There are different types of motors for electric bikes. They differ mainly by two parameters: their position on the bike, and their quality.
The different position of the motor on electric bikes.
The motor of an electric bike can be placed on the hub (the center of the wheel) front or rear, or between the pedals.
Motors on the Front hub
Motors on the front hub: easier to install and often less expensive, they are the ones used by conversion kits
They are easy to install because they do not interfere with the pedals or chain. On the other hand, there are some problems with these motors: they create an imbalance in the weight of the bike and are not very effective on slippery asphalt (rain) or uphill, because the front wheel can slip. They also increase the load on the front fork, which we recommend you replace with a more durable fork. We recommend front hub motors only if you plan to use the bike on simple and mostly flat routes.
Rear hub motors
This type of motor avoids the above mentioned wheel slippage. They are generally more difficult to mount because they can interfere with the rear derailleur. They have the disadvantage of making it more difficult to remove the wheel to change the tube in case of a puncture, since it is then necessary to remove the wires that connect the motor to the battery, to avoid breaking them, a rather delicate operation. Rear hub motors are very suitable for urban use or trekking, so many bikes, even high-end ones, are based on this model.
Mid drive motors are the best solution, even if they are more expensive. They act directly on the chain and are therefore more efficient. They also do not prevent the wheels from being assembled and disassembled, and they allow for a better distribution of the bike’s weight. A few years ago, motors could only be mounted in this position with a bike that was designed from the ground up to accommodate them, but today there are many kits with center motors that are easy to mount. The center motor is the only viable option for electric mountain bikes, and for us it is the ideal solution.
Other differences between hub motors and center motors
There is also a difference in the rotational speeds of the two types of motors. Hub motors (also called “hubs”) are linked to the number of rotations of the wheel they are on. This explains the fact that when the wheel turns slowly, the motor must provide its maximum power at low speed, thus inefficiently, absorbing a lot of energy from the battery. The same principle is found on a steep slope, when the wheel speed drops because of the low speed. Conversely, the motors mounted on the crankshaft, acting on the transmission, can still turn at an optimal speed – if you use the derailleur efficiently – while consuming less energy.
Typically – but there are exceptions – hub motors are coupled to force sensors, which measure the rider’s effort, and allow for more natural pedaling. Hub motors – again, exceptions aside – are combined with simple pedaling sensors, which determine a less natural pedaling, while allowing for “symbolic pedaling”. The debate among aficionados as to the best type of motor is open and sometimes even heated. The general opinion we share is based on the budget and other parameters: if you have a tight budget, intend to use the EAB on small routes and reasonable slopes, and are interested in “symbolic pedaling”, you will opt for a front or rear hub motor. If you have a more flexible budget, are planning to use the electric bike on long trips and steep climbs, and your pedaling habit makes the use of “symbolic pedaling” unnecessary, then you would be better off with a central motor.
It must be said that the market seems has recently moved in the direction of central motors, preferred by almost all major companies (Bosch, Yamaha, Shimano, and recently Bafang).
Brushless motor or not ?
Electric bikes motors can be divided into two main categories: brushless motors and brushed motors. Without going into technical details, brushless technology is the most advanced: its main feature is that it is not necessary to install a contact system attached to the rotor blades.
Simply put, the brushless motor is lighter, smaller, more efficient and less prone to failure than the brush motor. As you might guess, the downside is that the price of brushless motors increases significantly over brushed motors. You won’t find brushless motors on inexpensive electric bikes. However, it is fairly easy to find brushless motors on bikes starting at $1,000.
The considerations for purchase are similar to those made on the battery page: if you plan to use the electric bike for short distances (10-15km) with little or no incline, then you may want to save a bit and get a bike with a brushless motor.