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Electric Bike Motors Explained

Electric Bike Motors Explained

Electric bikes are currently a booming sector within the bike industry. In the Netherlands, for instance, where electric bikes are leading the way, e-bikes made up the majority of bikes sold in 2018, and in the United States, the number of electric bikes sold in 2017 grew a whopping 25% from the previous year.

The hot trend of electric bikes has given rise to what can seem like a daunting array of customizable features, not the least of which concern the motor. The placing, composition and mounting style of your motor can alter the feel and performance of your bike — read on to learn how to determine which motor is right for you.

Types of Motors: Hub Motor vs. Mid-Drive Motor

Though there are a few other types of electric bike motors available, hub motors and mid-drive motors are the most popular options, so we will delve into the details of those two here.

More common than mid-drive motors, hub motors are installed directly inside the hub of the bike's front or rear wheel. With a hub motor electric bike, the motor system is entirely independent of the drivetrain of the bike.

A mid-drive electric bike, on the other hand, incorporates the drivetrain of the bike. When integrated with a derailleur-type drivetrain, it uses the gears and chain for power.

Hub Motor Benefits

E-Bike Hub Motor Benefits

  • Durability: Because they remain fixed in place inside the solid, sturdy hub, hub motors impose little wear and tear on the bike. The positioning of the motor is such that the hub is unlikely to need many repairs throughout its lifetime.
  • Easy maintenance: Because they are self-contained, maintenance on a hub motor will not necessitate upkeep on the complex drivetrain.
  • Compatibility with different drivetrains: Thanks to the isolation of the motor, it is ideal for bikes with all different types of drivetrains, from derailleurs to belt drives and internally geared hubs.
  • Versatility: The motor's independence from the drivetrain allows for completely separate power options. If the chain or pedals break, the bike can still operate on electric power. If the motor fails, it's easy to resume biking by using the pedals alone.
  • Cost: The popularity of hub motors has led to refined designs and easy production, so the purchase of a bike with a hub motor delivers an impressive bang for a reasonable buck.

Hub Motor Drawbacks

  • Push/pull: The rider of a bike with a hub motor may feel either pushed or pulled along by the rear or front wheel, depending on the mount of the motor. New riders of electric bikes may take some time to get used to this feeling.
  • Uneven weight distribution: This issue pops up more frequently with a rear-mounted motor, but it can occur with a front-mounted motor as well. With the motor and battery weight often concentrated in the back of the bike, the bike will be back-heavy and more challenging to transport.
  • A little less range: Because of the integration between a mid-drive bike's motor and its gears, the conservation of electric power leads to a bit more efficiency. This efficiency gives a mid-drive motor a slight advantage in range, allowing for longer rides or more rides between charges.

Mid-Drive Motor Benefits

  • Torque: The mid-drive motor harnesses the torque generated through the drivetrain, resulting in quick acceleration and superior power for steep climbs.
  • Even weight distribution: As the name suggests, a mid-drive motor typically gets mounted in the middle of the bike, between the pedals. This central positioning leads to more even distribution of weight and results in enhanced handling and an easy ride, as well as ease of transport.
  • Sensor systems: Mid-drive motors are relatively new types of bike motors, and as such, they often come equipped with novel sensor systems, particularly related to pedal assist and gear shifting. Some of these systems will, for instance, predict when the rider is about to change gears and alter the power output of the motor accordingly, resulting in a smoother transition.

Mid-Drive Motor Drawbacks

  • Limited drivetrain compatibility: Most mid-drive motors require a typical derailleur-type drivetrain and are incompatible with internally geared hubs and belt drives.
  • Excessive wear and tear: The force that passes through the drivetrain as it powers the motor results in quite a bit of wear and tear on the bike gears and chain, which will need more frequent replacement. This increased wear results in an increased burden of maintenance and a higher cost associated with repairs.
  • More difficult maintenance: Along with that wear and tear inevitably comes maintenance, and this upkeep is more complicated because the mechanic must first disengage the motor from the drivetrain. Even a flat rear tire is more complicated to fix on a bike with a mid-drive motor for this reason.
  • More challenging gear-shifting: On bikes that do not come equipped with sophisticated sensor systems, the rider must shift gears precisely to avoid interfering with the motor and causing a jarring shift. For expert riders, this requirement may not be difficult to adjust to, but for beginning riders — who often prefer electric bikes precisely for the easy, enhanced rides they promise — it may prove an obstacle.
  • Cost: Because mid-drive motors are newer and more complex motors, the bikes that use them often come with hefty price tags.

