Because of the many different types and sizes of RC cars, and the big range of different products available, choosing a suitable electronic speed control (ESC) and motor for your car can be a challenge. If you’re thinking about buying a new ESC and/or motor, the thing first on your mind is often speed, but there are numerous things to take into account, so here we’ll go through the basic things you need to know.

ESC

Starting with the speed control, the choice is very much dependent on what motor you plan to run, as the ESC and motor need to be compatible between each other. Basic things to consider is first if the ESC needs to be for brushed or brushless motors. For most uses today you’ll be looking at a brushless ESC, however, you then need to pay attention to if it is for sensored or sensorless motors, or if it can handle both types.

Finally you also need to check that it can handle the type of battery voltage and motor specs you have in mind. ESC’s typically have some sort of motor limit (in kv or turns), which you need to adhere to. If the ESC specifications says that the motor limit is 8.5T on a 2S battery, then you must use a motor with 8.5 turns or more. If a kv rating is used, then you need to choose a motor with a lower kv value than the limit.

Other ESC related factors to take into consideration include the size of the ESC, making sure it fits properly into your car. Additionally, some ESC’s are waterproof or protected, while most are not, so you also need to consider if this is a feature you need.

A more expensive ESC will usually give you better control, more features and adjustability, as well as better overall quality and lifetime.

Motors

With motors, the first thing to check is the actual size and measurements, as there are various motor sizes available for different types of cars. The car specs usually specify what size of motor the car is designed for, so do check this before making a choice if you are unsure.

What’s perhaps still the most common motor size used in RC cars, is often called “540”. These are used in many lighter 1/10 cars, while larger “550” or “1/8” sized motors are often used in heavier 1/10 vehicles and 1/8 scale cars. Brushless motors in this size are today often “4-pole” motors. Smaller motors (like 370 or 380) are used in some smaller cars, while large scale cars use even larger motors.

In addition to differences in length and diameter of the actual motor, there are also differences in motor shaft diameter. The most common shaft size is 3,175mm (1/8”), while many larger motors use a 5mm shaft. The shaft diameter directly influences on the selection of gears available.

The mounting hole positions in each motor are also depending on its size, so because of all these factors, it’s very important to check what motor fits your car.

Another thing to decide on is brushless or brushed, but with the development in brushless technology over the past 15 years, in most cases this is no longer a factor to spend much time considering. Unless you use your car in some very specific class or conditions, we’ll almost always recommend a brushless setup. Do remember though, that if you are changing from a brushed to a brushless motor, you will also have to get a brushless ESC.

Brushless motors are available sensored or sensorless, the difference being that the sensored motors have sensors inside the motor that register the position of the rotor. The sensored motors are more responsive from low rpm and give a more precise feel, and is therefore used more in competition than the sensorless motors. The sensorless motors are simpler and usually more affordable, and often used in RTR’s and for more general hobby use.

Again, it's important to remember that motor and ESC needs to be compatible. Some ESC's can only power sensorless motors, while other only work with sensored motors.

The power of a motor is usually indicated in “kv” or “turns”, or both. A motor’s kv refers to its rpm per volt of electricity. This means that a 3000Kv motor will spin at 25200rpm at 8.4V (3000 x 8.4 = 25200). Turns are often used in place of kv to indicate power on 540 size motors, especially 1/10 competition motors. The turn number, like 8.5T or 13.5T, refers to the number of times the wire in the motor is wrapped around the stator. To make it simple - the fewer the turns, the more power the motor produces.

With all these turns and kv’s, it’s important to remember that different cars require different things, and it’s not only about rpm’s. The larger and heavier a car is, the more important it will be to have enough torque, meaning that for a heavy 1/8 vehicle, a low kv but high torque motor will often be the better choice.

With any motor choice, it is vitally important to have the right gearing. So if you’re planning to change to a significantly different motor from what you have been running, always remember to change the gearing at the same time, following the motor manufacturer recommendation to start with.

Going to a higher power motor will also shorten runtime on one charge, and produce more heat.