Electric bicycle hub motors vs mid-drive motors
Electric bicycle hub motors vs mid-drive motors: Which should be on your next e-bike?
Electric bicycles are becoming increasingly popular forms of two-wheeled electric transportation for both commuting. The two common electric motor styles used in today’s electric bicycles are hub motors and mid-drive motors. Which one is best for your needs? Read on to learn more and find out!
The hub motor places the motor at the center of the bicycle wheel and is undoubtedly the most common form of electric bicycle motor.
The mid-drive motor installs the motor close to the center of the bicycle and transmits the power of the motor to the rear wheel through the bicycle chain drive. It has become more and more common in the past 2-3 years, and the hub is being significantly reduced.
Motor leads the king of electric bicycle motors. Both have many unique advantages and disadvantages, so choosing the right motor for you depends largely on your requirements and which advantages seem to be more useful for your needs.
Advantages of hub motor for electric bikes
One of the biggest advantages of in-wheel motors is that they require little maintenance. They are a completely independent drive system that keeps all components inside the motor housing and will not let you mess up or maintain anything.
A closed system also means that the probability of failure is much smaller. There are two types of hub motors: geared hub motors have internal planetary gears to reduce the speed of higher RPM motors, while gearless hub motors have no gear transmission and connect the shaft of the lower RPM motor stator directly to the bicycle. Geared hub motors usually have only one weakness: gears. Over time, the teeth will break and the reinforced nylon gear will eventually fall off.
On the other hand, gearless hub motors have zero moving parts in addition to bearings, so there is basically nothing to wear. As long as they do not rust or wear bearings, they can be used almost forever.
Compared with mid-drive motors, in-wheel motors also help reduce other bicycle maintenance tasks. Since they are not connected to the main pedal drive system, the in-wheel motors will not put any extra pressure on your chain or gear lever, nor will it cause any of these components to wear faster. If anything, your chain may last longer than a non-electric bicycle, because the hub motor will do more work, leaving your chain idle often.
As an independent drive system, the in-wheel motor also adds redundancy. Since the hub motor and pedal drive system are completely independent, you may lose one, but you can still use the other. The chain broke when you hit hard on the road? Throw the chain into your bag and you can ride home with electricity. The hub motor fails somehow? Pedal back. Either way, you have a backup. This can be huge if you are far from home, especially for older riders or people who use electric bicycles as a form of rehabilitation.
Depending on the situation, the weight of the in-wheel motor will have a positive and negative impact on the balance of the bicycle. In some cases, it may be good to have the weight of the motor farther forward or backward in one of the wheels. This is especially true for electric bicycles with rear-mounted batteries. In this case, the front hub motor can redistribute the weight so that the center of gravity remains at the center of the bicycle.
Finally, in-wheel motors are much cheaper than mid-drives. The mass production volume of wheel motorcycles is hundreds of thousands or even millions, depending on the factory. In some cases, the same design has been used for more than ten years. This means that the price is very cheap.
As mentioned in some of our past DIY electric bike articles, you can get a complete set of 1,000 W hub motor kits, including electronics, throttle, etc., for less than $200. The same power level in the mid-drive kit can easily cost 3-4 times.
Electric bicycle hub motor disadvantages
Of course, in-wheel motors are not perfect.
Perhaps most importantly, almost all in-wheel motors only allow one gear ratio. Although this is generally suitable for cruising on flat ground, lower speed but higher torque gears are more suitable for mountain climbing. When operating in a lower RPM range under load, using a single-speed motor is not efficient.
The hub motor is usually heavier than the mid-drive, and this weight is the unsprung weight on a shock-absorbing bicycle, which reduces the effectiveness of the bicycle’s shock absorber and transmits more bumps to the rider.
When it comes to wheel components such as rims, tires, and flywheels, in-wheel motors may be more restricted. Since you are limited to the rims that come with the in-wheel motor, you may not be able to fit your favorite tires, and the width of the in-wheel motor usually excludes flywheels above 7 speeds.
Tire replacement for in-wheel motors is also more difficult, because you must often disconnect the motor cable or wrestle with a heavy wheel while it is still tied to the bicycle. However, there are some really cool bicycle inner tubes that can be replaced without removing the bicycle wheel-perfect for hub motors.
Front vs rear hub motors
The in-wheel motor can of course be installed on any wheel, and this difference will also produce some other unique advantages and disadvantages.
Because more weight is usually concentrated on the rear wheels, the front hub motors can help balance the weight better.
The front wheels also usually have fewer punctures than the rear wheels, because they often raise road debris and prepare the rear wheels. The front hub motor keeps the rear wheels intact, making it easier to change the inner tube and tires.