Types of Hub Motors: Geared vs. Direct Drive

Though mid-drive motors generally operate the same way, categories of hub motors break down further into geared and direct drive motors.

Direct-drive motors are simpler. Their construction is more or less like an extension of the wheel, with the axle of the hub also serving as the axle of the motor. An array of magnets encircles the hub, with copper windings attached to the axle. When an electric current runs through these components, the resulting magnetic field propels the wheel forward.

When the motor turns, it spins the wheel directly. The motor cannot run faster than the speed of the bike.

A geared motor is more complicated, but can be lighter and smaller. Like the gears that make up the drivetrain, the gears of a geared motor are interconnected and can spin many times to turn the wheel once. No one wants a bike to suddenly start rolling as fast as a whirling gear — it would turn into a zooming, bucking bronco of a bicycle in a heartbeat. The gear composition allows the motor speed to remain high and efficient even as the bike rolls along at a leisurely pace.

Direct-Drive Motor Benefits

Electric Bike Direct-Drive Motor Benefits

  • Speed: The only limit on this motor's speed is the speed the rider can pedal, so the large motor of reaching high velocity under the right conditions.
  • Durability: With no array of small, complicated gears that will wear down, a direct-drive motor can lead to a long-lasting bike. That makes it a smart choice for someone looking to maintain a ridable bike with little motor maintenance.
  • Noise reduction: The absence of turning, whirring gears makes the direct-drive motor quieter than a geared motor. If a quiet ride is a deciding factor, a direct-drive motor may be an excellent choice.

Direct-Drive Motor Drawbacks

  • Weight: Because of the one-to-one correlation between the speed of the motor and wheel rotation, the motor has to be large and heavy to produce a lot of power. The large array of magnets adds a good deal of heft and will make for a less efficient and more difficult bike to ride.
  • Less torque: This type of motor provides less power, which leads to slower acceleration and a more sluggish ride up hills.
  • Drag: The heavy, cumbersome nature of the motor naturally leads to drag, which makes pedaling significantly more difficult.

Geared Motor Benefits

  • Lightweight: The absence of large, clunky magnets allows a bike with a geared motor to zoom and zoom.
  • Power: The gear assembly allows the motor to translate the motor speed in torque. Acceleration and hills will be no problem for this motor.
  • Ease and efficiency: The light weight of the motor means a reduction in drag, which translates into ease of pedaling and a more efficient bike.
  • Range: A relatively unencumbered bike uses less energy and can go farther between battery charges.
  • Discretion: The smaller motor hides easily within the hub, camouflaging the electric apparatus and giving the appearance of a standard bike.

Geared Motor Drawbacks

  • Wear and tear: The small, complex moving parts of the gear assembly are more prone to wearing out. This type of motor will require a modestly increased amount of maintenance over a direct-drive motor. That is especially true for bikes that do heavy duty, often accelerate quickly or pull weighty gear like trailers.
  • Noise: The gears also produce audible whirring sounds, leading to a slightly noisier ride.

Hub Motor Placement: Rear-Mounted vs. Front-Mounted

The last feature to discuss involves the difference between a rear-mounted and front-mounted motor. Though the placement of the motor might seem a trivial choice, it has significant consequences for the rider and bike.

Front Vs Rear Mounted Hub Motors

Front-Mounted Hub Motor Benefits

  • Versatility: Because the front wheel is independent of the drivetrain of the bike, a front-mounted motor will work with any drivetrain, from derailleurs to belt drives to internally geared hubs.
  • Easy handling and carrying: Having the motor mounted in front means weight is more evenly distributed over the bike, whose battery and gears are often mounted in the back. The even weight distribution makes for more effortless transport, though lifting the front wheel over a curb while out in the streets may be more challenging.
  • Easy maintenance: Because the front-mounted motor is separate from the rear-mounted gear system, installing and removing the motor if necessary is uncomplicated.

