines power and torque. Therefore, large-sized cars use large-sized motors with higher voltages.

Basic parameters of the motor

Turn

The number of turns indicates the number of turns the wire is wound, in T (or R). For example, if the wire is wound 21 times, the number of turns is 21T.

Low turns

Pros

  • Faster speed
  • More torque
  • Provide more power

Cons

  • Power consumption faster
  • Higher fever

Rotating speed

The motor speed is usually expressed by the Kv rating. For example, 3000Kv means that increasing the voltage by 1V can increase the speed of the motor by 3000RPM. Therefore, we can calculate the speed of the motor at 8.4V (8.4v*3000kv=25200RPM)

Motor shaft diameter

The motor outputs power through the shaft, common shaft diameter:

  • 2mm for 1/16 and 1/18 scale cars
  • 3.175mm for 1/10 scale cars
  • 5mm for 1/8 scale cars
  • 8mm for 1/5 scale cars

Frequently Asked Questions

Q: What is the difference between brushed and brushless?

A: Whether brushed motor or brushless motor, their basic principle is to generate a magnetic field through a coil, and then use a permanent magnet to drive the rotor to rotate. The brushed motor uses permanent magnets as the stator and coils as the rotor. The brushless motor uses the coil as the stator and the permanent magnet as the circular rotor.

Q: What is the difference between sensored and sensorless?

A: The sensored motor has a position sensor, which feeds back the position of the rotor to the controller. With this position information, the controller can accurately provide the corresponding current to drive the rotor. The sensored motor has a dedicated sensor wire that connects the motor to the ESC.

Sensored motor

Pros

  • Stable acceleration and better handling

Cons

  • High cost
  • Usually not waterproof

In contrast, a sensorless motor does not have a position sensor, it acquires the position of the rotor through random current changes at start-up, thereby controlling the current and direction.

Sensorless motors

Pros

  • Lower cost
  • Water proof

Cons

  • Acceleration is not stable enough

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