About the Electric Bike Professor Series

The Electric Bike Professor series is presented by Jim Turner, the designer of the Optibike and an engineer with more than 30 years of experience developing electric bike motors and drivetrains. Rather than promotional content, these videos are technical explanations — covering the physics and engineering principles that determine how an e-bike performs in the real world.

Topics covered in the series include e-bike torque, gear ratios, power bands, motor wattage, voltage, watt-hours vs amp-hours, and the difference between peak and continuous power. Each episode focuses on one concept and explains it from first principles, with specific numbers and comparisons to make the ideas concrete.

Click Here for the Video Playlist of The Electric Bike Professor Series

New episodes are added to the playlist as they are released. The summaries below cover the episodes currently available.

Episode Summaries

Episode 1: E-Bike Torque and Gear Ratios — What the Numbers Actually Mean

This episode explains what newton meters of torque mean in practical riding terms, and how gear ratios affect the torque delivered to the rear wheel. Using a straightforward example — a 100 Nm motor versus a 200 Nm motor, run through a 1:1 gear ratio and then a 2:1 gear ratio — Jim walks through exactly how much torque reaches the ground under each condition. The key insight is that a higher-torque motor means you can maintain usable rear-wheel torque in a higher gear, reducing the need to shift when a climb gets steeper.

• Key concept: Rear-wheel torque = motor torque × gear ratio
• Why it matters: Higher motor torque means less downshifting on hills
• Numbers used: 100 Nm (typical e-bike) vs. 200 Nm (high-torque e-bike), 1:1 and 2:1 gear ratios

Episode 2: Torque, Power Band, and Why They Affect How You Ride

Building on the torque episode, this video introduces the concept of the power band — the RPM range across which a motor can sustain its rated wattage output. At the US legal limit of 750 watts, a higher-torque motor reaches full power at a much lower cadence and maintains it across a wider range of speeds. A lower-torque motor requires higher cadence to reach the same wattage, which means more frequent shifting to stay in the effective power range. The practical result: a wider power band means less drivetrain wear, fewer shifts under load, and more consistent climbing performance.

• Key concept: Power band = the cadence range where a motor produces its rated output
• Why it matters: A wider power band reduces shifting, especially under climbing loads
• Side benefit: Less shifting under load extends cassette and chain life

Episode 3: What Is Power? Watts, Horsepower, and E-Bike Output Explained

This episode addresses a common source of confusion: what “power” actually means in the context of an electric bike. Jim explains that watts are the metric equivalent of horsepower (1 hp ≈ 750 W), and puts e-bike power figures in perspective — a 750-watt e-bike produces roughly the same energy as a small space heater, and a fraction of what a typical car engine generates. The episode also clarifies the physics definition of power: it is not simply force or movement, but the rate at which work is done — force applied over a distance, divided by the time it takes. This distinction matters when comparing motor ratings and understanding what different wattage figures mean on the road.

• Key concept: Power (watts) = work done per unit of time, not just force or speed alone
• Reference point: 750 W ≈ 1 horsepower; a small space heater runs at 1,500 W

Watch the Full Series

All available episodes are collected in the playlist linked above. New topics will be added as the series continues, covering additional subjects such as battery voltage, watt-hours vs. amp-hours, and peak versus continuous motor power ratings.

If you have a specific e-bike technical question you’d like covered in a future episode, send us a message!