RC Brushless Motor Size Chart: Choose The Best

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 or 1/12 scale on-road and drift cars, 1/10 or 1/12 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

Added: 2435 motors are suitable for 1/14 – 1/18 scale cars, most have 2mm axles, but some have 3.17mm axles. 20mm or 24mm motors are usually only available without sensors.

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

Tips: Due to the different manufacturing materials of motor suppliers, the data has slightly deviated.

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.

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.

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.

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.