What is Torque in an Electric Bike?

By February 18, 2015July 7th, 2018Ask Optibike!, Jim's Blog, Optibike News

There has been a lot of discussion in the news lately about electric bikes and torque. For most people, the term “Torque” has little or no meaning.

In this first of 3 articles on torque,   I will go over the basics of torque. In Part 2, I will discuss torque and how it relates to horsepower and then in the  Part 3, I will compare the torque of Optibike and other leading brands of electric bicycles.

Why Torque Matters In An E bike

In an electric bicycle, torque is the ability to rotate the rear wheel. In a regular bicycle, this translates to the ability to rotate the pedals and crank arms. Higher torque will rotate the wheel easier and create more acceleration, especially from a stop. This means a bike with higher torque is easier to get going from a stop.

Image result for bicycle rider pushing on pedals

 What is Torque?

The general definition of torque is the force on an arm at a distance from a center of rotation. In the picture below, the distance is 1Meter and the force is 50Newtons, so the torque is 50 Newton Meters.

Image result for torque

Toque Equation

The general equation for torque is below.

Torque=Force X Distance

or T=F X D

In a standard  bicycle the rider pushes on the pedal to create a “Force” and  length of the crank arm is the distance. Crank arms are typically 175 mm or 7 inches long. If the rider weighs 200 pounds and stands on the pedal, the the torque is 1400 inch pounds as given by equation below:

Torque=Force X Distance

1400 inch pounds = 200 pounds X 7 inches

bicycle crank arm

Torque Units

In electric bikes, you will read about Torque in Metric Units (Newton Meters) or US units (inch pounds). You may also here torque in foot pounds.

A common torque for lower powered e bikes is 50 Newton Meters,which can be converted to 442 inch pounds or 36 foot pounds.

50 Newton Meters = 442 inch pounds = 36 foot pounds

In Part 2 I will discuss how torque multiplied by RPM make horsepower and how this affects your ride.

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