Inrunner Vs Outrunner

Inrunner Vs Outrunner: 4 Factors To Consider Before Choosing The Better Motor


Your brushless motor purchase is a very important decision to make. And brushless inrunner or brushless outrunner options could influence this decision. 

The verdict might get extremely complicated for you.

Which motor would you pick between inrunner vs. outrunner?

In the outrunner, the magnets are stationed on the piston. And on the inrunner motor, it’s placed in the center. The outrunner motor is less efficient than the inrunner motor. Both of the motors have decent heat dissipation.

This won’t be satisfactory for you to differentiate between the two motors. Have a look at the thorough comparison we’ve illustrated in this writing.

What are Inrunner and Outrunner Motors?

An electric motor with the rotor (runner) within the stator is referred to as a “inrunner.” Whereas, the rotor is located on the outside of the stator in case of outrunner motors. 

For the same construction volume, outrunner motors provide more torque than inrunner motors. The outrunner type is Magnetic Innovations’ area of expertise. However, despite each type of torque motor having distinct advantages, they both carry out the same basic tasks.

Inrunner VS Outrunner: Basic Differences

Now, let’s have a glimpse of the basic differences between inrunner and outrunner motor-

Features InrunnersOutrunners
RPM 3000-5000500-2600 RPM
Efficiency More efficient than outrunnersLess efficient than inrunners 
TorqueLow torque High torque 
Heat Dissipation Slower but even coolingFaster but pressurised cooling
SizeSmaller diameter, larger in length Larger diameter, smaller in length 
Weight2-4 lbs0.3-0.6 lbs

Still can’t concede to what you need? It’s alright! Ease up and avail yourself of a head-to-head contest.

Inrunner VS. Outrunner: Head To Head Contest

We realize only the fundamental contrasts will not be sufficient. Thus, partake in a straight-on contest between inrunner and outrunner.


Generally, this would be the more conventional sort of electric motor. Particularly in case, you know about huge AC motors or even old brushed DC motors.

What are the Differences in Size?

Brushless outrunner motors will have a larger diameter vs an inrunner motor of similar weights. Also, outrunner motors are smaller in length. Contrariwise, inrunners are compact in width and generally wider in height. 

Manual size is one sector that your requisition that may be restricted. However, other trade-offs would have to be evaluated as we will get into below.

Winner: Its a tie as both motors are different in size.

What’s the RPM / Volt (Kv)?

You should correctly select the appropriate Kv motor. Something else, the danger of wearing a power module out is enormously expanded. In case the power system wears out, check your brushless motor with a multimeter.

An inrunner engine of comparable size to a brushless outrunner engine will have massive Kv. Though motors with unique and identical bulk and Kv alternatives give a fair reach. Outrunner motors will generally have a poorer Kv quality. 

This is essential in your preference for a brushless motor to suit your requisition.

Winner: The winner for this category is the Inrunner motor as it has a higher RPM/Volt value.

Torque Comparison

The larger momentum converts directly into more torque being created. Hence the outrunner motor will normally generate more torque vs an inrunner motor. 

This relationship ties in with the fact that outrunners have a lower RPM/Volt. The association between Kv and torque is conversely relative. As RPM per volt (Kv) expands, the force of the engine diminishes.

Generally, this would be the more conventional sort of electric motor. Particularly in case, you know about huge AC motors or even old brushed DC motors.

Winner: The Outrunner motor wins here as it has a higher torque.

Does the Efficiency Differ?

This can be a tough comparison. Even the explanation has many reliances. These can be all you name it. 

From the constructive size correlation with the nature of the engine. To the constructor of the engine, power generation of the engine, and several more. 

For the most part, an inrunner engine is more systematic than an outrunner. So, it is considered more efficient.

But not all inrunner motors have thid edge over outrunners. Some bad quality ones tend to perform worse than the outrunners. For your ease, I’ve mentioned some of my favourite inrunner motors that never disappoints:

With added maintenance these motors will last a long time and provide good performance.

Winner: The Inrunner motor is more efficient so its the winner here.

What’s the Waste Heat?

How about we consider the temperature that an engine outputs? If your brushless motor overheats then it’s not a good brushless motor

If we take a gander at the outrunner engine, heat squanders through its focal point. The origin of calefaction is obviously the stator windings of the engine. 

The stator windings of the outrunner are situated at the center of the engine. The high temperature should move to the focal point of the engine being the engine shaft. Then it’s directed outward through the engine shaft. 

An outrunner’s answer for heat is to have enormous available cooling vents. On the off chance that to permit air to stream over the windings straightforwardly 

This immediate resource gives a magnificent surface. Furthermore, an extremely huge region for heat to move. 

Air is a terrible conductor of high temperatures. By expanding the measure of a surface region, an inrunner can dispose of abundant heat energy. 

Having the option to dispose of junk heat permits the inrunner to run cool. Furthermore, it’s more productive for comparable force generation on an engine of equivalent size/weight.

Winner: The winner of this round is the Inrunner motor as it cools down evenly.

Which One Makes the Most Noise?

Generally speaking, the inrunner brushless motor is very noisy. This is because it has higher RPM.

On the other hand, compared to inrunner motors the outrunner motors are quiter. They are small and has very little RPM so it tends to make less noise.

Winner: The Outrunner motor makes less noise so its the winner here.

Which One Requires More Maintenance?

Compared to inrunner motors, outrunner brushless motors require less maintenance. In general, the outrunner motor may be serviced by yourself because it dissipates heat more effectively. It is also less likely to burn out.

Because you cannot wind the enamelled wire manually, repairing an inrunner motor is more challenging.

You can easily find replacements more outrunners in the store or Amazon. Here are some of my go-to outrunners that I keep gravitating towards:

Using any one of these will cut down the cost of your maintenance a lot more.

Winner: The Outrunner motor is the winner here as it is easier to maintain.

Final Verdict: Which One Should be Your Pick?

The air gap surface of outrunner motors is substantially larger than inrunner motors. Nevertheless, this doesn’t recommend that you ought to favor outrunners over inrunner motors. Try to think about the speed and torque that you need in your motor.

If you want your motor to have higher RPM yet lower torque then opt for the inrunner motor. It is also more suitable for larger vehicles.

On the other hand, if your vehicle is small and you want higher torque then definitely choose the outrunner. It will save you energy and money as well.

If you’re still not sure regarding which one to get then check out this comprehensive video-

Select carefully and you will rejoice in better performance of your motor!


Are brushless outrunner motors waterproof?

The fact is brushless motors are sealed however they are not really damp-proof. Water is always adulterated in a pond or pool or downpour. That’s why it delivers small crumbs to the bearings in a brushless motor.

What does a brushless machine do?

In construction, brushless engines are generally utilized for movement control. Brushless engines are preferably fitted for construction implementations. Given their power substance, great speed-force attributes, high productivity, and easy care.

How long do brushless inrunner motors last?

Generally a brushless motor (inrunner or outrunner) has a long life expectancy. They can attain a huge number of hours normally. As there are no brushes.


Hope we’ve demonstrated everything to assess between inrunner vs. outrunner. You shouldn’t have any trouble now picking between these two.

Let us know which one you’ve decided to go with.

Until then, take care!

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