Mid drive motors are becoming more popular on electric bicycles because they offer certain strengths over traditional in-wheel hub motors. These include:

• Improved frame balance front to rear and reduced frame flex

• The ability to leverage a larger cassette, internally geared hub or continuously variable transmission for optimizing RPM and efficiency

• Reduced unsprung weight (if the platform in question is a full suspension design)

• Easier maintenance for the drivetrain and wheels (as well as less wiring across the frame)

This last two benefits are key for off-road riding where trail maintenance and transporting the bike become a factor. I love mid-drive or centerdrive motors but want to acknowledge that they aren’t perfect for every situation… they do have some limitations and drawbacks worth considering and these include:

• Louder operation because they tend to be geared, they tend to produce the most noise in lower gears when the drive unit is spinning at higher RPM

• Increased wear on the chain or belt, sprocket teeth and derailleur because the motor is adding force to the drivetrain, often doubling and even tripling your own pedal input! Some mid-drive ebike systems do not offer shift detection to make the motor “ease off” at critical moments when changing gears and this further stresses components

• More active shifting and gear changing is required by the rider in order to start the bike, climb efficiently and reach maximum speeds due to limited RPM output at a wider range of operation vs. hub motors which connect directly to the wheel and don’t interface with gears

With this guide my intention is to offer a qualitative overview of the different brands of middrive ebike motors I’ve tested as of 2016 along with quantitative supporting points and specifications. Technology is evolving rapidly in the e-bike space and parts of this guide may become outdated so feel free to chime in using the comments at the end and I’ll make updates as needed. I’m not explicitly ranking the motors here but am starting out with some of the more popular, higher quality offerings. Bosch and Yamaha are two systems that get compared a lot and I’ve created a video with each of their stats and ride tests below to help demonstrate their differences: