Torque is a key measurement of the performance of an electric bike, affecting how fast it accelerates, how well it climbs hills, and how responsive the rider feels it is. All riders looking at climbing hills with copious amounts of load on, or those looking for fast, responsive power, will be interested to learn about what torque is. This in-depth guide for professionals details the basics of e-bike torque, its parts, how to test it, and what to look out for when you’re buying an e-bike motor – as well as an overview of manufacturers and what sort of riding the motors will suit.
In the e-bike world, torque is the amount of rotational force the motor applies to your wheels. It’s measured in Newton-meters (Nm), and it is the single most important factor when it comes to how much heavy lifting your e-bike can do, such as getting up and going from a dead stop or getting up a hill. More torque means a more powerful power delivery, which makes it easier for the rider to deal with hills and have a more aggressive acceleration.
Torque is created in an e-bike motor through the passage of electricity between the motor's windings and magnets. This electrical current from the battery passes through the windings, producing a magnetic field that pushes the magnets away, making the motor turn. The torque output is linearly proportional to the current applied to the windings by the controller and the winding geometry of the motor.
The Core Factors of E-Bike Torque
An electric bike’s torque is not defined by motor power alone; it’s a confluence of three main contributors:
The Motor: Being the epicentre of the e-bike power system, everything about the motor, including its specification and design structure, totally predetermines the torque. E-bike motors come in two main types: hub motors, which are fitted inside the hub of the front or rear wheel, and mid-drive motors, which are located around the bottom bracket. Mid-drive motors are traditionally thought to be more torquey (or produce torque more efficiently) because they use the bike's gears.
The Controller: The controller functions as the brain of the e-bike by controlling the power flow from the battery to the motor. The quality of the programming of the controller determines how it delivers the torque, and if that is in a smooth and progressive manner or if it’s a more aggressive and sudden input.
The Battery: The motor's torque capacity depends on the voltage and discharge rate of the battery. A higher voltage and a larger current on-demand battery will help the motor to reach its maximum rated torque, especially when the bike is heavily loaded.
Evaluating E-Bike Torque Quality
Whether an e-bike’s torque is “good” or not is subjective and based on what it will be used for. Nevertheless, there are some general principles:
- Low Torque (30-40 Nm): This is for comfortable riding along flat terrains, for example, when leisurely riding on bike paths or for urban commuting.
- Moderate Torque (50-60 Nm): E-bikes with this range of torque will provide a significant increase in acceleration, surpass moderate hills, and transport lighter loads.
- High Torque (70 Nm plus): For performance riding, high torque is great for riding up steep hills, off-road, etc., and for carrying stuff on the bike. It’s also a category in which you’ll typically find electric mountain bikes and cargo bikes.
More than the quantity, the manner of delivering torque matters as well. A good system should offer seamless and intuitive power assistance that is responsive and unobtrusive, barely noticeable – the natural progression of the rider's own power. You can feel differences in the way torque is delivered only by test riding.
How to Choose an E-Bike by Torque
Bagging an e-bike with the right amount of torque for you takes plenty of thought about what you’ll want and how you’re planning on riding:
For the Urban Commuter: You only need a minimum torque of about 40-50 Nm to handle all terrain well. Power delivery here should be predictable and smooth for a comfortable, well-managed riding experience.
For the Hill Climber: For those of you who take on mountains every day going up a hill, surely some more torque, let’s say 60 Nm, would be really handy to push against your pedals every now and then, relieving you from that struggle.
For the Mountain Biker: Off-road riders require more torque to power up steep hills and through loose or soggy terrain. For a premium standard, a torque level of 70 Nm, and often much closer to 85 to 90 Nm, will provide the best possible experience.
For the Cargo Haulier: Carrying groceries, kids, or other heavy things requires a lot of torque to get up to speed and to keep that speed. The motor on your cargo e-bike should have a torque of at least 80 Nm.
Popular E-Bike Motor Brands
A number of brands have emerged as leaders at the forefront of the e-bike motor market, and all of these have made a name for themselves with a unique feature set:
Bosch: Renowned for its robust and dependable mid-drive motors, Bosch has a range of systems to suit most needs, from the casual riding Active Line to the high-performance, e-MTB-friendly Performance Line, with torques up to 85 Nm.
Shimano: Shimano is one of the big players within the bicycle industry, and their STEPS mid-drive systems provide excellent ride-feel, smoothness, and power. You have their state-of-the-art EP8 motor to thank, which boasts an impressive 85 Nm of torque.
Brose: The Brose motor is known for its whisper-quiet operation and gobs of power delivered in a smooth, intuitive way. Their Drive S Mag motor is capable of up to 90 Nm of torque and is found in plenty of e-MTBs.
Yamaha: Yamaha has been making e-bike motors for a long time, and their PW-X3 motor brings 85 Nm of torque to the fray with a very zesty character.
Bafang: Bafang gives you a lot of hub and mid-drive motors to choose from, and at a lower price point in a lot of cases. Their M620 mid-drive motor has enough muscle to churn out 160 Nm of torque, which is well-loved by high-speed and cargo bike builders.
Different E-Bike Uses and Torque Demands
There is no one torque figure for an electric bike. Each particular riding style and individual user will determine which is the best choice. A 130 lb roadie wanting a bit more boost is going to have far different torque needs than a 200 lb aggressive trail rider.
By knowing the underlying principles of torque and evaluating one's own requirements correctly, a rider can thus be able to make the right decision and get on an electric bike that will give them a much better cycling experience.
