Types of E-Bikes

Electric bicycles are not new technology, but there are many different types of e-bikes. In fact, the first motor-propelled bicycles were documented with various US patents in the late 1890s, but the technology never really gathered steam, so to speak. In their modern incarnation, electric bicycles with torque sensors and power controls were developed in the 1990s, quickly gaining popularity in China and India, but remaining relatively slow to catch on in other parts of the world. 

With the rapid global trend toward urbanization and the welcome retreat of car-dominance on city streets, e-bikes are now quickly growing in popularity around the world. Fulfilling the promise of flattening hills, extending distances, and lightening the load, electric bicycles are a viable transportation choice for busy, active lifestyles that won’t break the bank. The transformative impact this technology will have on the urban form is only now beginning to reveal itself.

When looking for the right e-bike the technology and number of options may seem daunting but by outlining the different types of e-bikes available and a briefer on the technological components we hope to make this process a little easier for you. E-bikes can be roughly grouped into two main types, based on the location of their motor. Hub motors are located in the wheel, replacing the regular hub, while mid-drive electric bicycles have the motor located on the frame.

HUB MOTOR E-BIKES

There are two different kinds of electric hub motors:

Direct drive hub motors are larger, and use the entire hub shell as the motor. They’re faster and more durable, but have less torque. They’re also heavier and have a bit of drag, resulting in less overall efficiency. These motors are always engaged and therefore can have regenerative braking, which will return some small amount of energy to the battery. As they have no moving parts, they’re almost completely silent.

Geared hub motors are smaller and lighter than similarly powered direct drive motors, they could pass for a regular wheel hub. They tend to have greater torque, but have a lesser top speed than direct drive. They have a free-wheel, which means there is no resistance when the motor is not being used, but means you can’t have regenerative braking. Geared hub motors also have moving parts, which means that when they are engaged there is a noticeably louder hum than an equivalent direct drive motor, and they may out a bit faster.

Hub motors can be located on either the front or rear wheel, each option having its own benefits and drawbacks. Front hub motors provide an “all wheel drive” sensation, with the rider’s pedaling propelling the back wheel and the front wheel being “pulled” by the motor, a sensation which some riders appreciate and others dislike. Front hub motors are much easier to install and maintain as they don’t interfere with the drivetrain or gearing, but have the tendency to spin out on occasion as there isn’t much weight over the front of the bike.

Rear hub motors can handle higher power options, because the frame is better equipped to handle higher torque at the back than in the front, and can provide throttle, cadence, and/or torque sensor pedal assist, whereas front hubs generally can’t offer torque sensor pedal assist. Rear hub motors are more cumbersome to install and maintain as they need to be worked around the drivetrain, and tend to be quite back-heavy if the battery is also located towards the back of the bike, but are often preferred for offering a riding style more similar to a conventional bicycle.

             
E-Bike Hub Motor                                                                 E-Bike Mid Drive

MID DRIVE ELECTRIC BICYCLES

Mid drive systems mean the frame has been specifically designed to incorporate the motor on or next to the bottom bracket. This design has the advantage of using the standard drive-train of the bicycle, which allows it to use whatever gears are on the bicycle. In this system, if the rider changes the gears appropriately, the motor can turn closer to its ideal rotations per minute (RPM) whatever the speed of the bicycle, and be more efficient as a result. Conversely, hub motors cannot be geared to adjust their RPM as the bicycle speeds up, so they have a tendency to get “bogged down” on steep climbs. Mid-drive systems tend to feel more like a “normal bike,” since they drive the pedals, just like your legs, and those who frequently climb long, steep hills tend to prefer mid-drive systems for their ability to handle long climbs. As they can leverage the bicycles lowest gears for climbs, mid drive systems can also leverage the high gears to reach higher speeds on flat areas than a hub system.

Mid drives tend to have better weight distribution than hub motors since the motor is located at the cranks, creating a lower center of gravity and a more balanced ride as a result, especially if the battery is also mounted in the center of the bike. 

Since the electric components of the bicycle are on the frame, mid drive bicycles make it easier to do simple repairs such as changing a flat, and are compatible with any wheel type. However, since they provide the power through the chain drive of the bicycle, they may see somewhat faster wear on those components than a hub drive e-bike that reduces the load on the chain drive. They also work best when the rider rides like a “normal bike,” utlizing the gears appropriately in order to keep the legs and motor working efficiently, a task some riders would prefer not to do.

RETROFITTED E-BIKES

It can be a fairly simple process to retrofit an existing bicycle to electric assist. There are a number of after-market e-bike conversion kits available to turn almost any bicycle into an e-bike, depending on your needs and your budget. It should be noted that while this can be a simple process, the new generation of purpose-built e-bikes generally provide a much better user experience, higher degree of integration, and a better ride.

Hub motor conversion kits:
The most common e-bike conversion kit uses a hub drive motor. Generally the process involves replacing either the front or back wheel with one that has a hub motor, then running the wiring to the motor controller and the battery, which is mounted on a back rack or in the place of a bottle cage. You can then choose whether you’d like a pedal sensor or a throttle to control the amount of motor assistance.

Mid drive conversion kits:
There are also e-bike conversion kits for people who want mid-drive motors, which doesn’t require the replacing of a wheel, but will require affixing a motor to a frame which was not designed to carry it, a transformation which is a little more difficult and isn’t suitable for all types of bicycles. At present, there are many more e-bike conversion kits available in hub drive than mid drive, but availability of the latter is on the rise.

All-in-one wheel kits:
The newest entrance into the market are all-in-one wheel motors, which house the motor, battery and controller into one hub or wheel. Companies like Super Pedestrian and FlyKly are pioneering this form of conversion kit, which only requires installing a new wheel and a small frame controller. These kits have the advantage of keeping the bike super clean looking – many people won’t even realize it’s an e-bike – and often come with smartphone integration and bonus features such as auto-locking. However, as they’re a very specific technology, maintenance will require sending the system back to the company rather than taking it to a bike shop. Though the products have been developed, the technology is still so new that it is not yet available for purchase. Something to keep an eye out for.

Friction drive:
Last, and least common, are friction systems which involve a motor-controlled roller being installed onto the seat post above the back wheel. The roller sits on the wheel, and adds propulsion through friction with the wheel. These are simple systems which are easy to install and maintain, but are also considerably less powerful than more integrated systems.

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In this guide we explore some of the different ways an e-bike can provide solutions for different users, outline the different types of e-bikes available, give a briefer on the technological components, and offer some advice on purchasing your own electric bicycle.

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