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The Detailed Comparison of the Advantages and Disadvantages for Mid-drive Motors and Hub Motors 

We will explain in detail the difference between Mid-drive motors and hub motors.

The mid-drive motor is like a delicious cake, which I want to say that it depends on your application, but it cannot be limited by this. The solution of a mid-drive motor is the ultimate winner when you start riding. I have listed a table below for your convenience. Please continue reading the following if you want to know the reason. 

Mid-drive motorMid-drive motorhub motorhub motor
Better torque = better climbing performanceA bit more expensivecheaper than the Mid-drive motorHeavy unsprung weight and uneven weight distribution (especially the front wheel hub)
better overall performanceThe drivetrain is more prone to wearThere are more on-site options for hub motors, suitable for DIYThe front drive requires a larger torque arm and a more powerful hub motor
Lower center of gravity distributionLack of a complete transformation plan,  mainly applied to a complete set of electric bicycles currentlyCan realize front and rear drive, AWD (All Wheel Driver) systemweaker climbing ability
Provides a higher maximum speed through gears Small changes on the transmission systemHigh speed is a bit limited

Now let’s get into the topic.

You will indulge and make all the desired performance improvements the first time you own an electric bicycle, which is a problem that has existed since the birth of electric bicycles. After three weeks of riding, you will look for better power and observe other motors. This behavior will be imperceptible to every electric bike rider, and even you will be addicted to some relevant forums at 3 in the morning, looking up some information, or even going to YouTube to watch a better reference video.

Wouldn’t you do this?

Next, I will analyze such problems for everyone who likes electric bicycles. Let us start with each type of motor to understand why a mid-drive motor is a better choice.

Mid-drive motors

Bicycles driven by hub motors are usually powered by DC motors, and usually brushless DC motors are more reliable and quieter (compared to brush motors). If you want to know the working principle of a DC motor, or the difference between a DC motor and a brushed DC motor, you can find many related popular science videos and some working principle animations on Youtube, which can help you understand many details of its working principle.

Let’s go back to the topic below and you will find the typical torque and power curves of a DC motor.

When using a DC motor, the torque is always maximum at zero speed, which is called stall torque. As you can see above, the torque of the motor decreases linearly with speed/rotation speed. The theoretical power curve will be parabolic with a peak somewhere in the middle.The picture below is the description of Fat-E Mini.

You can see that it is very similar to the theoretical curve. But the actual situation is much more complicated, such as friction, efficiency and improper matching, there are many irregular factors, but the curve of torque and output power seems to be quite accurate. As shown in the figure, what matters here is the area under the curve, not the peak torque or power. Car or mechanical enthusiasts will always tell you that machines with a larger area under the curve will outperform the smaller area especially since they produce the same number of peaks. Please remember the reason why we use the mid-drive motor method.

Mid-drive motor

When driven by a mid-drive motor, they are almost identical to the hub motor mounted on the bottom bracket of the bicycle. It connects directly to the cranks and gears. Because of this, you can get a better power/torque curve. Imagine the working dynamics of the motor, the dynamic torque and output power of each set of gears are shown in the following figure:

It looks a bit crazy, but what it outputs is the driving power of each gear. The curve gradually stretches when each gear is higher. Do you remember what we said about the power/torque diagram? The area under the curve really shows the performance of the machine, especially when their peak power/torque ratings are the same.

Assume that Hunter’s peak power number is the same as that of Fat-E Mini. Comparing the characteristics of each graph, you can get a mini curve of the power curve, and Hunter has multiple power curves (the same number as the gears assembled). These multiple power curves are basically combined, which will obviously be summarized as a large area larger than the power curve of the hub-drive motor (although this is not always the case, but it is usually like this). So mid-drive motors have obvious advantages in terms of power output performance.

Power and torque performance? Mid-drive motor

How to compare?

We should know by now that the mid-drive motor is mounted on the bottom bracket of the frame, and the battery/controller is mounted on the down tube. This makes the center of gravity of the bicycle very low and centered. When using a hub drive, the center of gravity is usually slightly higher than that of a mid-drive motor, and the center of gravity of the hub motor is usually higher whether it is the front wheel or the rear. I compiled a picture below with the Photoshop drawing. The black and white circle labels represent the center of mass.

Depending on the size of the wheel, the hub motor may be installed at a higher position or the same height as the mid-drive motor. Although the height of the center of gravity is similar, the front or rear hub shifts the center of gravity forward or backward. This will affect riding, especially the front wheel hub drive. The use of 3kg wheels will greatly affect the operation of the bicycle.

Compare the price, maintenance and other aspects of mid-drive motors with hub motors?

Frankly speaking, hub motors outperform mid-drive motors in almost all applications. The price of hub motors is surprisingly low, but maintenance costs are higher. The hub motors are more expensive than mid-drive motors when something goes wrong. Another thing to consider is that there are many options for hub motors in the market, which are also easy to install and retrofit. On the contrary, the mid-drive motor is completely different.

With the introduction of high-end mid-drive motor solutions designed and produced by Bosch, Shimano and Yama (for example) , they found that it is very difficult for ordinary modification, and it is almost impossible to fit your ordinary bicycle modification.  It is most unlikely to buy a Bosch mid-range drive on the weekend and install it on commuters unless you can customize and modify the frame. There are mid-drive kits available in the world that are suitable for the bottom bracket kit, but even so, the hub motor is easier to buy and easier to install.

Many people choose hub motors based on cost and some other factors.

In conclusion

Here you get a lot of information you want through practical experience, as well as magical ways to win in the application. Hope you can understand from a deeper level why the mid-drive motor is better, and share these with your friends! Remember, a key element of playing electric bikes is talking about it.

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