Front-Mounted Hub Motor Drawbacks

  • Diminished traction: In essence, with a front hub motor, the bike ends up having all-wheel drive, with pedal power coming from the rear and motor power coming from the front. Although this configuration might seem to lead to better traction, it paradoxically leads to the opposite. That is because, whereas the passenger weight is over the rear wheel to keep it steady, the motor weight is too negligible to provide much of a stabilizing effect. The result is a wheel that may spin or slip.
  • Diminished power: Power, along with the resultant swift acceleration, tends to exacerbate the diminished traction described above. For this reason, the power of a front-mounted motor must remain low for the rider's safety.
  • Pulling sensation: The front mounted-motor creates a sensation that the bike is pulling the rider down the road. Though this feeling is not hard to get used to, it may unnerve some new riders. With rear-mounted motors, the pushing sensation is not too much different from the feeling of riding a regular bike, which is also powered by the rear wheel via pedaling.

Rear-Mounted Hub Motor Benefits

  • Traction: Because the motor is in the back, there is no excessive power to the front wheel to make it slip.
  • Torque: Due to the rider's stabilizing weight over the rear wheel, power coming from the rear wheel is much less likely to make the bike slide and spin. The stronger fork in the rear of the bike is also better suited to holding the heavier, more powerful motors. Therefore, much more powerful motors of up to 750 watts and beyond are available for a rear-mounted configuration. Mounting the motor on the rear is an easy way to add torque to a bike safely.
  • Discretion: A rear hub motor can easily hide among the gears at the back of the bike, making a rear-mounted motor much more discreet than a front-mounted one. Though electric bikes are enjoyable and safe, and there is no pressing need to camouflage them, this feature will please customers who wish to blend in with the regular bikes on roads and trails.

Rear-Mounted Hub Motor Drawbacks

  • More complicated installation and maintenance: Rear-mounted motors are more complicated to install and maintain because removing the rear wheel requires interfering with the drivetrain.
  • Uneven weight distribution: Though a rear-mounted motor leads to more traction in general, the fact that the rider, motor and often the battery weight are all at the rear of the bike can lead to more difficult handling — even sometimes popping a wheelie, which is fun when it's intentional, but a nuisance when it is not. The extra weight concentrated in the rear also leads to a bit of difficulty in carrying the bike.
  • Extra wear and tear: All that weight concentrated at the back also leads to an increased rate of wear tear on the bike's rear components. The lifespan and level of maintenance for the bike are factors to consider here.

Since much of the functionality of the bike involves the rear wheel, especially in terms of torque and stability, it makes sense to incorporate the motor there for a more integrated system. For riders who intend to engage in off-road travel or even just venture off paved streets, a rear-mounted motor is ideal, since a front-mounted motor is extra likely to cause the bike to handle poorly on unstable surfaces like gravel or loose dirt.

Electric Bike Motors From Juiced Bikes for Power, Range and Control

When it comes to selecting the right bike for your needs, goals and riding style, picking the right setup is crucial, especially the motor that gives electronic life to your machine. There are pros and cons to each type of motor discussed above, and your choice will depend on what features you hope to maximize.

A hub motor will give you durability, versatility and a top-rate setup for your costs. A geared hub motor will give you range, efficiency and an effortless ride. A rear-mounted motor will give you the power and stability to adventure and cruise like a pro. Choosing these features will let you make the best of all the advantages an electric bike has to offer.

Browse Our Selection of E-Bikes

If you're shopping for an electric bike to elevate your ride with, browse our extensive online catalog to find the right bike to suit any needs. At Juiced Bikes, we offer free shipping on every e-bike we sell, and each bike requires minimal assembly out of the box so you'll be cruising on your new e-bike in no time! If you have questions, call 888-303-8889 to speak with a member of our customer support team.