Like so many components on e-bikes there are a multitude of options for motors, and one of the most common questions is whether to have a hub or mid mounted motor.
Mid motors are typically the more expensive motor option, with many moving parts. They are however a neater all in one package, and evenly distribute the motor weight between the front and rear wheels.
They really come into their own on dual suspension mountain bikes. On these bikes, it’s important to have light wheels that can easily move over rocks, so it is best to keep the weight on the bike frame, rather than in the wheel.
Whilst the drops outs can remain standard, the bottom bracket of the bike has to be specifically designed to fit the one brand of mid motor. It can be difficult to produce a lot of power out of a mid motor too, with such cramped space.
Mid motors have an inherent disadvantage, that isn’t commonly spoken about, is that the motor transfers all its power to the start of the drivetrain. This means that all the components in the drivetrain have to be upgraded to cater for the addition power of the motor. It is not wise to spec low quality drivetrain on a mid motor, as the chain, derailleur, shifter, cassette all have to cater for the additional load. There is a loss in efficiency with all those moving parts too.
Hub motors have the benefits in being incredibly efficient and the capacity for huge power, however perhaps the most important but unknown benefits is that fact that the hub motor applies its power after the drivetrain (cranks, chain, cassette and derailleur). When a hub motor it delivers power directly through the spokes to the tyre, and this adds to the efficiency. Bike frames and the drop outs specifically, should cater specifically for the motor as a lot of torque does go through the axle.
They are relatively cheaper to produce with fewer moving parts, but that being said there is a vast range of quality in hub motors.
Some of the negatives include the fact that a lot of weight is in the wheel, which is an issue for dual suspension mountain bikes, but otherwise it has little impact. Additionally, many people think it is much harder to change a wheel in the event of a flat, but typically this involves unplugging just one connection.
Question of front or rear hub motor, is a common one. Rear motors tend to provide the safest and most natural riding experience. You are used to the power coming from the rear wheel, so there are few surprises. Front hub motors, conversely can react quite poorly especially over uneven terrain or dirt, with a sudden loss in traction. Front hub motors tend to be chosen in applications where a bike brand is using an internally geared rear hub. The internal gear mechanism means that it is not possible to add the motor to the rear.