The lighter the weight of the front wheel of the bicycle means the less traction, so the more powerful front hub motor can sometimes cause burns when the accelerator is stepped on. In addition, the front fork is not as strong as the rear fork, so a powerful front hub motor can even damage the front fork over time, although this can be alleviated by installing a device called a torque arm. A powerful hub motor of 750 W or higher is usually best installed at the rear of the bicycle.
The rear wheel hub motor has better traction and stronger frame installation advantages.
When turning at higher speeds, they will not produce a slightly strange gyro effect.
Perhaps my favorite thing about the rear hub motors is that they give you more of a motorcycle’s push, rather than the pull of the front motor.
However, once you reach a stable speed and drive in a straight line, the difference between the front and rear hub motors is almost unnoticeable.
Electric bicycle mid-motor advantages
The mid-drive motor is designed to improve many of the shortcomings in the in-wheel motor.
The biggest advantage of mid-mounted motors over in-wheel motors is their gear ratio. They allow the rider to power the rear wheels through the same chain and gear set as the pedals, which means low gears can be selected to power steep hills or accelerate from a stop with high torque. Low-speed mid-drive motors can climb steeper hills than hub motors of similar power, and take longer to climb than hub motors. The hub motors may overheat during prolonged steep climbs.
Mid-drive motors are also generally smaller and lighter than in-wheel motors of similar power. Smaller, lighter mid-drive motors are usually more concealed because they can be integrated directly into the bicycle frame. Many people don’t even realize that medium-sized motorcycles are electric bicycles.
It’s much easier to replace the tires of a mid-motor electric bike because you don’t have a heavy-duty hub motor to deal with. You only need to replace it like an ordinary bicycle. In addition, since you can use ordinary bicycle wheels, you can use any wheels, tires, and flywheels at will.
Finally, the mid-drive motor allows the use of a true torque sensor for the pedal assist system, which adjusts the motor power based on the pedaling force you measure at the crank. Hub motors usually rely on a cadence sensor for pedal assistance, which only adjusts the motor speed based on the pedal speed, and may cause the motor to jitter or be awkward, especially when climbing a mountain or moving the bicycle around obstacles.
Electric bicycle mid-motor disadvantages
Of course, this coin has another side. Mid-drive motors can be cruel to your drive system, and this may be their biggest flaw.
A healthy person can output 100 W of power for a long time, but it is reasonable to output 250 W of power during a hard sprint. But the mid-drive motor can continuously output 250-750 W of power. It’s like having a professional cyclist step on your pedals all day long. Cheap bicycle chains have no chance at all. Break!
For this reason, retail mid-mounted electric bicycles are usually equipped with upgraded bicycle chains, because chain breaks may be the number one maintenance problem for mid-mounted electric bicycles. And because both the motor and the pedal need chains to drive the wheels, riding a mid-motor electric bicycle with a broken chain is a strict downhill job.
One way to completely alleviate the chain problem is to choose a mid-drive electric bicycle with a belt drive, but also take the increased price into consideration.
Due to the increase in the number of moving parts in the central drive motor, there are more failure points. If the motor does fail and its motor is directly built into the frame of the bicycle, replacing the hub motor may be more expensive than replacing the hub motor.
In fact, in general, mid-drive motors are also more expensive than the tried-and-tested, mass-produced hub motors on many electric bicycles.
The mid-drive motor has another disadvantage, and many people don’t consider it until the first stop. Unless the bicycle is moving, you cannot change gears (except for bicycles with internal gear rear hubs, which are rare). This means that if you are at the highest gear while flying on the street, but are then forced to stop at a red light, you need to remember to downshift before stopping. Otherwise, when you try to stay away from the light, you will be stuck in the highest gear and your acceleration will be affected.
Don’t even consider shifting gears under the power of a motor. This is the best way to split the chain in two. The torque in the motor is too large. When the chain is between the gears, the extra pressure can easily break the chain. Better mid-drive electric bikes have a shift interrupter that cuts off the throttle briefly when you change gears. But many electric bicycles do not have this function, so the rider should remember to relax the throttle when shifting gears. No grandma transfer!
So what is the verdict?
The most annoying answer: it depends!
Mid-drives have many improvements over the old in-wheel motor technology, but they have their own unique problems. There is a reason why in-wheel motors have been around for so long-they can work.
The main advantages of mid-drive include lighter weight and better gear usage, which makes them more suitable for off-road use and people who need to cross hilly terrain.
On the other hand, in-wheel motors are fairly bulletproof and low maintenance costs, so they are generally more suitable for commuters and those who want simple, reliable electric bicycles that require little maintenance.
However, many off roaders like the power and reliability of hub motors, and many commuters prefer lightweight, stealthy and unobtrusive mid-drive motors. It really depends on which features fit you best.
At the end of the day, the best e-bike motor is the one you have. So just get out there and ride!
What type of e-bike do you have, or which would you prefer to buy? Let us know in the comments below.